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Glossary of Terms

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

0G - PTT, MTS, IMTS, AMTS are 0G standards.

0.5G - Autotel/PALM and ARP are 0.5G standards.

1G - First Generation. The first generation of cellular wireless (1G) was based on analog technology. The systems were designed only to carry voice technology. NMT, AMPS, Hicap, CDPD, Mobitex, DataTac are 1G standards.

2G - Second Generation.  Second-generation (2G) technology converts voice to digital data for transmission over the air and then back to voice. Most 2G systems provide 9.6–14.4-Kbps circuit-switched data service.  Examples would be GSM, iDEN, D-AMPS, CDMAOne, PDC, CSD, and PHS.

2.5G -
2.5G refers to technology that is added to a 2G network to provide packet-data service. In practice, 2.5G is synonymous with the GPRS technology that has been added to GSM networks. HSCSD, and WiDEN are other examples of 2.5G

2.75G - CDMA20001xRTT and EGPRS or EDGE (a further evolution of GPRS)

3G - Third Generation. Third-generation (3G) systems have been designed for both voice and data. By International Telecommunications Union (ITU) definition, 3G systems must provide a minimum of 144-Kbps packet-data service.  3G examples are: W-CDMA UMTS FOMA, CDM2000 1xEV, TD-SCDMA, and UMA standards.

3.5G - HSDPA is a 3.5G standard.

3.75G - HSUPA is a 3.75G standard.

3GPP - The 3rd Generation Partnership Project is a collaboration agreement that was established in December 1998. It's a co-operation between ETSI (Europe), ARIB/TTC (Japan), CCSA (China), ATIS (North America) and TTA (South Korea).  The scope of 3GPP is to make a globally applicable third generation (3G) mobile phone system specification within the scope of the ITU's IMT-2000 project. 3GPP specifications are based on evolved GSM specifications, now generally known as the UMTS system.  Note that 3GPP should not be confused with 3GPP2, which specifies standards for another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000.  3GPP standards are structured as Releases. Discussion of 3GPP thus frequently refers to the functionality in one release or another: Release 98 and earlier releases specify pre-3G GSM networks. Release 99 specify the first UMTS 3G networks, incorporating a CDMA air interface. Release 4 - originally Release 2000 - adds features including an All IP Core Network Release 5 introduces IMS and HSDPA.  Release 6 integrates operation with Wireless LAN networks and adds HSUPA.  Release 7 work towards better integration with wired networks.  Release 8 GSM Phase 2+ and UMTS Release 8, Handover capabilities for combinational services between WCDMA and WLAN networks.

75-Ohm Antenna/Cable Input - Compatible with any 75-ohm set-top/roof-top VHF/UHF antenna system as well as any residential/commercial CATV/CCTV system.


Acoustic Echo Canceller (AEC) - Full Duplex audio technology; used for the elimination of acoustically-coupled return echoes within a teleconference room. Note that all microphones connected to an AEC are active at all times. Consequently, as more microphones are added, the total transmitted noise level (caused by picking up room ambient noise) increases.

Access Method - In Local Area Networks, the technique and /or program code used to arbitrate the use of the communications medium by granting access selectively to individual stations.  Examples are CSMA/CD and Token Passing.

Access Point (AP) - A networking device that enables wireless stations to access the wired LAN infrastructure.

Adaptor - computer add-in board.  Network adapters are used to connect end user nodes to the network; each contains an interface to a specific type of workstation or system bus.  E.g.:  EISA, ISA, MCA, VME, etc.

 Adaptive Routing - A form of routing in which messages are forwarded through the network along the most cost-effective path currently available and are automatically rerouted if required by changes in the network topology (for example, if a circuit becomes disabled.)

Address - A designator defining the unique ID of a terminal, peripheral device or any other nodal component in a network.

ADM - Add-drop multiplexer - A main element of optical fiber networks. An add-drop multiplexer combines, or multiplexes, several lower-speed streams of data into a single beam of light. ADMs can be used both in long-haul core-networks and in shorter distance metro networks, although in recent years (2002-04) most ADM sales have been in metro networks due to the high cost required to scale the technology to high data rates (wavelength division multiplexing, better known as DWDM, is more popular in the core).

Ad-hoc Network - An ad-hoc network is a wireless network created for a specific purpose, typically in a spontaneous manner without use of an access point.  The principle characteristic of an ad-hoc network is that the act of creating and dissolving the network is sufficiently straightforward and convenient so as to be achievable by non-technical users of the network facilities.

ADSL - Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide.  ADSL uses two separate frequency bands. The band from 25.875 kHz to 138 kHz is used for upstream communication, while 138 kHz - 1104 kHz is used for downstream communication.

The ADSL Standards are as follows:

Standard name Standard type Downstream rate Upstream rate
ANSI T1.413-1998 Issue 2 ADSL 8 Mbit/s 1.0 Mbit/s
ITU G.992.1 ADSL (G.DMT) 8 Mbit/s 1.0 Mbit/s
ITU G.992.2 ADSL Lite (G.Lite) 1.5 Mbit/s 0.5 Mbit/s
ITU G.992.3/4 ADSL2 12 Mbit/s 1.0 Mbit/s
ITU G.992.3/4 Annex J ADSL2 12 Mbit/s 3.5 Mbit/s
ITU G.992.5 ADSL2+ 24 Mbit/s 1.0 Mbit/s
ITU G.992.5 Annex L ADSL2+ 24 Mbit/s 3.5 Mbit/s

Adware - Adware or advertising-supported software is any software package which automatically plays, displays, or downloads advertising material to a computer after the software is installed on it or while the application is being used.

AES - Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the US government, and is expected to be used worldwide and analyzed extensively, as was the case with its predecessor, the Data Encryption Standard (DES). It was adopted by National Institute of Standards and Technology (NIST) as US FIPS PUB 197 in November 2001 after a 5-year standardization process (see Advanced Encryption Standard process for more details).  The cipher was developed by two Belgian cryptographers, Joan Daemen and Vincent Rijmen, and submitted to the AES selection process under the name "Rijndael", a portmanteau comprised of the names of the inventors. Rijndael can be pronounced "Rhine dahl", a long "i" and a silent "e".

Alias, Aliasing - A false signal produced by the analog-to-digital sampling process. Often caused by failure to observe the Nyquist criterion and can create artifacts which are subjectively. A common form of aliasing is a stair-stepped appearance along diagonal and curved lines.

Algorithm - The specific formula or procedure used to compress and decompress digital audio and video.

American National Standards Institute (ANSI) -  An organization that coordinates, develops, and publishes standards Standards Institute for use in the United States.  It also represents the United States in  the International Standards Organization (ISO).

AMPS Analog - Advanced Mobile Phone Service (AMPS) has been available since 1976 when it was first used on a trial basis in the U.S. and then commercialized in the early 1980s. With AMPS, each channel can handle a single voice call. In order to add more capacity to an AMPS cellular system, more channels per cell site or more cell sites must be added.

AMR - Adaptive Multi-Rate is an Audio data compression scheme optimized for speech coding. AMR is adopted as the standard speech codec by 3GPP. The codec has eight bit rates, 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 Kbit/s. The bitstream is based on frames which contain 160 samples and are 20 milliseconds long. AMR uses different techniques, such as Algebraic Code Excited Linear Prediction (ACELP), Discontinuous Transmission (DTX), voice activity detection (VAD) and comfort noise generation (CNG). The idea to use various modes arises from the network conditions. If the channel is bad, source coding is reduced and channel coding is increased. This improves the quality and robustness of the network. In the particular case of AMR this improvement is somewhere around 4-6 dB S/N for useable communication. The usage of AMR requires optimized link adaptation that selects the best codec mode to meet the local radio channel and capacity requirements. The new intelligent system allows the network operator to prioritize capacity or quality per base station.

Analog video - A video signal represented in a waveform by physical variables such as voltage and current.

ANSI-136 - is called TDMA in the Americas. See TDMA Standards, D-AMPS.

ANSI-41 - ANSI-41 is a protocol standardized by the Telecommunications Industry Association (TIA) and the American National Standards Institute (ANSI) for enabling cdmaOne, cdma2000 and TDMA subscribers to roam between different wireless service operators’ systems to make and receive voice calls.

ANSI X3T9.5 - A sub-committee sponsored by ANSI, which sets system interconnection standards, including the specifications for Fiber Distributed  Data Interface (FDDI).

Antialiasing - A method for smoothing the jagged edges (stair steps) often seen in graphics or video. The method reduces the jagged edges by placing intermediate shades of color or gray around the steps.

AS - An Application Server is a server computer in a computer network dedicated to running certain software applications. The term also refers to the software installed on such a computer to facilitate the serving (running) of other applications.  Following the success of the Java platform, the term application server often refers to a J2EE application server. WebSphere (IBM), Oracle Corporation (Application Server 10g) and WebLogic (BEA) are the better known commercial J2EE application servers. The JOnAS application server, developed by the ObjectWeb consortium, is the first non-commercial, open source application server to have reached the official certification of compliance with J2EE. The programming language used is Java. The web modules are servlets and JavaServer Pages (JSP), and business logic is built into Enterprise JavaBeans (EJB). The Java 2 Platform, Enterprise Edition (J2EE) provides standards for containing the web components. Tomcat from Apache and JOnAS from ObjectWeb are typical of containers to put these modules into. Both organizations provide the code freely and openly (open source).  JSP is a Servlet from Java that execute in a web container--the Java equivalent of CGI scripts. JSP is a way to create HTML pages by embedding references to the server logic within the page. HTML coders and Java programmers can work side by side by referencing each other's code within their own. JavaBeans are the independent class components of the Java2 architecture from Sun Microsystems. 

The term application server has also been applied to various non-J2EE and non-Java offerings. For example, with the rising popularity of .NET, Microsoft can claim to deliver an application server. Additional open source and commercial application servers are available from other vendors. Some examples are the Base4 Server and Zope. Contrary to prior versions of this entry, Microsoft's Windows Communication Foundation is not an application server, but rather a framework for communication (middleware). 

Application server products typically bundle middleware to enable applications to intercommunicate with various qualities of service — reliability, security, non-repudiation, and so on. Application servers also provide an API to programmers, so that they don't have to be concerned with the operating system or the huge array of interfaces required of a modern web-based application. Communication occurs through the web in the form of HTML and XML, as a link to various databases, and, quite often, as a link to systems and devices ranging from huge legacy applications to small information devices, such as an atomic clock or a home appliance.  Portals are a very common application server mechanism by which organizations can manage information. They provide a single point of entry for all users, they can access Web services transparently from any device, and they are highly flexible. Portals can work inside or outside of the organization, and they can attach themselves to any part of it.  This term is widely used as a buzzword in the following fields:
bullet Distributed computing — denoting a computer running some part of a distributed computation task
bullet Software components — denoting a "component farm", which is a computer loaded with software components, ready to answer calls for usage
bullet Web services — denoting a machine running applications which will answer interface calls over HTTP in an XML format

Artifact - Spurious effects or imperfections introduced into a signal as a result of digital signal processing.  An unintended, unwanted visual abbreviation in a video image.

Aspect ratio - The ratio of the width of an image to its height.  For television, this is typically 4:3.

ASF - Active Streaming Format. A Microsoft file format for digital video playback over the Internet, or on a standalone computer. Kind of a wrapper around any of a number of compression types, including MPEG. Part of Netshow, a proprietary streaming media solution from Microsoft. Biggest competitor is Real Networks. While this 'wrapper' support many standard formats, ASF files are themselves proprietary.

ASIC - Pronounced ay-sik, and short for Application-Specific Integrated Circuit, a chip designed for a particular application (as opposed to the integrated circuits that control functions such as RAM in a PC). ASICs are built by connecting existing circuit building blocks in new ways. Since the building blocks already exist in a library, it is much easier to produce a new ASIC than to design a new chip from scratch.  ASICs are commonly used in automotive computers to control the functions of the vehicle and in PDAs.

ATM - Asynchronous Transfer Mode.  Very high speed transmission technology.  ATM is a high bandwidth, low-delay, connection oriented, cell (or fixed size packet) switching and multiplexing technique.  When purchasing ATM service, you generally have a choice of four different types of service: constant bit rate (CBR): specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line. variable bit rate (VBR): provides a specified throughput capacity but data is not sent evenly. This is a popular choice for voice and videoconferencing data. available bit rate (ABR): provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free. unspecified bit rate (UBR): does not guarantee any throughput levels. This is used for applications, such as file transfer, that can tolerate delays.

ATM Adaptation Layer (AAL) - AAL1, AAL2, AAL3/4, and AAL5 are the different types of the ATM adaptation Layer.

ATSC - Advanced Television Systems Committee.  Formed by the Joint Committee on Inter-Society Coordination (JCIC) to establish voluntary standards for Advanced TV (ATV) systems.  The ATSC focuses on digital television, interactive systems and broadband multimedia communications standards.  Membership is open to North and South American including the Caribbean entities.  The main ATSC standards for DTV are 8-VSB, which is used in the transmission of video data, MPEG-2 for video signal compression, and Dolby Digital for audio coding.

AUC - The Authentication Centre or AUC is a function to authenticate each SIM card that attempts to connect to the GSM core network (typically when the phone is powered on). Once the authentication is successful, the HLR is allowed to manage the SIM and services described above. An encryption key is also generated that is subsequently used to encrypt all wireless communications (voice, SMS, etc.) between the mobile phone and the GSM core network. If the authentication fails, then no services are possible from that particular combination of SIM card and mobile phone operator attempted. There is an additional form of identification check performed on the serial number of the mobile phone described in the EIR section below, but this is not relevant to the AUC processing. Proper implementation of security in and around the AUC is a key part of an operator's strategy to avoid SIM cloning. The AUC does not engage directly in the authentication process, but instead generates data known as triplets for the MSC to use during the procedure. The security of the process depends upon a shared secret between the AUC and the SIM called the Ki. The Ki is securely burned into the SIM during manufacture and is also securely replicated onto the AUC. This Ki is never transmitted between the AUC and SIM, but is combined with the IMSI to produce a challenge/response for identification purposes and an encryption key called Kc for use in over the air communications.

Audio 1 & 2 Inputs - Regular phono jacks designed to accompany the S-Video and composite video inputs (respectively); these inputs accept a wide variety of audio sources.

Audio Buffer - A buffer in the target system decoder for storage of compressed audio data.  Typically used to hold audio data for synchronization with its corresponding incoming video data.

Audio Decoder - That part of a decoder responsible for decompressing the audio bit stream as specified by Part 3 of the MPEG standard.

Audio Encoder - That part of an encoder responsible for compressing the audio bit stream as specified by Part 3 of the MPEG standard.

Audio Input with Loop-Through Output - Regular phono jacks designed to accompany the SVGA/VGA, S-Video, and composite video inputs. These inputs accept a wide variety of audio sources.

Audio Masking - A compression technique that drops out one audio signal that cannot be perceived by the human ear because of the presence of another audio signal.

Audio/Video Input Jacks - For fast and easy hookup of peripheral devices such as VCRs, and laser disc players.

Audio/Video Muting - Automatically detects the loss of RF signal. When this happens, video defaults to a blue or black background and audio mutes. The units automatically return to their original settings when the signal is resumed.

Audio only conference add-ins - The ability to add another site into a video conference via an audio connection only. This feature uses a regular phone line connected to the codec to conference in someone who is not near a video site but needs to be part of the conversation.

Audio Stream - A bit sequence of compressed digital audio.

Audio Teleconferencing - Two-way electronic voice communication between two or more people at two or more locations.

Auto Power On - Forces the default power setting to the ON position, preventing sets from being turned off while in use. Additionally, this feature allows all sets to be controlled from a single circuit breaker and forces the set to turn back on automatically after a power interruption.

Automatic Mode Detection - This feature allows the television to detect different video modes, learn screen geometry, and automatically recall screen settings (this feature along with the ability to adjust horizontal and vertical scaling, makes your TV display compatible with most computer software platforms.

Autonomous System - In the Internet, an autonomous system (AS) is a collection of IP networks and routers under the control of one entity (or sometimes more) that presents a common routing policy to the Internet. See RFC 1930 for additional detail on this updated definition. Originally, the definition required control by a single entity, typically an Internet service provider or a very large organization with independent connections to multiple networks, that adhere to a single and clearly defined routing policy. See RFC 1771, the original definition (now obsolete) of the Border Gateway Protocol. The newer definition of RFC 1930 came into use because multiple organizations can run BGP using private AS numbers to an ISP that connects all those organizations to the Internet. Even though there are multiple autonomous systems supported by the ISP, the Internet only sees the routing policy of the ISP. That ISP must have a public, registered ASN. A unique AS number (or ASN) is allocated to each AS for use in BGP routing. With BGP, AS numbers are important because the ASN uniquely identifies each network on the internet.

A/V - Audio/Video.

AVI - Audio Video Interleaved. A Microsoft format for digital audio and video playback from Windows 3.1 Somewhat cross-platform, but mostly a Windows format. Has been replaced by the ASF format, but still used by some multimedia developers.  



B2BUA - A Back-to-back User Agent is primarily used to interface an IP Multimedia Subsystem (IMS) network to other networks. The B2BUA acts as a proxy to both ends of a SIP call. The B2BUA is responsible for handling all SIP signaling between both ends of the call, from call establishment to termination. Each call is tracked from beginning to end, allowing the operators of the B2BUA to offer value-added features to the call. To SIP clients, the B2BUA acts as a User Agent server on one side and as a User Agent client on the other (back-to-back) side. The basic implementation of a B2BUA is defined in RFC 3261. The B2BUA provides the following functionality:

bullet call management (billing, automatic call disconnection, call transfer, etc.)
bullet network interworking (perhaps with protocol adaptation)
bullet hiding of network internals (private addresses, network topology, etc.)
Because it maintains call state for all SIP calls it handles, failure of a B2BUA affects all these calls. A Signaling gateway, part of a Session Border Controller, is a good example of a B2BUA.

Banding - The presence of extraneous lines.

Bandwidth - A measure of the amount of data that can fit on a communication channel. In analog communications bandwidth is the width, typically measured in Hertz (or cycles per seconds), of a frequency band f2 − f1.  In digital communications, bandwidth is typically measured in bits per second.  The higher the bandwidth, the sharper the picture; low bandwidth can cause a fuzzy picture.  The following is a list of devices bandwidth:


Modems  (note: serial, 1 start bit, 8 data bits, 1 stop bit: therefore 10 bits needed to transmit each byte. The exception is 110 baud which uses 2 stop bits or 11 bits per byte.)

Modem 110 baud 110 bit/s 10 B/s
Modem 300 baud (V.21) 300 bit/s 30 B/s
Modem Bell 103 (Bell 103) 300 bit/s 30 B/s
Modem 1200 (V.22) 1.2 kbit/s 120 B/s
Modem Bell 212A (Bell 212A) 1.2 kbit/s 120 B/s
Modem 2400 (V.22bis) 2.4 kbit/s 240 B/s
Modem 9600 (V.32) 9.6 kbit/s 960 B/s
Modem 14.4k (V.32bis) 14.4 kbit/s 1,440 B/s
Modem 19.2k (V.32terbo) 19.2 kbit/s 1,920 B/s
Modem 28.8k (V.34) 28.8 kbit/s 2,880 B/s
Modem 33.6k (V.34plus/V.34bis) 33.6 kbit/s 3,360 B/s
Modem 56k* (V.90) (downstream) 56.0 kbit/s 5.6 kB/s
Modem 56k* (V.90) (upstream) 33.6 kbit/s 3.36 kB/s
Modem 56k* (V.92) (downstream) 56.0 kbit/s 5.6 kB/s
Modem 56k* (V.92) (upstream) 48.0 kbit/s 4.8 kB/s


64k ISDN 64.0 kbit/s 8 kB/s
128k dual-channel ISDN 128.0 kbit/s 16 kB/s
ISDN-PRI 24x64K 1536 kbit/s 192 kB/s
ISDN-PRA 30x64K 1920 kbit/s 240 kB/s

Computer interfaces (internal)

ISA 08-Bit/4.77MHz 38.66 Mbit/s 4.83 MB/s
ISA 16-Bit/8.33MHz 134.66 Mbit/s 16.85 MB/s
PCI 32-bit/33MHz 1066.66 Mbit/s 133.33 MB/s
PCI Express (x1 link) 2500 Mbit/s 250 MB/s
PCI 64-bit/33MHz 2133.33 Mbit/s 266.66 MB/s
PCI 32-bit/66MHz 2133.33 Mbit/s 266.66 MB/s
AGP 1x 2133.33 Mbit/s 266.66 MB/s
AGP 2x 4266.66 Mbit/s 533.33 MB/s
PCI 64-bit/66MHz 4266.66 Mbit/s 533.33 MB/s
PCI-X DDR 16-bit 4266.66Mbit/s 533.33 MB/s
PCI Express (x4 link) 10000 Mbit/s 1000 MB/s
AGP 4x 8533.33 Mbit/s 1066.66 MB/s
PCI-X 133 8533.33 Mbit/s 1066.66 MB/s
PCI-X QDR 16-bit 8533.33 Mbit/s 1066.66 MB/s
InfiniBand 10.00 Gbit/s 1.25 GB/s
PCI Express (x8 link) 20.00 Gbit/s 2.0 GB/s
AGP 8x 17.066 Gbit/s 2.133 GB/s
PCI-X DDR 17.066 Gbit/s 2.133 GB/s
PCI Express (x16 link) 40.0 Gbit/s 4.0 GB/s
PCI-X QDR 34.133 Gbit/s 4.266 GB/s
HyperTransport (800MHz, 16-pair) 51.2 Gbit/s 6.4 GB/s
HyperTransport (1GHz, 16-pair) 64.0 Gbit/s 8.0 GB/s
Note that PCI Express lanes use a 10b/8b encoding scheme

Computer interfaces (drive)

SCSI 1 12.0 Mbit/s 1.5 MB/s
Fast SCSI 2 80 Mbit/s 10 MB/s
Fast Wide SCSI 2 160 Mbit/s 20 MB/s
Ultra DMA ATA 33 264 Mbit/s 33 MB/s
Ultra Wide SCSI 40 320 Mbit/s 40 MB/s
Ultra DMA ATA 66 528 Mbit/s 66 MB/s
Ultra-2 SCSI 80 640 Mbit/s 80 MB/s
Ultra DMA ATA 100 800 Mbit/s 100 MB/s
Ultra DMA ATA 133 1064 Mbit/s 133 MB/s
Serial ATA (SATA-150) 1200 Mbit/s 150 MB/s
Ultra-3 SCSI 160 1280 Mbit/s 160 MB/s
Fiber Channel 800 or 1600 Mbit/s 100 or 200 MB/s
Serial ATA (SATA-300) 2400 Mbit/s 300 MB/s
Ultra-320 SCSI 2560 Mbit/s 320 MB/s
Ultra-640 SCSI 5120 Mbit/s 640 MB/s

Computer interfaces (external)

Serial RS-232 commonly 9.6 kbit/s 960 B/s
Serial RS-232 max 230.4 kbit/s 23.0 kB/s
USB Low Speed 1536 kbit/s 192 kB/s
Parallel (Centronics) 8.0 Mbit/s 1.0 MB/s
Serial RS-422 max 10.0 Mbit/s 1.25 MB/s
USB Full Speed 12.0 Mbit/s 1.5 MB/s
FireWire (IEEE 1394) 100 100 Mbit/s 12.5 MB/s
FireWire (IEEE 1394) 200 200 Mbit/s 25 MB/s
FireWire (IEEE 1394) 400 400 Mbit/s 50 MB/s
USB Hi-Speed 480 Mbit/s 60 MB/s
FireWire (IEEE 1394b) 800 800 Mbit/s 100 MB/s


IrDA-Control 72 kbit/s 9 kB/s
IrDA-SIR 115.2 kbit/s 14 kB/s
802.15.4 (2.4GHz) 250 kbit/s 31.25 kB/s
Bluetooth 1.1 1 Mbit/s 125 kB/s
802.11 legacy 0.125 2 Mbit/s 250 kB/s
Bluetooth 2 3 Mbit/s 375 kB/s
IrDA-FIR 4 Mbit/s 500 kB/s
RONJA free source optical wireless 10.00 Mbit/s 1.25 MB/s
802.11b DSSS 0.125 11 Mbit/s 1.375 MB/s
802.11b+ non-standard DSSS 0.125 44.0 Mbit/s 5.5 MB/s
802.11a 0.75 54.00 Mbit/s 6.75 MB/s
802.11g DSSS 0.125 54.00 Mbit/s 6.75 MB/s
802.11n 540 Mbit/s 67.5 MB/s

Mobile telephone interfaces

GSM CSD 2400 to 14400 bit/s 300 to 1800 B/s
HSCSD upstream 14.4 kbit/s 1800 B/s
HSCSD downstream 43.2 kbit/s 5.4 kB/s
GPRS upstream 28.8 kbit/s 3.6 kB/s
GPRS downstream 57.6 kbit/s 7.2 kB/s
UMTS downstream 1920 kbit/s 240 kB/s

Wide area network

DS0 64 kbit/s 8 kB/s
Satellite Internet upstream 64kbit/s to 1Mbit/s 8 kB/s to 128 kB/s
Satellite Internet downstream 128kbit/s to 16Mbit/s 16kB/s to 2 MB/s
Frame Relay 8 kbit/s to 45 Mbit/s 1 kB/s to 5.625 MB/s
G.SHDSL 2.3040 Mbit/s 0.288 MB/s
SDSL 64 kbit/s to 4.608 Mbit/s 8 kB/s to 0.576 MB/s
G.Lite (aka ADSL Lite) upstream 512 kbit/s 64 kB/s
G.Lite (aka ADSL Lite) downstream 1.5 Mbit/s 192 kB/s
ADSL upstream 64 kbit/s to 1024 kbit/s 8 kB/s to 128 kB/s
ADSL downstream 256 kbit/s to 8 Mbit/s 32 kB/s to 1 MB/s
ADSL2 upstream 64 kbit/s to 3.5 Mbit/s 8 kB/s to 448 kB/s
ADSL2 downstream 256 kbit/s to 12 Mbit/s 32 kB/s to 1.5 MB/s
ADSL2Plus upstream 64 kbit/s to 3.5 Mbit/s 8 kB/s to 448 kB/s
ADSL2Plus downstream 256 kbit/s to 24 Mbit/s 32 kB/s to 3.0 MB/s
DOCSIS (Cable Modem) upstream 128 kbit/s to 8 Mbit/s 16 kB/s to 1 MB/s
DOCSIS (Cable Modem) downstream 384 kbit/s to 24 Mbit/s 48 kB/s to 3 MB/s
DS1/T1 1.544 Mbit/s 192.5 kB/s
E1 2.048 Mbit/s 256 kB/s
E2 8.448 Mbit/s 1.056 MB/s
E3 34.368 Mbit/s 4.296 MB/s
DS3/T3 ('45 Meg') 44.736 Mbit/s 5.5925 MB/s
STS-1/EC-1/OC-1/STM-0 51.840 Mbit/s 6.48 MB/s
VDSL (symmetry optional) 12 Mbit/s to 100 Mbit/s 1.5 MB/s to 12.5 MB/s
VDSL2 (symmetry optional) 12 Mbit/s to 250 Mbit/s 1.5 MB/s to 31.25 MB/s
LR-VDSL2 (4 to 5 km [long-]range) (symmetry optional) 1 Mbit/s to 4 Mbit/s 128 kB/s to 512 kB/s
OC-3/STM-1 155.52 Mbit/s 19.44 MB/s
OC-12/STM-4 622.08 Mbit/s 77.76 MB/s
OC-48/STM-16 2.448320 Gbit/s 306.104 MB/s
OC-192/STM-64 9.953280 Gbit/s 1.24416 GB/s
10 Gigabit Ethernet WAN PHY 9.953280 Gbit/s 1.24416 GB/s
10 Gigabit Ethernet LAN PHY 10 Gbit/s 1.25 GB/s
OC-768/STM-256 39.813120 Gbit/s 4.97664 GB/s

Local area network

LocalTalk 230.4 kbit/s 28.8 kB/s
ARCNET (Standard) 2.5 Mbit/s 0.3125 MB/s
Token Ring (Original) 4.16 Mbit/s 0.52 MB/s
Ethernet (10base-X) 10 Mbit/s 1.25 MB/s
Token Ring (Later) 16 Mbit/s 2.0 MB/s
Fast Ethernet (100base-X) 100 Mbit/s 12.5 MB/s
FDDI 100 Mbit/s 12.5 MB/s
Gigabit Ethernet (1000base-X) 1 Gbit/s 125 MB/s
10 Gigabit Ethernet (10Gbase-X) 10 Gbit/s 1250 MB/s

Memory Interconnect Buses / RAM

PC66 SDRAM 4264 Mbit/s 533 MB/s
PC100 SDRAM 6400 Mbit/s 800 MB/s
PC133 SDRAM 8528 Mbit/s 1066 MB/s
PC1600 DDR-SDRAM 12.8 Gbit/s 1.6 GB/s
PC2100 DDR-SDRAM 16.8 Gbit/s 2.1 GB/s
PC2700 DDR-SDRAM 21.6 Gbit/s 2.7 GB/s
PC3200 DDR-SDRAM 25.6 Gbit/s 3.2 GB/s
PC800 RDRAM (single-channel) 12.8 Gbit/s 1.6 GB/s
PC800 RDRAM (dual-channel) 25.6 Gbit/s 3.2 GB/s
PC1066 RDRAM (single-channel) 16.8 Gbit/s 2.1 GB/s
PC1066 RDRAM (dual-channel) 33.6 Gbit/s 4.2 GB/s
PC1200 RDRAM (single-channel) 19.2 Gbit/s 2.4 GB/s
PC1200 RDRAM (dual-channel) 38.4 Gbit/s 4.8 GB/s
PC2-3200 DDR2-SDRAM 25.6 Gbit/s 3.2 GB/s
PC2-4200 DDR2-SDRAM 34.136 Gbit/s 4.267 GB/s
PC2-5400 DDR2-SDRAM 42.664 Gbit/s 5.333 GB/s
PC2-6400 DDR2-SDRAM 51.2 Gbit/s 6.4 GB/s
PC2-8500 DDR2-SDRAM 68.264 Gbit/s 8.533 GB/s
2005-Feb Prototype DDR3-SDRAM ~68.224 Gbit/s ~8.528 GB/s

Bandwidth On Demand - using telecommunications equipment to "dial-up" the bandwidth you need.  In circuit switched networks, the use of Inverse Multiplexers (or IMUX) to combine 2 or more fixed bit rate channels (56/64Kbps channels) is an example of bandwidth on demand.  Bandwidth on demand is typically done with digital circuits (digital circuits are easier to combine).  In packet or cell switched networks (e.g. ATM), the same concept applies, but the method of achieving bandwidth on demand is different.

Baseband - All signals are comprised of a whole range of different frequencies added up together. In telecommunications in particular, it is often the case that those parts of the signal which are at low frequencies are 'copied' up to higher frequencies for transmission purposes, since there are few communications media that will pass low frequencies without distortion. Then, the original, low frequency components, are referred to as the baseband signal. Typically, the new, high frequency copy is referred to as the 'RF' (radio frequency) signal, although it need not be at the particular frequencies set aside for radio. More precisely, a signal "at baseband" is usually considered to comprise all relevant frequencies from 0Hz up to the highest frequency component in the signal with significant power. The signal is then usually modulated in order that it may be transmitted. Modulation results in shifting the signal up to much higher (RF) frequencies than it originally spanned. A key consequence of this process is that, usually, the range of frequencies the signal spans (its spectral bandwidth) is doubled. Thus, the RF bandwidth of a signal is usually twice its baseband bandwidth. Steps may be taken to reduce this effect, such as filtering the RF signal prior to transmission.

BCP - The Bridge Control Protocol is a support feature described in RFC 3518. The Cisco implementation of BCP is a VLAN infrastructure that does not require the use of sub-interfaces to group Ethernet 802.1Q trunks and the corresponding PPP links. This approach enables users to process VLAN encapsulated packets without having to configure sub-interfaces for every possible VLAN configuration.

BGAN - Broadband Global Area Network is a future Inmarsat network comprising satellites and land earth stations; permits data speeds up to 432 kbps.

BGP - The Border Gateway Protocol is the core routing protocol of the Internet. It works by maintaining a table of IP networks or 'prefixes' which designate network reachability between autonomous systems (AS). It is described as a path vector protocol. BGP does not use technical metrics, but makes routing decisions based on network policies or rules. BGP version 4, is specified in RFC 4271 (as per Jan 2006). This RFC obsoletes RFC 1771

BGP supports classless inter-domain routing and uses route aggregation to decrease the size of routing tables. Since 1994, version four of the protocol has been in use on the Internet; all previous versions are considered obsolete.

BGP was created to replace the Exterior Gateway Protocol (EGP) routing protocol to allow fully decentralized routing in order to allow the removal of the NSFNET Internet backbone network. This allowed the Internet to become a truly decentralized system. Very large private IP networks can also make use of BGP; an example would be the joining of a number of large Open Shortest Path First (OSPF) networks where OSPF by itself would not scale to size. Another reason to use BGP would be multi-homing a network for better redundancy. Most Internet users do not use BGP directly. However, since most Internet service providers must use BGP to establish routing between one another, it is one of the most important protocols of the Internet.

Compare and contrast this with Signaling System 7, which is the inter-provider core call setup protocol on the PSTN.  A BGP peer uses a simple Finite State Machine (FSM) to make decisions in its operations with other BGP peers. The FSM consists of six states: Idle, Connect, Active, OpenSent, OpenConfirm, and Established. A BGP peer will transition the TCP connection to another peer between these states as it attempts to establish and maintain a session with that peer.  BGP uses the following criteria to determine the path to use (from top to bottom): 1-) An explicit route (i.e. not a default route) for the next-hop router must exist in the routing table.  2-) Prefer the path with the highest weight (Only on Cisco routers).  3-) Prefer the path with the highest local preference.  4-) Prefer any BGP originated on this router.  5-) Prefer the route with the shortest AS path.  6-) prefer the route with the lowest origin (IGP < EGP < ?).  7-) Prefer the path with the lowest MED (Multi exit discriminator).  8-) Prefer external paths to internal paths.  9-) Prefer the path with the lowest IGP metric to the next hop.  10-) If all remaining paths are external choose the oldest one.  11-) Prefer the next hop router with the lowest BGP ID.  BGP problems and mitigation: 1-) A feature known as "damping" is built into BGP to mitigate the effects of route flapping. Flapping of routes can be caused by WAN / WLAN links or physical interfaces mending and breaking or by misconfigured or mismanaged routers. Without damping, routes can be injected and withdrawn rapidly from routing tables, possibly causing a heavy processing load on routers thus affecting overall routing stability.  2-) One of the largest problems faced by BGP, and indeed the Internet infrastructure as a whole, comes from the growth of the Internet routing table.

BI - Business Intelligence is a broad category of business processes, application software and other technologies for gathering, storing, analyzing, and providing access to data to help users make better business decisions.  Most companies collect a large amount of data from their business operations. To keep track of that information, a business and would need to use a wide range of software programs , such as Excel, Access and different database applications for various departments throughout their organization. Using multiple software programs makes it difficult to retrieve information in a timely manner and to perform analysis of the data.  The term Business Intelligence (BI) represents the tools and systems that play a key role in the strategic planning process of the corporation. These systems allow a company to gather, store, access and analyze corporate data to aid in decision-making. Generally these systems will illustrate business intelligence in the areas of customer profiling, customer support, market research, market segmentation, product profitability, statistical analysis, and inventory and distribution analysis to name a few.

BICC - The Bearer Independent Call Control is a signaling protocol based on N-ISUP that is used to support narrowband ISDN service over a broadband backbone network without interfering with interfaces to the existing network and end-to-end services.  Specified by the International Telecommunications Union - Telecommunications Standardization Sector (ITU-T) in recommendation Q.1901, BICC was designed to be fully compatible with existing networks and any system capable of carrying voice messages. BICC supports narrowband ISDN services independently of bearer and signaling message transport technology. ISUP messages carry both call control and bearer control information, identifying the physical bearer circuit by a Call Instance Code (CIC). The narrowband ISDN service also uses a CIC of a lower range referred to as the Circuit Identification Code.  However, CIC is specific to time-division multiplexed (TDM) networks. BICC was developed to be interoperable with any type of bearer, such as those based on asynchronous transfer mode (ATM) and Internet Protocol (IP) technologies, as well as TDM. BICC separates call control and bearer connection control, transporting BICC signaling independently of bearer control signaling.  The actual bearer transport used is transparent to the BICC signaling protocol - BICC has no knowledge of the specific bearer technology, which is referenced in the binding information.  The ITU announced the completion of the second set of BICC protocols (BICC Capability Set 2, or CS 2) in July 2001; these are expected to help move networks from the current model - which is based on public-switching systems - to a server-based model.  The BICC deployment architecture comprises a server, proxy, and a media gateway to support the current services over networks based on circuit-switched, ATM, and Internet Protocol (IP) technologies, including third-generation wireless.  According to the ITU, the completion of the BICC protocols is a historic step toward broadband multimedia networks, because it will enable the seamless migration of circuit-switched TDM networks to high-capacity broadband multimedia networks.  The Third Generation Partnership Project (3GPP) has included BICC CS 2 in the Universal Mobile Telecommunications Service (UMTS) release 4. Among the future ITU-T plans for BICC are the inclusion of more advanced service support and more utilization of proxies, such as the Session Initiation Protocol (SIP) proxy.

Bit rate - The speed of a communication channel.  typically expressed in bits per seconds (bps).  For example modems that follow the V.90 standard, have a bit rate of 56kbps (56,000 bits per second).

Block - An 8 x 8 set of pixels.  It is the most basic element of a video picture, and is represented as a set of values that defines either a luminance (Y) block or a chrominance (Cb or Cr) block.

Block-based Motion Compensation - A technique used to reduce temporal redundancy.

BPM - Business Process Management, is the practice of improving the efficiency and effectiveness of any organization by automating the organization's business processes. BPM used to be also know as Business Process Reengineering (BPR).  Many companies have business processes that are unique to its business model. Since these processes tend to evolve over time as the business reacts to market conditions, the BPM solution you choose must be easily adaptable to the new conditions and requirements and continue to be a perfect fit for the company.  In order to use BPM effectively, organizations must stop focusing exclusively on data and data management, and adopt a process-oriented approach that makes no distinction between work done by a human and a computer.

BRA - Basic Rate Access.  A European term for BRI.

BRI - Basic Rate Interface.  BRI is an ISDN interface with 2B+D channels.  Each channel is 64Kbps full duplex ideal for isochronous traffic like voice and video.  See ISDN BRI.

Bridge - 1. Device used to interconnect three or more telecommunications channels such as telephone lines, to permit simultaneous, two-way communication among all points that have been interconnected. 2. A device that connects one local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or Token Ring). If a data unit on one LAN is intended for a destination on an interconnected LAN, the bridge forwards the data unit to that LAN; otherwise, it passes it along on the same LAN.

Broadband - Communications which are capable of carrying a wide range of frequencies. Broadcast television, cable television, microwave, and satellite are examples of broadband technologies. A facility or circuit that has bandwidth in excess of that required for high grade voice communication.  Generally refers to transmission of data over numerous frequencies.

Broadcasting - is the distribution of audio and video signals (programs) to a number of recipients ("listeners" or "viewers") that belong to a large group. This group may be the public in general, or a relatively large audience within the public. Thus, an Internet channel may distribute text or music world-wide, while a public address system in (for example) a workplace may broadcast very limited ad hoc soundbites to a small population within its range.

Brouter - a combined bridge and router.

Bus - 1) A collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a highway on which data travels within a computer. When used in reference to personal computers, the term bus usually refers to internal bus. This is a bus that connects all the internal computer components to the CPU and main memory. There's also an expansion bus that enables expansion boards to access the CPU and memory.  All buses consist of two parts -- an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about where the data should go.  The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits of data.  Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred faster, which makes applications run faster. On PCs, the old ISA bus is being replaced by faster buses such as PCI.  Nearly all PCs made today include a local bus for data that requires especially fast transfer speeds, such as video data. The local bus is a high-speed pathway that connects directly to the processor.  2) In networking, a bus is a central cable that connects all devices on a local-area network (LAN). It is also called the backbone.

Business performance management is a software-oriented business intelligence system that some see as the new generation of business intelligence, though the terms are used interchangeably by most in the industry.

Business Process - A business process is a recipe for achieving a commercial result. Each business process has inputs, method and outputs. The inputs are a pre-requisite that must be in place before the method can be put into practice. When the method is applied to the inputs, then certain outputs will be created. A business process is a collection of related structural activities that produce something of value to the organization, its stake holders or its customers. It is, for example, the process through which an organization realizes its services to its customers. A business process can be part of a larger, encompassing process and can include other business processes that have to be included in its method. In that context a business process can be viewed at various levels of granularity. The linkage of business process with value generation leads some practitioners to view business processes as the workflows which realize an organization's use cases. A business process can be thought of as a cookbook for running a business; "Answer the phone", "place an order", "produce an invoice" might all be examples of a Business Process. A business process is usually the result of a business process design or business process reengineering activity.



CA - Conditional Access is a technology used to control access to digital television (DTV) services to authorized users by encrypting the transmitted programming. CA has been used for years for pay-TV services.

CAP - CAMEL Application Part is based on Intelligent Network (IN) capability sets with enhancements specific to mobile domain. This unique feature enables the implementation of the Virtual Home Environment (VHE) for a mobile subscriber. The CAMEL Application Part (CAP) stack provides service control for voice & data services and IP multimedia sessions. 3GPP TS 29.078 specification.

CAMEL - Customized Applications for Mobile networks Enhanced Logic is a set of GSM standards designed to work on a GSM core network. They allow an operator to define services over and above standard GSM services. The CAMEL architecture is based on the Intelligent Network (IN) standards, and uses the CAP protocol. Many services can be created using CAMEL, and it is particularly effective in allowing these services to be offered when a subscriber is roaming, like for instance no-prefix dialing (the number the user dials is the same no matter the country where the call is placed) or seamless MMS message access from abroad.

Carrier Wave - is a waveform (usually sinusoidal) that is modulated (modified) to represent the information to be transmitted. This carrier wave is usually of much higher frequency than the modulating signal (the signal which contains the information).  The reason for this is that it is much easier to transmit a signal of higher frequency, and the signal will travel further.  Carrier waves are used when transmitting radio signals to a radio receiver. Frequency modulation (FM) and amplitude modulation (AM) signals are both transmitted with the help of carrier frequencies. The frequency for a given radio station is actually the carrier wave's center frequency.  In telecommunication, the term carrier (cxr) or carrier wave has the following meanings: a waveform suitable for modulation by an information-bearing signal, an un-modulated emission. Note: The carrier is usually a sinusoidal wave or a uniform or predictable series of pulses. Synonym: carrier wave, sometimes employed as a synonym for a carrier system, or a synonym for a telecommunications provider company (operator), such as a common carrier

CDMA - Code Division Multiple Access is a spread-spectrum technology that spreads multiple conversations across a wide segment of the spectrum as opposed to splitting a channel into time slots. With CDMA, unique digital codes are used to differentiate subscribers that are simultaneously using the same spectrum. As a multiplexing scheme, CDMA is any use of any form of spread spectrum by multiple transmitters to send to the same receiver on the same frequency channel at the same time without harmful interference. Other widely used multiple access techniques are Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA). In these three schemes, receivers discriminate among various signals by the use of different codes, time slots and frequency channels, respectively.

CdmaOne - The original CDMA as first deployed by Qualcomm is the technology that is in use today in all CDMA networks that have not been upgraded to cdma2000. CdmaOne is 10–12 times more efficient than analog and 4–5 times more efficient than GSM. CDMA makes use of 1.25-MHz radio channels. In U.S. cellular systems, 30-KHz channels are aggregated to provide 1.25-MHz channels.

Cdma2000 1x - Cdma2000 1x, the next generation of CDMA, supports between 1.5 and 2 times the number of voice channels as a standard CDMA system as well as 144-Kbps packet-data services. Cdma2000 1x is 21 times more efficient than analog cellular and 4 times more efficient than TDMA networks. (Cdma2000 1x data speeds will increase from 144 Kbps to 288 Kbps by the end of 2002.)

Cdma2000 1x EV-DO - This is the next EVolution of cdma2000. “DO” indicates Data-Only and this system is capable of data speeds of up to 2.4 Mbps. This upgrade to cdma2000 requires a second 1.25-MHz channel that is used exclusively for data. Most cdma2000 network operators are expected to combine 1x and 1x EV-DO channels in their systems to provide varying voice and data capacities as required by customer demand.

Cdma2999 1x EV-DV - Motorola has been leading the standards effort. The technology is being specified to provide data-rate speeds of 1.2 Mbps for mobile users, with peak data speeds up to 5.2 Mbps for stationary users. This standard will also support voice in addition to data.

Cdma2000 3x - The 3x designation was created because some countries specify that new 3G technologies must use at least 5 MHz of spectrum. Cdma2000 3x combines 3 cdma2000 1x carriers to be used within 5 MHz of wireless spectrum.

CDPD - Cellular Digital Packet Data (CDPD) is an add-on technology that enables first-generation analog systems to provide packet data. CDPD is an IP network that runs at 19.2 Kbps with throughputs typically less than 10 Kbps. CDPD has been implemented in the U.S. by AT&T Wireless and Verizon Wireless.

Channel - Channel, in communications (sometimes called communications channel), refers to the medium through which information is transmitted from a sender (or transmitter) to a receiver. In practice, this can mean many different methods of facilitating communication, including: A connection between initiating and terminating nodes of a circuit, a single path provided by a transmission medium via either physical separation, such as by multipair cable or electrical separation, such as by frequency- or time-division multiplexing,  A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths, the portion of a storage medium, such as a track or a band, that is accessible to a given reading or writing station or head, in a communications system, the part that connects a data source to a data sink, a specific radio frequency or band of frequencies, usually in conjunction with a predetermined letter, number, or codeword, and allocated by international agreement. For example 802.11b consists of unlicensed channels 1-13 from 2412MHz to 2484MHz in 5MHz steps, in particular, a television channel. Examples include North American TV Channel 2 = 55.25MHz, Channel 13 = 211.25MHz, a room in the Internet Relay Chat (IRC) network, in which participants can communicate with each other.  In wireless terminology, a channel is the amount of wireless spectrum occupied by a specific technology implementation. For cellular, there is a transmit side and a receive side. For example, a 5-MHz channel uses 5 MHz to transmit and 5 MHz to receive for a total of 10 MHz of wireless spectrum.

Channel Blanking - This feature allows the video to be programmed blank to a black background allowing music or other audio content to be assigned to that channel.

Channel Captioning & Channel Guide - Allows labeling of channel identification information and with the press of a button, displays that information onscreen in a directory format.

CIDR - Classless Inter-Domain Routing (CIDR, pronounced "cider" or "cedar"), introduced starting in 1993, is the latest refinement to the way IP addresses are interpreted. It replaced the previous generation of IP address syntax, classful networks. It allowed increased flexibility when dividing ranges of IP addresses into separate networks. It thereby promoted: 1-) More efficient use of increasingly scarce IPv4 addresses.  2-) Greater use of hierarchy in address assignments (prefix aggregation), lowering the overhead of the Internet-wide routing. CIDR is principally a bitwise, prefix-based standard for the interpretation of IP addresses. It facilitates routing by allowing blocks of addresses to be grouped together into single routing table entries. These groups, commonly called CIDR blocks, share an initial sequence of bits in the binary representation of their IP addresses. An IP address is part of a CIDR block, and is said to match the CIDR prefix if the initial N bits of the address and the CIDR prefix are the same.  For example A.B.C.D/N: the number following the slash is the prefix length, the number of shared initial bits, counting from the left-hand side of the address.  With IPv6 addresses, the prefix length can range from 0 to 128. The prefix is written as an IPv6 address, followed by a slash and the number of significant bits.

CIF - A video format that supports both NTSC and PAL signals. CIF is part of the ITU H.261 videoconferencing standard. It specifies a data rate of 30 frames per second (fps), with each frame containing 288 lines and 352 pixels per line.

CLI - Command Line Interface.  CLI operating systems are being replaced, in most applications, by the GUI operating system (e.g. Microsoft Windows).

Clone Programming - With Clone Programming capability, you can program one television, download all the information into the Philips Clone Programming Box, and upload it into all the other units. This ensures total uniformity from set to set and saves a tremendous amount of time.

CODEC - Stands for CODer/DECoder (a telecommunications term) or COmpressing/DECompressing (a computer term). A telecom codec converts analog voice signal to digital form and vise versa.  In the computer world, a codec is used in digital video and stereo audio.

CODEC Conversion - back-to-back transfer of an analog signal from one CODEC into another CODEC in order to convert from one proprietary coding scheme (e.g. used by CLI) to another (e.g. used by PictureTel, VTel, etc.).

COFDM - Coded Orthogonal Frequency Division Multiplexing.  COFDM also sometimes called discrete multitone modulation (DMT), is a modulation scheme that divides a single digital signal across 1,000 or more signal carriers simultaneously. The signals are sent at right angles to each other (hence, orthogonal) so they do not interfere with each other. COFDM is used predominately in Europe and is supported by the Digital Video Broadcasting (DVB) set of standards. In the U.S., the Advanced Television Standards Committee (ATSC) has chosen 8-VSB (8-level Vestigial Sideband) as its equivalent modulation standard.

Comb Filter - Provides a better method of isolating luminance and chrominance thereby producing better picture quality.

Composite Video Input - A typical phono jack makes the attachment of any VCR, camcorder, Web browsers, or video game console, quick and easy for excellent picture presentation.

Composite Video Loop-Through Input/Output - A typical phono jack makes the attachment of any VCR, camcorder, Laser Disc player, Web browser, or video game console, quick and easy for excellent picture presentation.

Configuration Management - In IT and telecommunications, the term configuration management or configuration control has the following meanings:

  1. The management of security features and assurances through control of changes made to hardware, software, firmware, documentation, test, test fixtures and test documentation of an automated information system, throughout the development and operational life of a system. Source Code Management or revision control is part of this.
  2. The control of changes--including the recording thereof--that are made to the hardware, software, firmware, and documentation throughout the system lifecycle.
  3. The control and adaptation of the evolution of complex systems. It is the discipline of keeping evolving software products under control, and thus contributes to satisfying quality and delay constraints. Software configuration management (or SCM) can be divided into two areas. The first (and older) area of SCM concerns the storage of the entities produced during the software development project, sometimes referred to as component repository management. The second area concerns the activities performed for the production and/or change of these entities; the term engineering support is often used to refer this second area.
  4. After establishing a configuration, such as that of a telecommunications or computer system, the evaluating and approving changes to the configuration and to the interrelationships among system components.
  5. In distributed-queue dual-bus (DQDB) networks, the function that ensures the resources of all nodes of a DQDB network are configured into a correct dual-bus topology. The functions that are managed include the head of bus, external timing source, and default slot generator functions.

CORBA - In computing, Common Object Request Broker Architecture (CORBA) is a standard for software componentry, created and controlled by the Object Management Group (OMG). It defines APIs, communication protocol, and object/service information models to enable heterogeneous applications written in various languages running on various platforms to interoperate. CORBA therefore provides platform and location transparency for sharing well-defined objects across a distributed computing platform.  In a general sense CORBA “wraps” code written in some language into a bundle containing additional information on the capabilities of the code inside, and how to call it. The resulting wrapped objects can then be called from other programs (or CORBA objects) over the network. In this sense, CORBA can be considered as a machine-readable documentation format, similar to a header file but with considerably more information.  CORBA uses an interface definition language (IDL) to specify the interfaces that objects will present to the world. CORBA then specifies a “mapping” from IDL to a specific implementation language like C++ or Java. This mapping precisely describes how the CORBA data types are to be used in both client and server implementations. Standard mappings exist for Ada, C, C++, Lisp, Smalltalk, Java, and Python. There are also non-standard mappings for Perl and Tcl implemented by ORBs written for those languages.  The CORBA IDL is only one example of an IDL.

COTS - commercial off-the-shelf, an adjective that describes software or hardware products that are ready-made and available for sale to the general public. For example, Microsoft Office is a COTS product that is a packaged software solution for businesses. COTS products are designed to be implemented easily into existing systems without the need for customization.

Chrominance - color.

Critical Chain -  Critical Chain Project Management (CCPM) is based on methods and algorithms developed in 1997 by Eliyahu M. Goldratt. Application of CCPM has been credited with achieving projects 10% to 50% faster and/or cheaper than the traditional methods (i.e. CPM, PERT, Gantt, etc.) developed from 1910 to 1950's.  The critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are always available in unlimited quantities, then a project's critical chain is identical to its critical path.  Critical Chain uses Buffer Management as to EVM.  The main features that distinguish the critical chain from the critical path are:  1-) The use of (often implicit) resource dependencies. Implicit means that they are not included in the project network but have to be identified by looking at the resource requirements. 2-) Lack of search for an optimum solution. This means that a "good enough" solution is enough because: A-)As far as is known, there is no analytical method of finding an absolute optimum (i.e. having the overall shortest critical chain).  B-) The inherent uncertainty in estimates is much greater than the difference between the optimum and near-optimum ("good enough" solutions).  3-) The identification and insertion of buffers: A-) project buffer, B-) feeding buffers, and C-) resource buffers.

Critical Path - In project management, a critical path is the sequence of project network terminal elements with the longest overall duration, determining the shortest time to complete the project. The duration of the critical path determines the duration of the entire project. Any delay of a terminal element on the critical path directly impacts the planned project completion date (i.e. there is no float on the critical path). A project can have several, parallel critical paths. An additional parallel path through the network with the total durations just shorter than the critical path is called a sub-critical path. Originally, the critical path method considered only logical dependencies among terminal elements. A related concept is the critical chain, which adds resource dependencies. The critical path method (CPM) was invented by the DuPont corporation during the 1950's.

CRM - Customer Relationship Management. CRM entails all aspects of interaction a company has with its customer.  CRM is a process that will help bring together lots of pieces of information about customers, sales, marketing effectiveness, responsiveness and market trends.  Computerization has changed the way companies are approaching their CRM strategies because it has also changed consumer buying behavior. With each new advance in technology, especially the proliferation of self-service channels like the Web and WAP phones, more of the relationship is being managed electronically. Organizations are therefore looking for ways to personalize online experiences (a process also referred to as mass customization) through tools such as help-desk software, e-mail organizers and Web development apps.  The term CRM is used to describe either the software or the whole business strategy (or lack of one) oriented on customer needs. The second one is the description which is correct. The main misconception of CRM is that it is only software, instead of whole business strategy.  Major areas of CRM focus on service automated processes, personal information gathering and processing, and self-service. It attempts to integrate and automate the various customer serving processes within a company.



Data Modeling - In computer science, data modeling is the process of structuring and organizing data, typically using a database management system.  Managing large quantities of structured and unstructured data is a primary function of information systems. Data models describe structured data for storage in data management systems such as relational databases. They typically do not describe unstructured data, such as word processing documents, email messages, pictures, digital audio, and video. Early phases of many software development projects emphasize the design of a conceptual data model. Such a design can be detailed into a logical data model. In later stages, this model may be translated into physical data model.  The term data model actually refers to two very different things: a description of data structure and the way data are organized using, for example, a database management system.  A data model describes the structure of the data within a given domain and, by implication, the underlying structure of that domain itself. A data model may thus represent classes of entities about which a company wishes to hold information, the attributes of that information, and relationships among those entities. The model describes the organization irrespective of how data might be represented in a computer system.  Another kind of data model describes how to organize data using a database management system or other data management technology. It describes, for example, relational tables and columns or object-oriented classes and attributes. Such a data model is sometimes referred to as the physical data model, but in the original ANSI three schema architecture, it is called "logical".

DCE - Data Communications Equipment.  Also known as DCTE (Data Circuit Termination Equipment).  Data communications Equipment are installed between a DTE and the transmission circuit. Examples include LAN Network Interface Card (NIC), CSU/DSC, modem, and ISDN Terminal Adapter (TA).

DCT - Discrete Cosine Transform.  A Compression algorithm used in most of the current image compression systems for bit rate reduction, including the ITU-T P*64 recommendations for video conferencing (where P is an integer number meant to represent multiples of 64kbit/sec).  DCT represents a discrete signal or image as a sum of sinusoidal wave forms.

DHCP - In the context of computer networking, Dynamic Host Configuration Protocol (DHCP, currently implemented as DHCPv6) is a client-server networking protocol. A DHCP server provides configuration parameters specific to the DHCP client host requesting, generally, information required by the client host to participate on an IP network. DHCP also provides a mechanism for allocation of IP addresses to client hosts. DHCP emerged as a standard protocol in October 1993. RFC 2131 provides the latest (March 1997) DHCP definition. DHCP functionally became a successor to the older BOOTP protocol. Due to the backward-compatibility of DHCP, very few networks continue to use pure BOOTP. The latest standard of the protocol, describing DHCPv6 (DHCP in a IPv6 environment), appeared in July 2003 as RFC 3315.

DIAMETER - Diameter is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. The basic concept is to provide a base protocol that can be extended in order to provide AAA services to new access technologies. Diameter is intended to work in both local and roaming AAA situations. The name "DIAMETER" is a pun on the RADIUS protocol, which is the predecessor (a diameter is twice the radius). Diameter is not directly backwards compatible, but provides an upgrade path for RADIUS. The main differences are :

bullet it uses reliable transport protocols (TCP or SCTP, not UDP)
bullet it uses transport level security (IPSEC or TLS)
bullet it has transition support for RADIUS
bullet it has larger address space for AVPs (Attribute Value Pairs) and identifiers (32-bit instead of 8-bit)
bullet it is a peer-to-peer protocol, not client-server : supports server-initiated messages
bullet both stateful and stateless models can be used
bullet it has dynamic discovery of peers (using DNS SRV and NAPTR)
bullet it has capability negotiation
bullet it supports application layer acknowledgements, defines failover methods and state machines (RFC 3539)
bullet it has error notification
bullet it has better roaming support
bullet it is easier extended, new commands and attributes can be defined
bullet basic support for user-sessions and accounting is built in

DID - Direct Inward Dialing (DID) refers to a Private Branch Exchange (PBX) or CENTREX feature that allows stations to be dialed directly without the aid of an attendant.  Also, DID routing with ISDN Direct Dial, Fax and modem Servers.  Similar to Multiple Subscriber Numbering (MSN), with 10 or more subscriber numbers (as requested by the user).  Typically, DID lines are for incoming calls only.

Decoder - A piece of hardware or software that is used to convert video or audio (typically) from the digital form used in transmission or storage into a form that can be viewed.

Digital audio - Audio that has been encoded in a digital form for processing, storage or transmission.

Dithering - Giving the illusion of new color and shades by combining dots in various patterns. This is a common way of gaining gray scales and is commonly used in newspapers. The effects of dithering would not be optimal in the video produced during a videoconference.

Digital Comb Filter - Provides maximum picture quality for high resolution sources such as computers, DVD players, and laser disc.

Digital TV Ready - With the addition of a Digital TV Card the television will be compatible with ATSC compliant Digital Television signal.

Display Multiple Formats - TVs that are compatible with a wide array of PC and Mac¨ computers as well as cable or network television programming, videotapes, laser discs or practically any video format.

Distribution Amplifier (DA) - A device that allows connection of one input source to multiple output sources such as monitors or projectors.

DNIS - Digital Number Identification Service is a telco-provided digital service that delivers the called-number (the number that is dialed).

DOD - Direct Outward Dialing allows outward calls from a Private Branch Exchange (PBX) that are originated by PBX stations without assistance.

DoS - A denial-of-service attack is an attack on a computer system or network that causes a loss of service to users, typically the loss of network connectivity and services by consuming the bandwidth of the victim network or overloading the computational resources of the victim system.  A DoS attack can be perpetrated in a number of ways. There are three basic types of attack: 1-) consumption of computational resources, such as bandwidth, disk space, or CPU time. 2-)disruption of configuration information, such as routing information, 3-) disruption of physical network components.

DSL - Short for Digital Subscriber Line.  Refers collectively to all types of digital subscriber lines, the two main categories being ADSL and SDSL. Two other types of xDSL technologies are High-data-rate DSL (HDSL) and Very high DSL (VDSL). DSL technologies use sophisticated modulation schemes to pack data onto copper wires. They are sometimes referred to as last-mile technologies because they are used only for connections from a telephone switching station to a home or office, not between switching stations.  xDSL is similar to ISDN inasmuch as both operate over existing copper telephone lines (POTS) and both require the short runs to a central telephone office (usually less than 20,000 feet). However, xDSL offers much higher speeds - up to 32 Mbps for upstream traffic, and from 32 Kbps to over 1 Mbps for downstream traffic.

DSLAM - Short for Digital Subscriber Line Access Multiplexer, a mechanism at a phone company's central location that links many customer DSL connections to a single high-speed ATM line.  When the phone company receives a DSL signal, an xDSL modem with a POTS splitter detects voice calls and data. Voice calls are sent to the PSTN, and data are sent to the DSLAM, where it passes through the ATM to the Internet, then back through the DSLAM and xDSL modem before returning to the customer's PC.  More DSLAMs a phone company has, the more customers it can support.

DTE - Data Terminal Equipment.  A term used in the data world to indicate a terminal device.  DTE is part of a broader grouping of equipment known as CPE (Customer Premises Equipment), which includes voice, as well as data, terminals.  DTE can be a dumb terminal or a server computer.  DTE interfaces to a circuit through DCE.

DTV - Digital television is the transmission of television signals using digital rather than conventional analog methods. Conventional standards - National Television Standards Committee (NTSC), Phase Alternation Line (PAL), and Sequential Couleur avec Memoire (SECAM) - specify analog transmission. However, both the audio and video components of a television signal can be transmitted in digital form. The advantages of DTV over analog TV include: Superior image resolution (detail) for a given bandwidth, smaller bandwidth for a given image resolution, compatibility with computers and the Internet, interactivity, superior audio quality, consistency of reception over varying distances.

Due diligence is the effort a party makes to avoid harm to another party. Failure to make this effort is considered negligence. Quite often a contract will specify that a party is obligated to provide due diligence.

DVB - Digital Video Broadcasting. DVB is a set of standards that define digital broadcasting using existing satellite, cable, and terrestrial infrastructures.  A fundamental decision of the DVB Project was the selection of MPEG-2, one of a series of MPEG standards for compression of audio and video signals.



E.164 - ITU Recommendation for international telecommunications numbering.  mainly for ISDN/B-ISDN/SMDS.  In short a scheme to assign numbers to phone lines.

E Channel - E stands for echo.  It is the 16Kbps ISDN basic rate channel echoing contents of DCEs to DTEs.  Used in binding for access to multipoint link.

EAI - Enterprise Application Integration is defined as the use of software and computer systems architectural principles to integrate a set of enterprise computer applications.  EAI has increased in importance because enterprise computing often takes the form of islands of automation. This occurs when the value of individual systems are not maximized due to partial or full isolation. If integration is applied without following a structured EAI approach, point-to-point connections grow across an organization. Dependencies are added on an impromptu basis, resulting in a tangled mess that is difficult to maintain. This is commonly referred to as spaghetti, an allusion to the programming equivalent of spaghetti code. The equation for n-connections is: n(n-1)/2. EAI is not just about sharing data between applications; it focuses on sharing both business data and business process. Attending to EAI involves looking at the system of systems, which involves large scale inter-disciplinary problems with multiple, heterogeneous, distributed systems that are embedded in networks at multiple levels.  EAI uses an Enterprise service bus (ESB), which connects numerous, independent systems together. Although other approaches have been explored, including connecting at the database or user-interface level, the ESB approach has been adopted as the strategic winner. Individual applications can publish messages to the bus and subscribe to receive certain messages from the bus. Each application only requires one connection to the bus. The message bus approach can be extremely scalable and highly evolvable.  EAI is related to middleware technologies such as message-oriented middleware (MOM), and data representation technologies such as XML. Newer EAI technologies involve using web services as part of service-oriented architecture as a means of integration. EAI tends to be data centric; however, it will come to include content integration and business processes.

Enterprise JavaBeans - The Enterprise JavaBeans (EJB) specification is one of the several Java APIs in the Java Platform, Enterprise Edition. EJB is a server-side component that encapsulates the business logic of an application. The EJB specification was originally developed by Sun Microsystems (EJB 1.0 and 1.1) and later under the Java Community Process as JSR 19 (EJB 2.0), JSR 153 (EJB 2.1) and JSR 220 (EJB 3.0). The EJB specification details how an application server provides:

bullettransaction processing
bulletconcurrency control
bulletevents using Java Message Service
bulletnaming and directory services (JNDI)
bulletsecurity ( JCE and JAAS )
bulletdeployment of software components in an application server
bulletremote procedure calls (RPC) using RMI-IIOP or CORBA
Additionally, the Enterprise JavaBean specification defines the roles played by the EJB container and the EJBs as well as how to deploy the EJBs in a container.
EJBs are deployed in an EJB container within the application server. The specification describes how an EJB interacts with its container and how client code interacts with the container/EJB combination. The EJB classes used by applications are included in the
javax.ejb package. (The javax.ejb.spi package is a service provider interface used only by EJB container implementations.).  Each EJB must provide a Java implementation class and two Java interfaces. The EJB container will create instances of the Java implementation class to provide the EJB implementation. The Java interfaces are used by client code of the EJB.  The two interfaces, referred to as the Home and the Component interface, specify the signatures of the EJB's remote methods. The methods are split into two groups (Note: Additionally Home or the Component Interfaces can be Local or Remote):
bulletmethods that are not tied to a specific instance, such as those used to create an EJB instance or to find an existing entity EJB (see EJB Types, below). These are declared by the Home interface.
bulletmethods that are tied to a specific instance. These are placed in the Remote interface.
Because these are merely Java interfaces and not concrete classes, the EJB container must generate classes for these interfaces that will act as a proxy in the client. Client code invokes a method on the generated proxies, which in turn places the method arguments into a message and sends the message to the EJB server. The proxies == use RMI-IIOP to communicate with the EJB server.  The server will invoke a corresponding method on an instance of the Java implementation class to handle the remote method invocation.

Erlang Distribution - The Erlang distribution is a continuous probability distribution with wide applicability primarily due to its relation to the exponential and Gamma distributions. The Erlang distribution was developed by A. K. Erlang to examine the number of telephone calls which might be made at the same time to the operators of the switching stations. This work on telephone traffic engineering has been expanded to consider waiting times in queuing systems in general. The distribution is now used in the field of stochastic processes. 

Easy A/V Switching - Provides immediate access to A/V inputs via the TV's front panel or remote control.

EDGE - Enhanced Data Rates for Global Evolution is a technology being promoted by the TDMA and GSM communities that is capable of both voice and 3G data rates. EDGE is being considered by AT&T Wireless and Cingular Wireless as a 3G solution. EDGE is still in the lab and field trials have not confirmed its capabilities.

EDM - Enterprise Data Management is an enterprise wide PLM/ PDM data management system that facilitates the communication of product data through the whole organization (not just in the engineering department) as well as links to other corporate systems such as ERM CRM SCM.  EDM entails all aspects of managing automated decision design and deployment that an organization uses to manage its interactions with customers, employees and suppliers. Computerization has changed the way organizations are approaching their decision-making because it has enabled information-based decisions: decisions based on analysis of historical behavioral data, decisions and their outcomes. Organizations seek to improve their Decision Yield (the value created through each decision) by deploying business processes and software solutions that better manage the tradeoffs between precision, consistency, agility, speed, and cost of decision-making within organizations.

EFR - Enhanced Full Rate or GSM-EFR is a speech coding standard that was developed in order to improve the quite poor quality of GSM-Full Rate (FR) codec. Working at 12.2 kbit/s the EFR provides wire like quality in any noise free and background noise conditions. The EFR 12.2 kbit/s speech coding standard is compatible with the highest AMR mode.

EGP - Exterior Gateway Protocol is a routing protocol for the Internet originally specified in 1982 by Eric C. Rosen of Bolt, Beranek, and Newman, and David L. Mills. It was first described in RFC 827 and formally specified in RFC 904 (1984). EGP is a type of path vector protocol.  During the early days of the Internet, an exterior gateway protocol, EGP version 3, was used to interconnect autonomous systems. EGP3 should not be confused with EGPs in general. Currently, BGP is the accepted standard for Internet routing and has essentially replaced the more limited EGP3.

EIGRP - Enhanced Interior Gateway Routing Protocol is a Cisco proprietary routing protocol based on their original IGRP. EIGRP is a balanced hybrid IP routing protocol, with optimizations to minimize both the routing instability incurred after topology changes, as well as the use of bandwidth and processing power in the router.  Some of the routing optimizations are based on the Diffusing Update Algorithm (DUAL) work from SRI, which guarantees loop-free operation. In particular, DUAL avoids the "count to infinity" behavior of RIP when a destination becomes completely unreachable. The maximum hop count of EIGRP-routed packets is 224.  The data EIGRP collects is stored in three tables: 1- Neighbor Table, 2-Topology Table (or Feasible successor table), 3- Routing table.  EIGRP associates five different metrics with each route: Delay, Bandwidth, Reliability, Load, MTU (though not actually used in the calculation).

EIR - The Equipment Identity Register is often integrated to the HLR. The EIR keeps a list of mobile phones (identified by their IMEI) which are to be banned from the network or monitored. This is designed to allow tracking of stolen mobile phones. In theory all data about all stolen mobile phones should be distributed to all EIRs in the world through a Central EIR. It is clear, however, that there are some countries where this is not in operation. The EIR data does not have to change in real time, which means that this function can be less distributed than the function of the HLR.

Embedded Systems - An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. As opposed to a general-purpose computer, such as a personal computer, an embedded system performs pre-defined tasks, usually with very specific requirements. In an application where the system is dedicated to a specific task, design engineers are able to optimize the system extensively, thus considerably reducing the size and cost of the end product. Due to the low-cost advantage, embedded systems are commonly built into products designed for mass production.  The core of any embedded system is a microprocessor or a microcontroller, which is programmed to perform a small number of tasks. In contrast to a general purpose computer which at any time can run essentially any software application the user chooses, the software on an embedded system is semi-permanent; so it is often called "firmware".

EMS - An Enterprise Messaging System is a set of published Enterprise-wide standards that allows organizations to send semantically precise messages between computer systems. EMS systems promote loosely coupled architectures that allow changes in the formats of messages to have minimum impact on message subscribers. EMS systems are facilitated by the use of XML messaging, SOAP and Web services. EMS usually take into account the following considerations:1-) Security Messages must be encrypted if they travel over a public interfaces. Messages must be authenticated or digitally signed if the receiver is to have confidence the messages have not been tampered in transit. 2-) Routing Messages need to be routed efficiently from the sender to the receiver. Intermediate nodes may need to route the messages if the body of the message is encrypted. 3-) Metadata The body of the document contains information that must be unambiguously interpreted. Metadata registries should be used to create precise definitions for each data element. 4-) Subscription Systems should be able to subscribe to all messages that match a specific pattern. Messages with a specific content may be routed differently. For example some messages may have different priority or security policies. 5-) Policy Enterprise messaging systems should provide some consideration for a centralized policy of messages such as what classes or roles of users can access different fields of any message.

ENG - Electronic News Gathering.

EnterpriseNet - Suites of integrated, intranet/extranet applications that enable users outside a firewall to share, manipulate and interact with data inside the firewall. The suites can include Help Desk, Contact, Defect Tracking System, Collaborative Workspace and Data Publisher.

ENUM - Telephone Number Mapping (ENUM or Enum, from TElephone NUmber Mapping) is a suite of protocols to unify the telephone system with the Internet by using E.164 addresses with DDDS and DNS. ENUM also refers to "E164 NUmber Mapping". Although it facilitates VoIP, the protocol used for voice communication across the Internet, ENUM is not a VoIP requirement and should not be confused with common VoIP routing based on SIP and H.323 protocols with a Uniform Resource Identifier (URI). VoIP service providers assign a URI to a customer in order to complete calls over the internet. ENUM is a DNS-based protocol that is best suited to offer services that not only help facilitate, but expand on ways to complete calls over VoIP networks as described below. It provides a user with a domain name on an E.164 server in order to associate a common international telephone number with a URI and provide other DNS-related services. The server is maintained by the Service Provider and is expected to become standard since it can successfully address locating URIs with nothing more than a common international telephone number. The ITU ENUM allocates a specific zone, namely "e164.arpa" for use with E.164 numbers. Any phone number, such as +1 555 42 42 can be transformed into a hostname by reversing the numbers, separating them with dots and adding the e164.arpa suffix thus:
DNS can then be used to look up Internet addresses for services such as SIP VoIP telephony. NAPTR records are used to 'translate' E.164 addresses to SIP addresses for example. An example NAPTR record is:
IN NAPTR 100 10 "u" "sip+E2U" "!^.*$!sip:phoneme@example.net!"
IN NAPTR 102 10 "u" "mailto+E2U" "!^.*$!mailto:myemail@example.com!"
This example specifies that if you want to use the "sip+E2U" service, you should use sip:phoneme@example.net as the address. The regular expression can be used by a telephone company to easily assign addresses to all of its clients. For example, if your number is +15554242, your SIP address is sip:4242@555telco.example.net; if your number is +15551234, your SIP address is sip:1234@555telco.example.net.
Alternative ENUM lookup protocols such as sbXML have also emerged. These services often provide a faster and easier mechanism to translate E.164 numbers into SIP addresses. ITU e164.arpa subdomains are first delegated to ("registered by") regulatory bodies designated by the national government of the country code concerned, which further delegates zones to telecommunications providers. Your telephone company is therefore in charge of the NAPTR records, usually. Some countries are proposing to let end-users register their own telephone numbers via an intermediary, which need not be their own telco. This is considered a good idea as VoIP is a major Enum use. People who use an Enum-enabled VoIP service can dial your existing number and be connected not to your existing phone line, but to your own VoIP telephone directly via the Internet, bypassing the telephone system entirely. When they call someone who does not use Enum, calls complete over the Public Switched Telephone Network or PSTN. Alternative free public ENUM services such as E164.org have also emerged. These services often verify PSTN numbers and can be used in addition to e164.arpa. Competing ENUM zones may be seen as beneficial, to keep prices low in the VoIP market.

EoIP - Everything over IP.  IP enabled services like Data, Voice, video, and TV, etc.

Ephemeral - used in describing H.248 terminations representing RTP flow i.e. ephemeral or created per call.

Erlang - An Erlang is a unit of telephone voice use that specifies the total capacity or average use of a telephone system. One Erlang is equivalent to the continuous usage of a telephone line.

ERM - Enterprise Relationship Management is software that analyzes data it has about its customers to develop a better understanding of the customer and how the customer is using its products and services. This kind of application may use data mining of its data warehouse or existing sales, marketing, service, finance, and manufacturing databases to generate new information about its customer relationships.

ERP - Enterprise Resource Planning.  a business management system that integrates all facets of the business, including planning, manufacturing, sales, and marketing. As the ERP methodology has become more popular, software applications have emerged to help business managers implement ERP in business activities such as inventory control, order tracking, customer service, finance and human resources.

ESB - an Enterprise Service Bus refers to a software architecture construct, implemented by technologies found in a category of middleware infrastructure products usually based on Web services standards, that provides foundational services for more complex service-oriented architectures via an event-driven and XML-based messaging engine (the bus). An ESB generally provides an abstraction layer on top of an Enterprise Messaging System (EMS) which allows integration architects to exploit the value of messaging without writing code. Contrary to commonly used EAI brokers which are usually implemented as a monolithic stack in a hub and spoke architecture, the foundation of an ESB is built of base functions broken up into their constituent parts, with distributed deployment where needed, working in harmony as necessary.  Microsoft DotNET Platform Microsoft BizTalk Server is an example vendor of ESB.

ESPTM (Energy Saving Programmability) - Energy Saving system that powers television off after a specified period of use. A simple countdown clock can be selectively set to operate from 0-99 hours with automatic clock reset at each power up.

ETL - Extract, Transform, and Load: extracting data from outside sources, transforming it to fit business needs, and ultimately loading it into the data warehouse.   ETL is important, as it is the way data actually gets loaded into the warehouse.  ETL is a BI term.

Event Programming - This feature allows the television to turn on automatically, tune to a specific channel or source at a specific time, and turn itself off. (e.g. up to five events a day can be pre-programmed).

Event Scheduling - Schedule a television, group of televisions or the entire network of televisions for a specific event including power on, channel selection, and volume control.

EVM -  Earned Value Management is an integrated program management technique that integrates technical performance requirements, resource planning, with schedules, while taking risk into consideration. The major objectives of applying earned value to a contract are to encourage contractors to use effective internal technical, cost and schedule management control systems, and to permit the customer to rely on timely data produced by those systems for better management insight. This data is in turn used for determining product-oriented contract status, and projecting future performance based on trends of date.  In addition, Earned Value Management allows better and more effective management decision making to minimize adverse impacts to the project.   In other words, Earned value is a management technique that relates resource planning to schedules and to technical cost and schedule requirements. All work is planned, budgeted, and scheduled in time-phased ''planned value'' increments constituting a cost and schedule measurement baseline. There are two major objectives of an earned value system: to encourage contractors to use effective internal cost and schedule management control systems; and to permit the customer to be able to rely on timely data produced by those systems for determining product-oriented contract status.  Earned Value Management provides an objective measurement of how much work has been accomplished on a project. Using the earned value process, the management team can readily compare how much work has actually been completed against the amount of work planned to be accomplished. All work is planned, budgeted, and scheduled in time-phased "planned value" increments constituting a Performance Measurement Baseline. 

- Budgeted Cost of Work Scheduled (BCWS) or Planned Value (PV): tasks planned to be finished for the period.

- Budgeted Cost of Work Produced (BCWP) or Earned Value (EV): for every period the budgets of the tasks that actually finished in this time unit. 'How much work is done?'

- Actual Cost (AC) of work produced (ACWP) or effort spent: actual cost of the work

- Budget At Completion (BAC): ∑BCWS (or ∑PV), the total budget estimated to be spent to complete the project

- Total Funding Available (TFA): the budget the client has committed to

- Negotiated Period Of Performance (NPOP): the time period the client has agreed upon with the project manager

- Planned Period Of Performance (PPOP): the time period thought required to finish the project

- Cost Accrual Ratio (CAR): the total average cost per person per time unit

- Forecast of remaining work (FCST) or current schedule: the work that still needs to be done after this time unit

- Estimate To Complete (ETC), the projection of remaining costs to be incurred

Cost Variation = EV - AC; if negative => project cost more than budgeted

Schedule Variance = EV - PV; if negative => project did not finish on time as scheduled

Cost Performance Index = BCWP (EV) / ACWP (AC); if <1 then the cost was higher than planned

Schedule Performance Index = BCWP (EV) / BCWS (PV); if <1 then the actual schedule not as planned

Estimate At Completion (EAC) = ACWP (AC) + ETC (Manager's projection)

To-Complete Performance Index (TCPI) = (BAC - BCWP (EV)) / ETC; is compared to CPI

Independent Estimate At Completion (IEAC) = ∑AC + ((BAC-∑EV) / CPI);

Exceptional Video Performance - monitor/receiver that delivers 680+ lines of resolution (S-Video Input), allowing hookup of high resolution sources such as S-VHS and laserdisc.

Extranet - An extranet is a private network that uses Internet technology and the public telecommunication system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses. An extranet can be viewed as part of a company's intranet that is extended to users outside the company. It has also been described as a "state of mind" in which the Internet is perceived as a way to do business with other companies as well as to sell products to customers.  An extranet requires security and privacy. These can include firewalls server management, the issuance and use of digital certificates or similar means of user authentication, encryption of messages, and the use of virtual private networks (VPNs) that tunnel through the public network.  An extranet could be described as two or more intranets with network connectivity. Generally, and as with intranets, an extranet will be based on Internet Protocols. The underlying network technology does not really matter, for instance it may be that organizations use the Internet for carrying data but restrict access to resources from the general public via firewalls. A virtual private network could be set up over the Internet to achieve the same result.

External Speaker Connections - Institutional Televisions and display products give users the ability to connect external speakers directly into the back of the set, eliminating the need for an external amplifier or A/V receiver.



FDDI - Abbreviation of Fiber Distributed Data Interface, a set of ANSI protocols for sending digital data over fiber optic cable. FDDI networks are token-passing networks, and support data rates of up to 100 Mbps (100 million bits) per second. FDDI networks are typically used as backbones for wide-area networks.  An extension to FDDI, called FDDI-2, supports the transmission of voice and video information as well as data. Another variation of FDDI, called FDDI Full Duplex Technology (FFDT) uses the same network infrastructure but can potentially support data rates up to 200 Mbps.

FDM - Frequency-division multiplexing is a form of signal multiplexing where multiple baseband signals are modulated on different frequency carrier waves and added together to create a composite signal. FDM can also be used to combine multiple signals before final modulation onto a carrier wave. In this case the carrier signals are referred to as subcarriers: an example is stereo FM transmission, where a 38 KHz subcarrier is used to separate the left-right difference signal from the central left-right sum channel, prior to the frequency modulation of the composite signal. Where frequency division multiplexing is used as to allow multiple users to share a physical communications channel, it is called frequency-division multiple access (FDMA). FDMA is the traditional way of separating radio signals from different transmitters. The analog of frequency division multiplexing in the optical domain is known as wavelength division multiplexing.

FDMA, or frequency-division multiple access, is the oldest and most important of the three main ways for multiple radio transmitters to share the radio spectrum. The other two methods are Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA).  In FDMA, each transmitter is assigned a distinct frequency channel so that receivers can discriminate among them by tuning to the desired channel.  TDMA and CDMA are always used in combination with FDMA, i.e., a given frequency channel may be used for either TDMA or CDMA independently of signals on other frequency channels. (Ultra wideband is arguably an exception, as it uses essentially all of the usable radio spectrum in one location.)

FEC - Forward Error Correction (algorithms).

Field - In interlaced video, it takes two scans on a screen to make a complete picture, or a Frame. Each scan is called a Field. Sometimes these are referred to as field 1 and field 2.

File Sharing - is the practice of making files available for other users to download over the Internet and smaller networks. File sharing is one of the original applications of the Internet.  Usually file sharing follows the peer-to-peer (P2P) model, where the files are stored on and served by personal computers of the users. Most people who engage in file sharing are also downloading files that other users share. Sometimes these two activities are linked together. P2P File sharing is distinct from file trading in that downloading files from a P2P network does not require uploading, although some networks either provide incentives for uploading such as credits or force the sharing of files being currently downloaded.

Firewall - In computing, a firewall is a piece of hardware and/or software which functions in a networked environment to prevent some communications forbidden by the security policy, analogous to the function of firewalls in building construction. A firewall is also called a Border Protection Device (BPD), especially in NATO contexts, or packet filter in BSD contexts. A firewall has the basic task of controlling traffic between different zones of trust. Typical zones of trust include the Internet (a zone with no trust) and an internal network (a zone with high trust). The ultimate goal is to provide controlled connectivity between zones of differing trust levels through the enforcement of a security policy and connectivity model based on the least privilege principle. Proper configuration of firewalls demands skill from the administrator. It requires considerable understanding of network protocols and of computer security. Small mistakes can render a firewall worthless as a security tool.

There are three basic types of firewalls depending on:


Whether the communication is being done between a single node and the network, or between two or more networks.


Whether the communication is intercepted at the network layer, or at the application layer.


Whether the communication state is being tracked at the firewall or not.

With regard to the scope of filtered communications there exist:


Personal firewalls, a software application which normally filters traffic entering or leaving a single computer.


Network firewalls, normally running on a dedicated network device or computer positioned on the boundary of two or more networks or DMZs (demilitarized zones). Such a firewall filters all traffic entering or leaving the connected networks.

The latter definition corresponds to the conventional, traditional meaning of "firewall" in networking. In reference to the layers where the traffic can be intercepted, three main categories of firewalls exist:


Network layer firewalls. An example would be iptables.


Application layer firewalls. An example would be TCP Wrapper.


Application firewalls. An example would be restricting ftp services through /etc/ftpaccess file

These network-layer and application-layer types of firewall may overlap, even though the personal firewall does not serve a network; indeed, single systems have implemented both together. There's also the notion of application firewalls which are sometimes used during wide area network (WAN) networking on the world-wide web and govern the system software. An extended description would place them lower than application layer firewalls, indeed at the Operating System layer, and could alternately be called operating system firewalls. Some firewalls have higher privileges than others like mysql and pj.  Lastly, depending on whether the firewalls track packet states, two additional categories of firewalls exist:


Stateful firewalls


Stateless firewalls

Network layer firewalls operate at a (relatively) low level of the TCP/IP protocol stack as IP-packet filters, not allowing packets to pass through the firewall unless they match the rules. The firewall administrator may define the rules; or default built-in rules may apply (as in some inflexible firewall systems).  A more permissive setup could allow any packet to pass the filter as long as it does not match one or more "negative-rules", or "deny rules". Today network firewalls are built into most computer operating systems and network appliances.  Modern firewalls can filter traffic based on many packet attributes like source IP address, source port, destination IP address or port, destination service like WWW or FTP. They can filter based on protocols, TTL values, netblock of originator, domain name of the source, and many other attributes.

Application-layer firewalls work on the application level of the TCP/IP stack (i.e., all browser traffic, or all telnet or ftp traffic), and may intercept all packets traveling to or from an application. They block other packets (usually dropping them without acknowledgement to the sender). In principle, application firewalls can prevent all unwanted outside traffic from reaching protected machines.  By inspecting all packets for improper content, firewalls can even prevent the spread of the likes of viruses. In practice, however, this becomes so complex and so difficult to attempt (given the variety of applications and the diversity of content each may allow in its packet traffic) that comprehensive firewall design does not generally attempt this approach.  The XML firewall exemplifies a more recent kind of application-layer firewall.

Proxies: A proxy device (running either on dedicated hardware or as software on a general-purpose machine) may act as a firewall by responding to input packets (connection requests, for example) in the manner of an application, whilst blocking other packets.  Proxies make tampering with an internal system from the external network more difficult and misuse of one internal system would not necessarily cause a security breach exploitable from outside the firewall (as long as the application proxy remains intact and properly configured). Conversely, intruders may hijack a publicly-reachable system and use it as a proxy for their own purposes; the proxy then masquerades as that system to other internal machines. While use of internal address spaces enhances security, crackers may still employ methods such as IP spoofing to attempt to pass packets to a target network.

Network address translation: Firewalls often have network address translation (NAT) functionality, and the hosts protected behind a firewall commonly use so-called "private address space", as defined in RFC 1918. Administrators often set up such scenarios in an effort (of debatable effectiveness) to disguise the internal address or network.

Management: The Middlebox Communication (midcom) Working Group of the Internet Engineering Task Force is working on standardizing protocols for managing firewalls and other middleboxes. See, e.g., Middlebox Communications (MIDCOM) Protocol Semantics.

Flexible Connectivity - A televisions feature allowing a multitude of input/output capabilities including interface slot, S-Video input/output, two audio inputs, Composite Video input/output, Smart PlugTM interface, and RF input.

Flicker Filter - Advanced filter results in improved computer-generated graphics display and higher resolution.

Float - Float in project management is the amount of time that a terminal element in a project network can be delayed by, without causing a delay to: a-) subsequent terminal elements (free float), and b-) project completion date (total float).  (float = LS - ES).

FM - Frequency modulation is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave. (Contrast this with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant.)  In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. Digital data can be represented by shifting the carrier frequency among a set of discrete values, a technique known as frequency-shift keying.  FM is commonly used at VHF radio frequencies for high-fidelity broadcasts of music and speech (see FM broadcasting). A narrowband form is used for voice communications in commercial and amateur radio settings. The type of FM modulation is generally called wide-FM, or W-FM, and in other parts of the spectrum, narrowband narrow-fm (N-FM) is used to conserve bandwidth.  It is also used to send signals into space.  FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the luminance (black and white) portion of the video signal. FM is the only feasible method of recording to and retrieving from magnetic tape without extreme distortion a signal with a very large range of frequency components -- a video signal has components from a few hertz to several megahertz.  FM is also used at audio frequencies to synthesize sound. This technique, known as FM synthesis, was popularized by early digital synthesizers and became a standard feature for several generations of personal computer sound cards.

FM radio - is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity sound over broadcast radio. FM radio is distributed primarily through broadcast reception of FM radio signals, although it is also possible to distribute FM signals via cable FM, either by using an adapter to plug analogue cable wires directly into an FM receiver, or through the use of television channel allocations on a digital cable service.

FOA - First Office Application.  A telephony term for beta testing.

FOMA - Freedom Of Mobile multimedia Access (FOMA) is the name of NTT DoCoMo’s WCDMA service. FOMA is a modified version of UMTS Release 99 with an initial data rate of 64 Kbps. It is expected that NTT DoCoMo will transition to the final release of UMTS in 2003 or later.

Frame - In interlaced video, a Frame is one complete picture in a video or film. A Frame is made up of two fields, or two sets of interlaced lines. A video frame comprises two interlace fields of  either 525 lines (NTSC) or 625 lines (PAL).  Full-motion video for NTSC runs at 30 frames per second (fps); for PAL, 25 fps.  Film runs at 24 fps.

Frequency Agile - Televisions can be controlled through RF cable TV distribution system and can be configured to communicate at a variety of frequencies so that most RF distribution systems should require minimal modifications or adjustments.

Freenet - is a decentralized censorship-resistant peer-to-peer distributed data store aiming to provide electronic freedom of speech through strong anonymity. Freenet works by pooling the contributed bandwidth and storage space of member computers to allow users to anonymously publish or retrieve various kinds of information. Freenet uses a kind of key based routing similar to a distributed hash table to locate peers' data.

Front A/V Jacks - Fast, easy connection of external video sources (VCR, camcorder, or video games.

Front Control Lockout - Provides the ability to limit or total disable the buttons found on the front of the set.

Full duplex - Sending data in both directions at the same time. Usually higher quality, but requires more bandwidth. In video conferencing, full duplex will be much more natural and useable. Cheap speakerphones are half duplex, whereas more expensive ones are full duplex.

Full Motion Video - A standard video signal that can be transmitted by a variety of means including television broadcast, microwave, fiber optics, and satellite. Full motion video traditionally requires 6 MHz in analog format and 45 Mbps when encoded digitally. Industry agreements are still needed for efficiently mapping advanced digital video streams into ATM and handling the effect of "cell jitter" in applications where video and audio synchronization is crucial. Since 1994 there have been multimedia experiments over MBONE (Multicast backBONE) primarily by NASA and the military. Some form of video compression normally is used to reduce the amount of data and to allow it to be read from disk quickly enough. The time taken for compression can be relatively long; decompression is done in real-time with the picture quality and frame rate varying with the processing power available. Two compression standards discussed with full motion video are H.261 and MPEG. H.261 was developed before 1992 to work with ISDN and support video conferencing.



G.7xx - A family of ITU standards for audio compression.

G.711 - Audio codec standard for 3 kHz audio using 48 or 56 kbps bandwidth.

G.722 - Audio codec standard for 7 kHz audio using 48 or 56 kbps bandwidth.

G.723 - Audio codec standard to be used with POTS H.324 video  codec standard.

G.728 - Newer audio codec standard for 3 kHz audio using only 16 kbps bandwidth.

GAIT - GSM ANSI-136 Interoperability Team (GAIT) is a technology that enables GSM and TDMA networks to interoperate. Special handsets must be manufactured (often called “GAIT phones”) and used in conjunction with GAIT networking. Currently there are no GAIT handsets, nor are there any GAIT networks in operation.

GAN - Gallium nitride is a semiconductor compound expected to make possible miniaturized, high-power wireless transmitters. These transmitters will be combined with sensitive receivers into telephone sets capable of directly accessing communications satellite.

Gatekeeper - In the H.323 world, the gatekeeper provides several important functions. First, it controls access to the network, allowing or denying calls and controlling the bandwidth of a call. Second, it helps with address resolution, making possible email type names for end users, and converting those into the appropriate network addresses. They also handle call tracking and billing, call signaling, and the management of gateways. They also handle call tracking and billing, call signaling, and the management of gateways.

Gateway - Gateways provide a link between the H.323 world and other video conferencing systems. A common example would be a gateway to a H.320 (ISDN) video conferencing system.

GERAN - GSM EDGE Radio Access Network. It is one of the main 3GPP (Third Generation Partnership Project) UMTS standardization areas.

GPRS - GSM Packet Radio Service or General Packet Radio Service (GPRS) is an upgrade to a GSM network that adds packet data to the voice network. GPRS uses the same time slots as voice calls and each time slot is capable of approximately 9.6 Kbps of data throughput. A GPRS network that offers 28.8 Kbps down to the phone and 9.6 Kbps from the phone back to the network is using three time slots down and one up. GPRS network operators and vendors tend to add the two speeds together when discussing data speeds. This example would be called a system with 38-Kbps data capability.

GSM - Global System for Mobility (GSM) is a TDMA digital technology deployed first in Europe. Today 65-70% of all wireless voice networks use GSM technology. GSM is less efficient than TDMA since it requires a 200-KHz channel.  GSM capacity is 3 to 4 times that of analog service.

GUI - Graphical User Interface (e.g. Microsoft Windows operating system).



H.221 - Protocol for combining audio, video and data into a frame for transport with ISDN.  Also for separating audio, video, and data from a received frame.

H.224 - ITU-T Recommendation. A real time control protocol for simplex applications using the H.221 LSD/HSD/MLP channels.

H.230 - Defines low-level system control and indication for ISDN (i.e. on frame level).

H.239 - is a standard for showing the data (content) along with the Video also known as People+content.  H.239 is not T.120 or DuoVideo as known and introduced by Tandberg.  H.239 just allows you to send and receive the content as a video source and would not allow for any collaboration.

H.242 - Defines high-level system control and indication for ISDN (i.e. on capabilities level).

H.243 - The standards for multipoint conferences with three or more stations connected over digital networks.

H.248 - H.248 was jointly developed by ITU-T SG16 and IETF Working group MEGACO.  H.248 is the standards organizations' answer to MGCP, SGCP, IPDC, etc.  ITU Recommendation has been approved 15th June 2000.  IETF has published three RFCs on Megaco: RFC 2885, RFC 2886(corrections), RFC 3015(merged).  The H.248 architecture is comprised of packages and core protocol.  Packages are used to allow different bearer types and application (e.g. fax, server, telephony, text, etc.).  Core protocol for Registration, Connection model, and Commands.

H.261 - ITU-T Recommendation.  Video coding for videoconferencing. H.261 is a discrete cosine transform (DCT) based algorithm for video in the 64kb/s to 2mb/s range. All H.323 compliant video conferencing system are required to support this codec.

H.263 - ITU-T Recommendation.  Video coding within videoconferencing. H.263 offers better compression than H.261, particularly in the low bit rate range of up to 128Kbps.

H.264 - Has received Final Draft status on March 28, 2003 by the Joint Video Team (JVT), a committee of Moving Picture Experts Group (MPEG) and International Standards Organization/International Telecommunications Union (ISO/ITU). Final ratification of H.264 by the ITU happened on May 30th. H.264 is also known as AVC (Advanced Video Coding) or MPEG-4 part 10.  H.264 was designed to enable videoconferences to connect at half the bandwidth and still retain the same quality or it will deliver twice the quality at the same bandwidth normally used.  This recently defined video encoding and decoding scheme has mixed reviews.  Vendors praise it, and users in the Labs are questioning the promised video quality improvement.  However, the majority agrees that H.264 delivers a noticeable performance improvement over  H.261 and H.263 at lower bandwidth (<192Kbps) and primarily over H.323.  It will be some time before H.264 compatibility issues between different vendors are resolved.

H.281 - ITU-T Recommendation.  Far End Camera Control (FECC).

H.320 - ITU-T Recommendation for videoconferencing over ISDN, V.35, and fractional E1/T1 lines. It includes the H.261 video codec standard, the H.221, and H.230.

H.321 - ITU-T Recommendation for the adaptation to the ATM environment of H.320 videoconferencing standards.  Also see H.320 and V.80.

H.323 - ITU-T Recommendation which serves as the "umbrella" for a set of standards defining real-time multimedia communications for packet based networks.

H.324 - ITU-T Recommendation for video conferencing over analog POTS  telephone lines. Also see V.80.

H.350 - ITU-T Recommendation describing a directory services architecture for multimedia conferencing using LDAP. Standardized directory services can support association of persons with endpoints, searchable white pages, and clickable dialling. Directory services can also assist in the configuration of endpoints, and user authentication based on authoritative data sources.  This document describes a standardized LDAP schema to represent endpoints on the network and associate those endpoints with users. It discusses design and implementation considerations for the inter-relation of video and voice-specific directories, enterprise directories, call servers and endpoints.  Also see RFC3944.

Half duplex - A telecommunications system where data can only flow in one direction at a time. Cheaper speakerphones are a good example of this, where only one person can talk at a time.

Handoff - In cellular telecommunications, the term handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another. In satellite communications it is the process of transferring satellite control responsibility from one earth station to another without loss or interruption of service. The British English term for transferring a cellular call is handover, which is the terminology standardized within such European originated technologies as GSM and UMTS.  In telecommunications there are two reasons why a handoff (handover) might be conducted: if the phone has moved out of range from one cell site (base station) and can get a better radio link from a stronger transmitter, or if one base station is full the connection can be transferred to another nearby base station.  The most basic form of handoff is that used in GSM and analog cellular networks, where a phone call in progress is redirected from one cell site and its transmit/receive frequency pair to another base station (or sector within the same cell) using a different frequency pair without interrupting the call. As the phone can be connected to only one base station at a time and therefore needs to drop the radio link for a brief period of time before being connected to a different, stronger transmitter, this is referred to as a hard handoff. This type of handoff is described as "break before make" (referring to the radio link).  In CDMA systems the phone can be connected to several cell sites simultaneously, combining the signaling from nearby transmitters into one signal using a rake receiver. Each cell is made up of one to three (or more) sectors of coverage, produced by a cell site's independent transmitters outputting through antennas pointed in different directions. The set of sectors the phone is currently linked to is referred to as the "active set". A soft handoff occurs when a CDMA phone adds a new sufficiently-strong sector to its active set. It is so called because the radio link with the previous sector(s) is not broken before a link is established with a new sector; this type of handoff is described as "make before break". In the case where two sectors in the active set are transmitted from the same cell site, they are said to be in softer handoff with each other.  There are also inter-technology handoffs where a call's connection is transferred from one access technology to another, e.g. a call being transferred from GSM to W-CDMA.

HDTV - high definition television is a television display technology that provides picture quality similar to 35 mm. HDTV generally uses digital rather than analog signal transmission. However, in Japan, the first analog HDTV program was broadcast on June 3, 1989. It required a 20 MHz channel, which is why analog HDTV broadcasting is not feasible in most countries.

High fidelity (or HiFi or hi-fi) is the reproduction of sound and image that is very faithful to the original. Hi-fi aims to achieve minimal or unnoticeable amounts of noise and distortion. The term hi-fi can be applied to any reasonable-quality home-music system. Hi-fi enthusiasts are often known as audiophiles or videophiles.

High Resolution Digital Display Capability - Provides large-screen high resolution digital display resolution: VGA - 640 x 480, SVGA - 800 x 600 or XGA - 1024 x 768. Refresh rates are compatible with most PC and Mac® refresh rates – excellent performance from 50-75Hz.

HLR - The Home Location Register or HLR is a central database that contains details of each mobile phone subscriber that is authorized to use the GSM core network.

More precisely, the HLR stores details of every SIM card issued by the mobile phone operator. Each SIM has a unique identifier called an IMSI which is one of the primary keys to each HLR record. The next important items of data associated with the SIM are the telephone numbers used to make and receive calls to the mobile phone, known as MSISDNs. The main MSISDN is the number used for making and receiving voice calls and SMS, but it is possible for a SIM to have other secondary MSISDNs associated with it for fax and data calls. Each MSISDN is also a primary key to the HLR record. Examples of other data stored in the HLR in a SIM record is:
bulletGSM services that the subscriber has requested or been given
bulletGPRS settings to allow the subscriber to access packet services
bulletCurrent Location of subscriber (VLR and SGSN)
bulletCall divert settings applicable for each associated MSISDN.
The HLR data is stored for as long as a subscriber remains with the mobile phone operator. At first glance, the HLR seems to be just a database which is merely accessed by other network elements which do the actual processing for mobile phone services. In fact the HLR is a system which directly receives and processes MAP transactions and messages. If the HLR fails, then the mobile network is effectively disabled as it is the HLR which manages the Location Updates as mobile phones roam around. As the number of mobile subscribers has grown in mobile phone operators the HLR has become a more powerful computer server rather than the traditional telephone exchange hardware in the early days of GSM.

Horizontal and Vertical Image Scaling to Fit TV Screen Audio Input with Loop-Through Output - Regular phono jacks designed to accompany the SVGA/VGA, S-Video, and composite video inputs. These inputs accept a wide variety of audio sources.

Horizontal Resolution - The smallest increment of a television picture that can be discerned in the horizontal plane. This increment is dependent upon the video bandwidth and is measured in frequency. It determines the number of lines it takes to scan an image on the screen.

HSS - The Home Subscriber Server is the master user database that supports the IMS network entities that are actually handling the calls/sessions. It contains the subscription-related information (user profiles), performs authentication and authorization of the user, and can provide information about the physical location of user. It's similar to the GSM HLR and AUC. An SLF (Subscriber Location Function) is needed when multiple HSSs are used. Both the HSS and the SLF implement the DIAMETER protocol (Cx, Dx and Sh interfaces).




I-mode - is a technical specification and business model developed by Japan’s NTT DoCoMo for delivery of Web-type content to wireless handsets.

ICD - Internet Call Diversion is a transparent routing of calls between voice and data networks. By enabling remote access equipment to communicate with carriers’ SS7 networks, the ICD supports the redirection of resource-consuming Internet traffic from the public switched telephone network (PSTN) directly onto data networks. Service providers gain the capability to end Internet call busy signals, cut dial-up connection costs and free up PSTN circuits to carry voice traffic only.

ICMP - Internet Control Message Protocol is one of the core protocols of the Internet protocol suite. It is chiefly used by networked computers' operating systems to send error messages—indicating, for instance, that a requested service is not available or that a host or router could not be reached.  ICMP differs in purpose from TCP and UDP in that it is usually not used directly by user network applications. One exception is the ping tool, which sends ICMP Echo Request messages (and receives Echo Response messages) to determine whether a host is reachable and how long packets take to get to and from that host. The version of ICMP for Internet Protocol version 4 is also known as ICMPv4, as it is part of IPv4. IPv6 has an equivalent protocol, ICMPv6.

iDEN- Integrated Digital Enhanced Network is a mobile communications technology, developed by Motorola, which provides its users the benefits of a trunked radio and a cellular telephone. Sprint Nextel is the largest U.S. retailer of iDEN services. iDEN places more users in a given spectral space, compared to analog cellular systems, by using time division multiple access (TDMA). Up to six communication channels share a 25 kHz space; some competing technologies place only one channel in 12.5 kHz. iDEN is a Motorola proprietary version of TDMA with a unique “push-to-talk” two-way radio capability. Nextel Communications is the largest iDEN operator in the U.S.

IDL - An Interface Description Language, (alternatively interface definition language) (IDL), is a computer language or simple syntax for describing the interface of a software component. It is essentially a common language for writing the "manual" on how to use a piece of software from another piece of software, in much the same fashion that a user manual describes how to use a piece of software to the user.  IDLs are used in situations where the software on either side may not share common "call semantics", referring to the way the computer language "talks" to the routines. For instance, C and Pascal have different ways of calling routines, and in general cannot call code written in the other language. IDLs are a subset of both, a general language to which both can conform to enable language-independent code.  IDLs are most commonly found in software intended to allow routines to be called on other machines, known as remote procedure call. In these cases the call semantics may vary not only between languages, but also due to the architecture of the machines themselves.  An IDL is part of Sun's ONC RPC, The Open Group's Distributed Computing Environment, Microsoft's COM, IBM's System Object Model, Mozilla's XPCOM (also known as XPIDL), the Object Management Group's CORBA, and SOAP for Web Services.

IEEE 1394 - A very fast external bus standard that supports data transfer rates of up to 400Mbps (in 1394a) and 800Mbps (in 1394b). Products supporting the 1394 standard go under different names, depending on the company. Apple, which originally developed the technology, uses the trademarked name FireWire. Other companies use other names, such as i.link and Lynx, to describe their 1394 products.  A single 1394 port can be used to connect up 63 external devices. In addition to its high speed, 1394 also supports isochronous data -- delivering data at a guaranteed rate. This makes it ideal for devices that need to transfer high levels of data in real-time, such as video devices.  Although extremely fast and flexible, 1394 is also expensive. Like USB, 1394 supports both Plug-and-Play and hot plugging, and also provides power to peripheral devices.

IEEE 802.2 - Developed by the IEEE, 802.2 defines a datalink layer standard used with 802.3, 802.4, 802.5 & 802.6. 802.2 adds several header fields to those normally used by the upper layer protocols. These fields identify what upper layer protocol is used in the frame and which network layer processes are the frames source and destination.

IEEE 802.3 - 802.3 was proposed by the IEEE. The following specifications are supported. 1base5, 10base2, 10base5, 10baseT, 10baseF, 10broad36 and 100baseX. 802.3 uses CSMA/CD as its contention method.

IEEE 802.5 - This is the IEEE standard for IBMs Token Ring spec. Token Ring operates at 4 or 16 Mbps. 802.5 does not specify any medium type, but generally UTP is used.

IEEE 802.6 - This spec represents the DQDB (Distributed Queue Dual Bus) standard. This is used in MANs, Metropolitan area networks. DQDB uses a fiber based dual bus topology that may be looped for fault tolerance. Each bus is unidirectional and both buses operate in opposite directions. DQDB allocates bandwidth by using TDM. Traffic may be sync or async.

IEEE 802.9 -  IEEE 802.9 isoEthernet.  isoEthernet provides a way to bring both Ethernet and ISDN directly to the enterprise desktop.

IETF - Internet Engineering Task Force. This is a group that develops and publishes new standards for use on the Internet, in particular those of the TCP/IP protocol suite. It is an open, all-volunteer standards organization, with no formal membership or membership requirements.  It is organized into a large number of working groups and BoFs, each dealing with a specific topic, and intended to complete work on that topic and then shut down. Each working group has an appointed chair (or sometimes several co-chairs), along with a charter that describes its focus, and what and when it is expected to produce.  The working groups are organized into areas by subject matter; each area is overseen by an area director (AD) (most areas have 2 co-AD's); the ADs appoint working group chairs. The area directors, together with the IETF Chair, form the Internet Engineering Steering Group (IESG), which is responsible for the overall operation of the IETF. The IETF is formally an activity under the umbrella of the Internet Society. The IETF is overseen by the Internet Architecture Board (IAB), which oversees its external relationships, and relations with the RFC Editor. The IAB is also jointly responsible for the IETF Administrative Oversight Committee (IAOC), which oversees the IETF Administrative Support Activity (IASA), which provides logistical, etc support for the IETF. The IAB also manages the Internet Research Task Force (IRTF), with which the IETF has a number of cross-group relations.

IGMP - Internet Group Management Protocol. This protocol is used in multicasting.

IGP - Interior Gateway Protocol refers to a routing protocol that is used within an autonomous system. The most commonly used IGPs are RIP, OSPF and IS-IS.  When using a routing protocol such as BGP in a network, the routes received have a next hop that is not necessarily directly connected. The IGP is used to "resolve" these next hops.

IM - Instant messaging is the act of instantly communicating between two or more people over a network such as the Internet Instant Messaging requires the use of a client program that hooks up an instant messaging service and differs from e-mail in that conversations are then able to happen in real time. Most services offer a presence information feature, indicating whether people on one's list of contacts are currently online and available to chat. This may be called a 'Buddy List'. In early instant messaging programs, each letter appeared as it was typed, and when letters were deleted to correct typos this was also seen in real time. This made it more like a telephone conversation than exchanging letters. In modern instant messaging programs, the other party in the conversation generally only sees each line of text right after a new line is started. Most instant messaging applications also include the ability to set a status message, roughly analogous to the message on a telephone answering machine. Popular instant messaging services on the public Internet include Qnext, MSN Messenger, AOL Instant Messenger, Yahoo! Messenger, Skype, Google Talk, .NET Messenger Service, Jabber, QQ, iChat and ICQ. These services owe many ideas to an older (and still popular) online chat medium known as Internet Relay Chat (IRC).

IMEI - The International Mobile Equipment Identity is a number unique to every GSM and UMTS mobile phone. It is usually found printed on or underneath the phone's battery and can also be found by dialing the sequence *#06# into the phone. The IMEI number is used by the GSM network to identify valid devices and therefore can be used to stop a stolen phone from accessing the network. For example, if a mobile phone is stolen, the owner can call his or her network provider and instruct them to "bar" the phone using its IMEI number. This renders the phone useless, regardless of whether the phone's SIM is changed. Unlike the ESN of CDMA and other wireless networks, the IMEI is only used to identify the device, and has no permanent or semi-permanent relation to the subscriber. Instead, the subscriber is identified by transmission of an IMSI number, which is stored on a SIM card which can (in theory) be transferred to any handset. However, many network and security features are enabled by knowing the current device being used by a subscriber.

IMIA - International Medical Informatics Association

IMP - Integrated Master Plan:  Integrated Master Planning can develop an event-based IMP for your proposal or assist your staff with IMP development.  The IMP will be unique to your company's management processes and structure.

IMS - The IP Multimedia Subsystem is a standardized Next Generation Networking (NGN) architecture for telecom operators that want to provide mobile and fixed multimedia services. It uses a Voice-over-IP (VoIP) implementation based on a 3GPP standardized implementation of SIP, and runs over the standard Internet Protocol (IP). Existing phone systems (both packet-switched and circuit-switched) are supported.  The aim of IMS is not only to provide new services but all the services, current and future, that the Internet provides. In addition, users have to be able to execute all their services when roaming as well as from their home networks. To achieve these goals, IMS uses open standard IP protocols, defined by the IETF. So, a multimedia session between two IMS users, between an IMS user and a user on the Internet, and between two users on the Internet is established using exactly the same protocol. Moreover, the interfaces for service developers are also based on IP protocols. This is why IMS truly merges the Internet with the cellular world; it uses cellular technologies to provide ubiquitous access and Internet technologies to provide appealing services.

IMS - Integrated Master Schedule. Integrated Master Planning (IMP) can prepare the IMS which expands the IMP to a working level networked schedule or assist your staff with IMS development.  During the IMP and IMS development process, all the elements of the proposal will be integrated into one master database for cross correlation and reference.

IMSI - IMSI [im-zee] is an acronym for International Mobile Subscriber Identity. This is a unique number that is associated with all GSM and UMTS network mobile phone users. The number is stored in the SIM. It is sent by the mobile to the network and is used to look up the other details of the mobile in the HLR or as locally copied in the VLR. In order to avoid the subscriber being identified and tracked by eavesdroppers on the radio interface, the IMSI is sent as rarely as possible and a randomly generated TMSI is sent instead.  An IMSI is usually fifteen digits long. However, they can be shorter (e.g. MTN SouthAfrica's are 14 digits). The first three digits are the country code (MCC), and the next digits are the network code (MNC). The MNC can be either two digits long (normal e.g. in Europe) or three digits long (normal in North America), the remaining digits, up to the maximum length are the unique subscriber number (MSIN) within the network's customer base. The IMSI conforms to the ITU E.212 numbering standard.

IMUX - Inverse multiplexer.  Re-aggregates split sub-channels in a data stream into a single channel.  See ISDN

INAP - The Intelligent Network Application Part is a signaling protocol used in the intelligent network architecture. It is part of the SS7 protocol suite, typically layered on top of the TCAP protocol.  The ITU defines several "capability levels" for this protocol, starting with Capability Set 1 (CS-1). A typical application for the IN is a Number Translation service.  For example, in the United Kingdom, 0800 numbers are freephone numbers and are translated to a geographic number using an IN platform. The Telephone exchanges decode the 0800 numbers to an IN trigger and the exchange connects to the IN. The Telephone exchange uses TCAP, SCCP and INAP and in IN terms is a Service Switching Point. It sends an INAP Initial Detection Point (IDP) message to the Service Control Point. The SCP returns an INAP Connect message, which contains a geographic number to forward the call to. INAP messages are defined using ASN.1 encoding.  SCCP is used for the routing. TCAP is used to separate the transactions apart.

Input/Output Capabilities - Features a multitude of input/output capabilities including antenna input, board interface slot, SVGA/VGA input/output, S-Video input/output, audio input/output, VGA Audio in, and composite video input/output.

Interlaced - The process of scanning whereby the alternate lines of both scanned fields fall evenly between each other.

Internet - the extensive, worldwide computer network available to the public. An internet is a more general term informally used to describe any set of interconnected computer networks that are connected by internetworking.  The Internet, or simply the Net, is the publicly accessible worldwide system of interconnected computer networks that transmit data by packet switching using a standardized Internet Protocol (IP) and many other protocols. It is made up of thousands of smaller commercial, academic, domestic and government networks. It carries various information and services, such as electronic mail, online chat and the interlinked web pages and other documents of the World Wide Web.

Internet Protocol Suite - is the set of communications protocols that implement the protocol stack on which the Internet and most commercial networks run. It is sometimes called the TCP/IP protocol suite, after the two most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were also the first two defined. The internet protocol suite — like many protocol suites — can be viewed as a set of layers, each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted. The OSI model describes a fixed set of seven layers that some vendors prefer and that can be roughly compared to the IP suite. This comparison can cause confusion or give further insight into the IP suite.



Application DNS, TLS/SSL, TFTP, FTP, HTTP, IMAP, IRC, NNTP, POP3, SIP, SMTP, SNMP, SSH, TELNET, BitTorrent, RTP, rlogin, ENRP, …
Transport TCP, UDP, DCCP, SCTP, IL, RUDP, …
Network IP (IPv4, IPv6), ICMP, IGMP, ARP, RARP, …
Data Link Ethernet, Wi-Fi, Token ring, PPP, SLIP, FDDI, ATM, DTM, Frame Relay, SMDS, ...
Physical wire, radio, fiber optic, Carrier pigeon - RS-232, EIA-422, RS-449, EIA-485, 10BASE2, 10BASE-T, ...

Internetworking  - Connecting computer networks together.  LAN to LAN, LAN to WAN, and WAN to WAN.  Internetworking is accomplished using Brouters, Routers, and Gateways.

Interoperability - A state of complete compatibility among devices required to operate together with each other, with reference to a specified feature set or standard. This is an important consideration when mixing non-ITU-T codecs from different manufacturers and when mixing ITU-T codecs from different manufacturers which may support different capabilities. Remember that ITU-T codec systems revert to the highest common denominator for operation.

Interworking - a telecommunications term, used mostly in network convergence and Next Generation Networks, referring to interworking between different networks or network protocols like: IP and ISDN, FR and ATM, RTP and AAL2, etc.

Intranet - An intranet is a LAN used internally in an organization to facilitate communication and access to information that is sometimes access-restricted. Sometimes the term refers only to the most visible service, the internal web site. The same concepts and technologies of the Internet such as clients and servers running on the Internet protocol suite are used to build an intranet. HTTP and other internet protocols are commonly used as well, especially FTP and email. There is often an attempt to use internet technologies to provide new interfaces with corporate 'legacy' data and information systems.  Access from the organization's internal network to the internet itself, if need be, will be through a firewall with a gateway. Traffic going through the gateway can be monitored by the organization's security department. This means that organizations that allow their staff internet access can normally determine which internet web sites are being viewed, block access to specific sites they don't want them to see (such as pornographic sex sites), and even trace offenders who persistently attempt to view them. They can also block certain types of web content (such as objects) which they consider a particular security risk.  Where external email access is provided, known sources of spam and specific types of email attachment can be blocked by the organization. It should also be noted that emails sent and received this way can be required to be produced by the organization in the event of legal action against it by a third party.

IP - The Internet Protocol. It was developed by the government for use in internetworking multiple computer networks together.  IP is the network layer for the TCP/IP protocol suite that is the basis of the Internet. IP is also widely used on Ethernet networks.  IP is used for the transmission of data, voice, video and other information over the Internet.

IPDC - Internet Protocol Device Control protocol is used to manage the network access devices and to request the set-up and teardown of calls.  Also see Megaco.

IP Multicast - A system for sending IP transmissions out only one time, but allowing for multiple users to receive it. This would reduce the bandwidth required for audio and video broadcasting over the Internet, but it is not widely used yet.

IPsec - IP security is a standard for securing Internet Protocol (IP) communications by encrypting and/or authenticating all IP packets. IPsec provides security at the network layer.  IPsec protocols are defined by RFCs 2401–2412.  IPsec is a set of cryptographic protocols for: 1- securing packet flows and 2- key exchange. Of the former, there are two: Encapsulating Security Payload (ESP) provides authentication, data confidentiality and message integrity; Authentication Header (AH) provides authentication and message integrity, but does not offer confidentiality. Originally AH was only used for integrity and ESP was used only for encryption; authentication functionality was added subsequently to ESP.  Currently only one key exchange protocol is defined, the IKE (Internet Key Exchange) protocol.  Click here for IPsec configuration.

IPv4 - IPv4 is version 4 of the Internet Protocol (IP) and it is the first version of the Internet Protocol to be widely deployed. IPv4 is the dominant network layer protocol on the internet and when ignoring its successor — IPv6 — it is the only protocol used on the internet. It is described in IETF RFC 791 (September 1981) which obsoleted RFC 760 (January 1980). The United States Department of Defense also standardized it as MIL-STD-1777.IPv4 is a data-oriented protocol to be used on a packet switched internetwork (e.g., Ethernet). It is a best effort protocol in that it doesn't guarantee delivery. It doesn't make any guarantees on the correctness of the data; it may result in duplicated packets and/or packets out-of-order. All of these things are addressed by an upper layer protocol (e.g., TCP, UDP). The entire purpose of IP is to provide unique global computer addressing to ensure that two computers over the internet can uniquely identify one another.

IPv6 - Internet Protocol version 6 (IPv6) is a network layer standard used by electronic devices to exchange data across a packet-switched internetwork. It follows IPv4 as the second version of the Internet Protocol to be formally adopted for general use.IPv6 is intended to provide more addresses for networked devices, allowing, for example, each cell phone and mobile electronic device to have its own address. IPv4 supports 4.3×109 (4.3 billion) addresses, which is inadequate to give one (or more if they possess more than one device) to every living person. IPv6 supports 3.4×1038 addresses, or 5×1028(50 octillion) for each of the roughly 6.5 billion people alive today.  Addresses in IPv6 are 128 bits long.  IPsec, the protocol for IP network-layer encryption and authentication, is an integral part of the base protocol suite in IPv6.  Invented by Steve Deering and Craig Mudge at Xerox PARC, IPv6 was adopted by the Internet Engineering Task Force in 1994, when it was called "IP Next Generation" (IPng). (Incidentally, IPv5 was not a successor to IPv4, but an experimental flow-oriented streaming protocol intended to support video and audio.) As of December 2005, IPv6 accounts for a tiny percentage of the live addresses in the publicly-accessible Internet, which is still dominated by IPv4.  The adoption of IPv6 has been slowed by the introduction of network address translation (NAT), which partially alleviates address exhaustion. The U.S. Government has specified that all federal agencies must deploy IPv6 by 2008. It is expected that IPv4 will be supported alongside IPv6 for the foreseeable future.

Invar Mask Picture Tube - Institutional Televisions feature the Invar Shadow Mask that eliminates "doming" or flashes of light in the corners of the picture that result from heating and cooling of the electron beam. With the invar mask, the picture is clearer, brighter, and more consistent.

IR - Infrared radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. The name means "below red" (from the Latin infra, "below"), red being the color of visible light of longest wavelength. Infrared radiation spans three orders of magnitude and has wavelengths between 700 nm and 1 mm.

IRC - Internet Relay Chat is a form of instant communication over the Internet. It is mainly designed for group (many-to-many) communication in discussion forums called channels, but also allows one-to-one communication.

ISDN - Integrated Services Digital Network. A set of protocols and interface standards that effectively constitutes an integrated telephone network. ISDN can transmit digital data and voice, ideal for videoconferencing.

ISDN BRI - Basic Rate Interface.  Delivers service on one or two 64 kbps full duplex “B” channels plus one 16 kbps “D” channel for control and signaling

ISDN PRI - Primary Rate Interface. 23B+D channels (30B + D in Europe) with 64 kbs D channel.  Provides 1.54 Mbps in North America and up to 2.048 Mbps in Europe.

ISO - International Organization for Standardization or International Standardization Organization.  Establishes and coordinates worldwide standards for electronic information exchange.

Isochronous - Used to describe the transmission of continuous media, implying finite size data samples generated at fixed intervals.  For example, multimedia streams require an isochronous transport mechanism to ensure that data is delivered as fast as it is displayed and to ensure that the audio is synchronized with the video.  Certain types of networks, such as ATM, are said to be isochronous because they can guarantee a specified throughput. Likewise, new bus architectures, such as IEEE 1394, support isochronous delivery.

Isochronous Ethernet - The main idea of Isochronous Ethernet is to combine the advantages of a shared high speed communications channel for bursty packed based data traffic like Ethernet and synchronous/isochronous channels for multimedia traffic where minimal delay and guaranteed bandwidth is important.  Isochronous Ethernet uses the same CAT-3 twisted pair wires as 10 Base-T, therefore switching to this new system does not require rewiring an existing 10 Base-T installation.  Isochronous Ethernet uses a different encoding scheme than traditional Ethernet and gains 6.384 MBit/s bandwidth. This way it can provide the usual 10 MBit/s for data traffic and use the additional capacity for the multimedia traffic. The 6.384 MBit/s are split up into 96 ISDN 64 KBit/s channels and some others for signaling and control.

ISUP - ISDN User Part.  Signaling System No. 7 protocol.

ITU - The International Telecommunications Union (ITU), formerly known as CCITT, headquartered in Geneva, Switzerland is an international organization within which governments and the private sector coordinate global telecom networks and services.

ITV or IATV - InterActive TeleVideo



J-Carrier - Japanese version of the T-carrier system of North America.

J2EE - Java Platform, Enterprise Edition or Java EE (formerly known as Java 2 Platform, Enterprise Edition or J2EE up to version 1.4), is a programming platform—part of the Java platform—for developing and running distributed multi-tier architecture Java applications, based largely on modular software components running on an application server. The Java EE platform is defined by a specification. Java EE is also considered informally to be a standard because providers must agree to certain conformance requirements in order to declare their products as Java EE compliant; albeit with no ISO or ECMA standard.  Java EE includes several API specifications, such as JDBC, client-side applets, RPC, CORBA, and defines how to coordinate them. Java EE also features some specifications unique to Java EE for components. These include Enterprise Java Beans, servlets, portlets (following the Java Portlet specification), JavaServer Pages and several web service technologies. This allows the developer to create an enterprise application that is portable between platforms and scalable, while integrating with legacy technologies.

J2ME - see Java Platform, Micro Edition or Java ME.

JAIN - Java APIs for Integrated Networks (JAIN) is an activity within the Java Community Process, developing APIs for the creation of telephony (voice and data) services. Originally, JAIN stood for Java APIs for Intelligent Network. The name was later changed to Java APIs for Integrated Networks to reflect the widening scope of the project. The JAIN activity consists of a number of "Expert Groups", each developing a single API specification.  JAIN is part of a general trend to open up service creation in the telephony network so that, by analogy with the Internet, openness should result in a growing number of participants creating services, in turn creating more demand and better, more targeted services.  A major goal of the JAIN APIs is to abstract the underlying network, so that services can be developed independent of network technology, be it traditional PSTN or Next Generation Network.  The JAIN effort has produced around 20 APIs, in various stages of standardization, ranging from Java APIs for specific network protocols, such as SIP and TCAP, to more abstract APIs such as for call control and charging, and even including a non-Java effort for describing telephony services in XML.  There is overlap between JAIN and Parlay/OSA because both address similar problem spaces. However, as originally conceived, JAIN focused on APIs that would make it easier for network operators to develop their own services within the framework of Intelligent Network (IN) protocols. As a consequence, the first JAIN APIs focused on methods for building and interpreting SS7 messages and it was only later that JAIN turned its attention to higher-level methods for call control. Meanwhile, at about the same time JAIN was getting off the ground, work on Parlay began with a focus on APIs to enable development of network services by non-operator third parties.

JAVA - was invented in 1995.  JAVA is a programming language from Sun Microsystems designed primarily for writing software on the web host to download over the internet to PC end users.  Initially JAVA was used to bring motion to static Web pages.  For more information go to: http://java.sun.com

JavaBeans - JavaBeans are software components written in the Java programming language. The JavaBeans specification by Sun Microsystems defines them as "reusable software components that can be manipulated visually in a builder tool".  In spite of many similarities, JavaBeans should not be confused with Enterprise JavaBeans (EJB), a server-side component technology that is part of Java EE.

Java EE - Java Platform, Enterprise Edition or Java EE (formerly known as Java 2 Platform, Enterprise Edition or J2EE up to version 1.4), is a programming platform—part of the Java platform—for developing and running distributed multi-tier architecture Java applications, based largely on modular software components running on an application server. The Java EE platform is defined by a specification. Java EE is also considered informally to be a standard because providers must agree to certain conformance requirements in order to declare their products as Java EE compliant; albeit with no ISO or ECMA standard.  Java EE includes several API specifications, such as JDBC, client-side applets, RPC, CORBA, and defines how to coordinate them. Java EE also features some specifications unique to Java EE for components. These include Enterprise Java Beans, servlets, portlets (following the Java Portlet specification), JavaServer Pages and several web service technologies. This allows the developer to create an enterprise application that is portable between platforms and scalable, while integrating with legacy technologies.

Java ME - Java Platform, Micro Edition or Java ME (formerly referred to as Java 2 Platform, Micro Edition or J2ME), is a collection of Java APIs for the development of software for resource constrained devices such as PDAs, cell phones and other consumer appliances. Java ME is formally a specification, although the term is frequently used to also refer to the runtime implementations of the specification. Java ME was developed under the Java Community Process as JSR 68. The evolution of the platform has abandoned the umbrella Java Specification Request in favor of separate JSRs for the different flavors of Java ME.  Java ME was designed by Sun Microsystems and is a replacement for a similar technology, PersonalJava. Java ME has become a popular option for creating games for cell phones, as they can be emulated on a PC during the development stage and easily uploaded to the phone. This contrasts with the difficulty of developing, testing, and loading games for other special gaming platforms such as those made by Nintendo, Sony, and others, as expensive system-specific hardware and kits are required.  Sun Microsystems has tended not to provide free binary implementations of its Java ME runtime environment for mobile devices, rather relying on third parties to provide their own, in stark contrast to the numerous binary implementations it provides for the full Java platform standard on server and workstation machines. One of the notable omissions is for Microsoft Windows Mobile (Pocket PC) based devices, despite an open letter campaign to Sun to release a rumored complete project "Captain America" which is such an implementation.

Java SE - Java Platform, Standard Edition or Java SE (formerly known up to version 5.0 as Java 2 Platform, Standard Edition or J2SE), is a collection of Java programming language APIs useful to many Java platform programs. The Java Platform, Enterprise Edition includes all of the classes in the Java SE, plus a number which are more useful to programs running on servers than on workstations.  Starting with the J2SE 1.4 version (Merlin), the Java SE platform has been developed under the Java Community Process. JSR 59 was the umbrella specification for J2SE 1.4 and JSR 176 specified J2SE 5.0 (Tiger). As of 2006, Java SE 6 (Mustang) is being developed under JSR 270.  The following are descriptions of some of the primary Java SE packages. For a complete list of packages see the J2SE 5.0 API Javadocs.

Java Portlet Specifications - defines a contract between the portlet container and portlets and provides a convenient programming model for portlet developers. The Java Portlet Specification V1.0 was developed under the Java Community Process as JSR 168.

The Java Portlet Specification V1.0 introduces the basic portlet programming model with:

two phases of action processing and rendering in order to support the Model-View-Controller pattern.


portlet modes, enabling the portal to advise the portlet what task it should perform and what content it should generate


window states, indicating the amount of portal page space that will be assigned to the content generated by the portlet


portlet data model, allowing the portlet to store view information in the render parameters, session related information in the portlet session and per user persistent data in the portlet preferences


a packaging format in order to group different portlets and other J2EE artifacts needed by these portlets into one portlet application which can be deployed on the portal server.

JAVA Servlet - The Java Servlet API allows a software developer to add dynamic content to a Web server using the Java platform. The generated content is commonly HTML, but may be other data such as XML. Servlets are the Java counterpart to dynamic web content technologies such as CGI, PHP or ASP. Servlets can maintain state across many server transactions by using HTTP cookies, session variables or URL rewriting. The Servlet API, contained in the Java package hierarchy javax.servlet, defines the expected interactions of a web container and a servlet. A web container is essentially the component of a web server that interacts with the servlets. The web container is responsible for managing the lifecycle of servlets, mapping a URL to a particular servlet and ensuring that the URL requester has the correct access rights. A Servlet is an object that receives requests (ServletRequest) and generates a response (ServletResponse) based on the request. The API package javax.servlet.http defines HTTP subclasses of the generic servlet (HttpServlet) request (HttpServletRequest) and response (HttpServletResponse) as well as an (HttpSession) that tracks multiple requests and responses between the web server and a client. Servlets may be packaged in a WAR file as a Web application. Moreover, servlets can be generated automatically by JavaServer Pages (JSP), or alternately by template engines such as WebMacro. Often servlets are used in conjunction with JSPs in a pattern called "Model 2", which is a flavor of the model-view-controller pattern.

JavaServer Faces - JavaServer Faces (JSF) is a Java-based Web application framework that simplifies the development of user interfaces for Java EE applications. Out of the box, JSF uses JavaServer Pages for its display technology, but JSF can also accommodate other display technologies, such as XUL, for example. JSF includes:

bulletA set of APIs for representing user interface (UI) components and managing their state, handling events and input validation, defining page navigation, and supporting internationalization and accessibility
bulletA default set of UI components
bulletTwo JavaServer Pages (JSP) custom tag libraries for expressing a JavaServer Faces interface within a JSP page.
bulletA server-side event model
bulletState management
bulletManaged Beans (JavaBeans created with dependency injection)
The JSF specification was developed under the Java Community Process as JSR 127, which defined JSF 1.0 and 1.1. As of 2006, JSF 1.2 is being developed as JSR 252.

JavaServer Pages - JavaServer Pages (JSP) is a Java technology that allows software developers to dynamically generate HTML, XML or other types of documents in response to a Web client request. The technology allows Java code and certain pre-defined actions to be embedded into static content. The JSP syntax adds additional XML tags, called JSP actions, to be used to invoke built-in functionality. Additionally, the technology allows for the creation of JSP tag libraries that act as extensions to the standard HTML or XML tags. Tag libraries provide a platform independent way of extending the capabilities of a Web server.  JSPs are compiled into Java Servlets by a JSP compiler. A JSP compiler may generate a servlet in Java code that is then compiled by the Java compiler, or it may generate byte code for the servlet directly. In either case, it is helpful to understand how the JSP compiler transforms the page into a Java servlet. For an example, consider the input here, and its resulting generated Java Servlet here. Architecturally speaking, JSP can be viewed as a high-level abstraction of servlets that is implemented as an extension of the Servlet 2.1 API. Both servlets and JSPs were originally developed by Sun Microsystems. Starting with version 1.2 of the JSP specification, JavaServer Pages have been developed under the Java Community Process. JSR 53 defines both the JSP 1.2 and Servlet 2.4 specifications and JSR 152 defines the JSP 2.0 specification. As of 2006 the JSP 2.1 specification is being developed under JSR 245.

Jitter - A flickering on a display screen. Besides a monitor or connector malfunction, jitter can be caused by a slow refresh rate.

JMS - The Java Message Service (JMS) API is a Java Message Oriented Middleware (MOM) API for sending messages between two or more clients. JMS is a specification developed under the Java Community Process as JSR 914. As of 2006, the current version is JMS 1.1.

JTAPI - JAVA Telephony API.  A set of modularly-designed, application programming interfaces for Java-based computer telephony applications.  JTAPI consists of one Core package and several extension packages.  JTAPI applications are portable across platforms without modifications.



Kerberos - is a network authentication protocol developed by MIT in the 1980s.  It is designed to provide strong authentication for client/server applications by using secret-key cryptography.

KVM Switch - Keyboard/Video/Mouse Switch.  A switched box used to control multiple computers from a single keyboard, monitor, and mouse.



Latency - The length of time it takes a packet to move from source to destination; delay.

Laser - Light Amplification by Stimulated Emission of Radiation is a device which uses a quantum mechanical effect, stimulated emission, to generate a coherent beam of light from a lasing medium of controlled purity, size, and shape. The output of a laser may be a continuous, constant-amplitude output (known as CW or continuous wave), or pulsed, by using the techniques of Q-switching, modelocking, or gain-switching. In pulsed operation, much higher peak powers can be achieved. A laser medium can also function as an optical amplifier when seeded with light from another source. The amplified signal can be very similar to the input signal in terms of wavelength, phase, and polarization; this is particularly important in optical communications. The verb "to lase" means "to produce coherent light" or possibly "to cut or otherwise treat with coherent light", and is a back-formation of the term laser.

Lawful Intercept - Lawful interception (aka wiretapping) of telecommunications. Interception of telecommunications by law enforcement authorities (LEA's) and intelligence services, in accordance with local law and after following due process and receiving proper authorization from competent authorities. Various countries have different rules with regards to lawful interception. In the United States the law is known as CALEA, in CIS countries as SORM.  With the existing Public Switched Telephone Network (PSTN), Lawful Interception (LI) is performed by applying a 'tap' on the telephone line of the target in response to a warrant from a Law Enforcement Agency (LEA). However, Voice over IP (VoIP) technology has enabled the mobility of the end-user, so it is no longer possible to guarantee the interception of calls based on tapping a physical line.  Whilst the detailed requirements for LI differ from one jurisdiction to another, the general requirements are the same. The LI system must provide transparent interception of specified traffic only, and the subject must not be aware of the interception. The service provided to other users must not be affected during interception.

Light - is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. The three basic dimensions of light (and of all electromagnetic radiation) are: intensity (or brilliance or amplitude, perceived by humans as the brightness of the light), frequency (or wavelength, perceived by humans as the color of the light), and polarization (or angle of vibration and not perceivable by humans under ordinary circumstances).  The speed of light is 227,000 kilometers per second (approximately 141,050 miles per second).

Line Doublers - An increased definition television unit that doubles the number of scan lines in a video picture. This fills the space between the original lines, making them less noticeable.

Local PreviewTM - Channel Guide - Automatically displays pre-programmed channel guide every time the television is turned on. After choosing the channel to view, channel guide fades off the screen to be displayed again when called up using the remote.

Long Power Cords - Using extension cords violates safety regulations in some commercial buildings.  Commercial televisions with an 8'-12' power cord for convenient access to electrical outlets.

Loop-Through Capabilities - Institutional Televisions offer users the ability to loop composite video, S-Video, or even VGA from one set to another set from a single source. This means that multiple sets can display exactly the same programming at the same time from one VCR or other video source.

Lossless compression - Refers to data compression techniques in which no data is lost. For most types of data, lossless compression techniques can reduce the space needed by only about half.  Lossless compression technique is used when compressing data files and programs.  Also, The Graphics Interchange File (GIF) is an image format used on the Web that provides lossless compression.

Lossy compression - Refers to data compression techniques in which some amount of data is lost.  Only certain types of data can tolerate lossy compression.  Lossy compression technologies attempt to eliminate redundant or unnecessary information. Most video compression technologies, such as MPEG, use a lossy technique.  Also, the JPEG image file, commonly used for photographs and other complex still images on the Web, is an image that has lossy compression. Using JPEG compression, the creator can decide how much loss to introduce and make a trade-off between file size and image quality.

Low Cost Solution - upgrade and add capabilities without having to buy new televisions.

Luminance - The monochrome or black and white part (Y) of a video signal that provides brightness information.  Measured in lux, lumens, or footcandles.



MAP - Mobile Application Part (MAP) is a standard of the European Telecommunications Standards Institute (ETSI) for enabling GSM subscribers that roam between different wireless service operators’ networks to make and receive voice calls. MAP provides an application layer for the various nodes in the core mobile network to communicate with each other in order to provide services to mobile phone users.  MAP relies on ETSI/3GPP Standards :a-) in GSM Only versions (before R4) : TR 09.02 ; b-) From 3G/GSM R99 versions : TS 29.002.  MAP is implemented on the SS7 family of protocols, and it uses SCCP Sub System Numbers. The main operations executed by MAP are: 1-) Mobility Management, 2-) Operation and Maintenance, 3-) Call Handling, 4-) Supplementary Services, and 5-) Short Message Service.

Marquee Channel TM - This feature allows Institutional Televisions to default to a pre-selected channel whenever they're turned on. Users may specify any channel or source as the marquee channel.

MBONE - Multicast Backbone. The MBONE is a system of transmitting audio and video over a multicast network. Mostly available at universities and government facilities, the MBONE can be thought of as a testbed for technologies that will eventually be promulgated across the larger internet. The MBONE has been replaced on the vBNS and Abilene by native multicast support.

Megaco - a contraction of "Media Gateway Controller", Megaco is a signaling protocol, used between a Media Gateway and a Media Gateway Controller (also known as a Call Agent or a Soft Switch) in a VoIP network. It defines the necessary signaling mechanism to allow a Media Gateway Controller (Call agent) to control gateways in order to support voice/fax calls between PSTN-IP or IP-IP networks. This protocol is defined by IETF RFC 3525 and was the result of joint work of IETF and ITU. It is also known as H.248. H.248 is the name given to it by the ITU, Megaco is the IETF name.

Message - or messaging in its most general meaning is an object of communication. Depending on the context, the term may apply to both the information contents and its actual presentation.

In the communications discipline, a message is information which is sent from a source to a receiver. Some common definitions include:
bulletAny thought or idea expressed briefly in a plain or secret language, prepared in a form suitable for transmission by any means of communication.
bulletAn arbitrary amount of information whose beginning and end are defined or implied.
bulletRecord information, a stream of data expressed in plain or encrypted language (notation) and prepared in a format specified for intended transmission by a telecommunications system.
In the Actor model a message is similarly an Actor itself that is sent asynchronously from one Actor to another. In languages such as Smalltalk-80 and Objective-C an instance of a class method is called (confusingly) a message.

Metadata - Data about data. Meta data describes how and when and by whom a particular set of data was collected, and how the data is formatted. Meta data is essential for understanding information stored in data warehouses.  Types of Metadata: Relational database metadata, Data warehouse metadata, General IT metadata, File system metadata, Image metadata, Program metadata, Metamodels, Strange metadata, and Digital library metadata.

Metadata registry is a central location in an organization where metadata definitions are stored and maintained in a controlled method.

MHz (as in 8 MHz) - An abbreviation for megahertz. This is a unit of measurement and refers to a million cycles per second. For example bandwidth, in television context, is measured in megahertz.

MIDI - Musical Instrument Digital Interface is a standard for connecting electronic musical instruments and computers. MIDI files can be thought of as digital sheet music, where the computer acts as the musician playing back the file. MIDI files are much smaller than digital audio files, but the quality of playback will vary from computer to computer.

MMS - Multimedia Messaging Service is a technology for transmitting not only text messages, but also various kinds of multimedia content (e.g. images, audio, and/or video clips) over wireless telecommunications networks using the Wireless Application Protocol (WAP). It is standardized by 3GPP and 3GPP2.

Mobility Management - Mobility Management is one of the major functions of a GSM or a UMTS network that allows mobile phones to work. The aim of mobility management is to track where the mobile subscribers are, so that calls, SMS and other mobile phone services can be delivered to them.  A GSM or UMTS network, like all cellular networks, is a radio network of individual cells, known as base stations. Each base station covers a small geographical area which is part of a uniquely identified location area. By integrating the coverage of each of these base stations, a cellular network provides a radio coverage over a very much wider area. A group of base stations is called a location area, or a routing area.  The location update procedure allows a mobile device to inform the cellular network, whenever it moves from one location area to the next. Mobiles are responsible for detecting location area codes. When a mobile finds that the location area code is different from its last update, it performs another update by sending to the network, a location update request, together with its previous location, and its Temporary Mobile Subscriber Identity (TMSI). There are several reasons why a mobile may provide updated location information to the network. Whenever a mobile is switched on or off, the network may require it to perform an IMSI attach or IMSI detach location update procedure. Also, each mobile is required to regularly report its location at a set time interval using a periodic location update procedure. Whenever a mobile moves from one location area to the next while not on a call, a random location update is required. This is also required of a stationary mobile that reselects coverage from a cell in a different location area, because of signal fade. Thus a subscriber has reliable access to the network and may be reached with a call, while enjoying the freedom of mobility within the whole coverage area.

Modular Tuner - X-channel (e.g. 181-channel) modular tuner with Auto Programming.

Modulation - is the addition of information (or the signal) to an electronic or optical signal carrier. Modulation can be applied to direct current (mainly by turning it on and off), to alternating current, and to optical signals. Morse code, invented for telegraphy and still used in amateur radio, uses a binary (two-state) digital code similar to the code used by modern computers. For most of radio and telecommunication today, the carrier is alternating current (AC) in a given range of frequencies. Common modulation methods include: Amplitude modulation (AM), in which the voltage applied to the carrier is varied over time, Frequency modulation (FM), in which the frequency of the carrier waveform is varied in small but meaningful amounts, Phase modulation (PM), in which the natural flow of the alternating current waveform is delayed temporarily.  These are also known as continuous wave modulation methods to distinguish them from pulse code modulation (PCM), which is used to encode both digital and analog information in a binary way. Radio and television broadcast stations typically use AM or FM. Most two-way radios use FM, although some employ a mode known as single sideband (SSB). More complex forms of modulation are Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM). Optical signals are modulated by applying an electromagnetic current to vary the intensity of a laser beam.

MOM - Message Oriented Middleware is a category of inter-application communication software that relies on asynchronous message passing as opposed to a request/response metaphor. Most message oriented middleware (MOM) is based around a message queue system, although there are implementations that rely on a broadcast or multicast messaging system.  MOM requires an extra component in the architecture, the message transfer agent.

Monitor Output Capability - Monitor output allows simple recording of whatever source is resident on the television screen.

Monitoring - The status of every TV in the network is continuously monitored, providing verification that televisions are on-line and operating in compliance with content distribution requirements (power on, correct channel and volume, valid signal, etc.). Quick notification is provided at the computer head-end control when a TV is off-line, malfunctioning, disconnected, or being used for unauthorized programming. System operation is documented in log files, providing a record of scheduled event control commands, system outages, and televisions requiring attention.

MPEG - MPEG (Moving Picture Experts Group) is a series of ISO standards for digital video and audio, designed for different uses and data rates. More information can be found at: http://www.mpegif.org

MPEG-1 - The initial MPEG standard, designed to encode full motion video so it could be played back off of a CD (150 kb/s). The bit rate of a standard MPEG1 is 1.5Mbps. MPEG-1 has a frame size of 352x240 pixels, which gives a picture quality slightly better than VHS video tape. MPEG-1 included three audio standards, most video systems use MPEG-1 layer 1 or layer 2 audio. MPEG-1 layer 3 audio (commonly known as MP3), is being used widely for audio on the Internet.

MPEG-2 was a follow-on standard supporting higher data rates, and thus higher quality. MPEG-2 is the standard used in DVD video players, most digital satellite systems in North America, and in the new North American Digital TV system.

MPEG-3 was abandoned as its planned functionality was included in MPEG-2.

MPEG-4 is a draft standard that will be better suited for use on the Internet. MPEG4 delivers video at comparable quality to MPEG1 at a much lower bit rate. MPEG-4 also supports a wide variety of elements that can be transmitted separately and combined to form the video frame, such as a talking head in one stream and the background in another. That is, MPEG4 allows manipulation of objects within the video stream (addition, subtraction, object manipulation, etc.). If you don't like where a chair is in the video, you can move it (providing the chair has been coded as a moveable object, of course).  For more information try the following site: http://bmrc.berkeley.edu/frame/research/mpeg/mpegfaq.html



MPEG-7 - formally named “Multimedia Content Description Interface”, is a standard for describing the multimedia content data that supports some degree of interpretation of the information’s meaning, which can be passed onto, or accessed by, a device or a computer code. MPEG-7 is not aimed at any one application in particular; rather, the elements that MPEG-7 standardizes support as broad a range of applications as possible.  More information about MPEG-7 can be found at the MPEG home page (http://www.chiariglione.org/mpeg/)  and the MPEG-7 Alliance website (http://www.mpeg-industry.com). These web pages contain links to a wealth of information about MPEG, including much about MPEG-7, many publicly available documents, several lists of ‘Frequently Asked Questions’ and links to other MPEG-7 web pages.

MPLS - Multi-protocol Label Switching.  A computer networking and telecommunications layer 2.5 protocol as it lies between Layer 2 and Layer 3 of the OSI reference model.  MPLS has adopted many technically sound ideas from ATM.  Computer networking are mostly based on large packet switching (e.g. Ethernet 1500-byte) coupled with the advancement in the large modern optical networks more specifically the switching speed (10 Gbps and well beyond) and the reduced transmission error rates (almost errorless) advancement in modern optical networks have opened the door to new network protocols.  MPLS is such a protocol, designed mainly to forward IP datagrams and Ethernet traffic.   MPLS can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames.  In the field of VPNs, L2TPv3 is emerging as a potential competitor to MPLS, particularly in existing networks with IP-only cores. MPLS is currently in use in large "IP Only" networks, and is standardized by IETF in RFC 3031.  In practice, MPLS is mainly used to forward IP datagrams and Ethernet traffic. Major applications of MPLS are Telecommunications traffic engineering and MPLS VPN.

MSISDN - The Mobile Station Integrated Services Digital Network is the mobile equivalent of ISDN. Used as a value, MSISDN refers to the Mobile Subscriber ISDN Number, which is a max 15-digit number. There are mobile phones on the market that can have several MSISDNs in one SIM Card. E.g. a German MSISDN and a French MSISDN in one SIM card would allow the user to be reached under two numbers.

MTSO - Mobile Telephone Switching Office - The central switch that controls the entire operation of a cellular system. It is a sophisticated computer that monitors all cellular calls, tracks the location of all cellular-equipped vehicles traveling in the system, compiling call information for billing, connects all of the individual cell towers to the Central Office (CO).  The MTSO arranges handoffs by monitoring the relative signal strength of your cellular phone as reported by each of the cell towers, and switching your conversation to the cell tower which will give you the best possible reception.  The MTSO is an operations center that connects the landline PSTN system to the mobile phone system.

Multi-tier Architecture - In software engineering, multi-tier architecture (often referred to as n-tier architecture) is a client-server architecture in which an application is executed by more than one distinct software agent. For example, an application that uses middleware to service data requests between a user and a database employs multi-tier architecture. The most widespread use of "multi-tier architecture" refers to three-tier architecture.

Multipath - In wireless telecommunications, multipath is the propagation phenomenon that results in radio signals' reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflection from terrestrial objects, such as mountains and buildings.  The effects of multipath include constructive and destructive interference, and phase shifting of the signal. This causes Rayleigh fading, named after Lord Rayleigh. The standard statistical model of this gives a distribution known as the Rayleigh distribution.  Rayleigh fading with a strong line of sight content is said to have a Rician distribution, or to be Rician fading.  In facsimile and television transmission, multipath causes jitter and ghosting, seen as a faded duplicate image to the right of the main image.  In digital radio communications (such as GSM) multipath can cause errors and affect the quality of communications. The errors are due to Inter-symbol interference (ISI). Equalisers are often used to correct the ISI. Alternatively, techniques such as orthogonal frequency division modulation and Rake receivers may be used.

Multiplexing - More information can be conveyed in a given amount of time by dividing the bandwidth of a signal carrier so that more than one modulated signal is sent on the same carrier. Known as multiplexing, the carrier is sometimes referred to as a channel and each separate signal carried on it is called a sub-channel. (In some usages, each sub-channel is known as a channel.) The device that puts the separate signals on the carrier and takes them off of received transmissions is a multiplexer. Common types of multiplexing include frequency-division multiplexing (FDM) and time-division multiplexing (TDM). FDM is usually used for analog communication and divides the main frequency of the carrier into separate subchannels, each with its own frequency band within the overall bandwidth. TDM is used for digital communication and divides the main signal into time-slots, with each time-slot carrying a separate signal.

Multipoint Conferencing Server (MCS) (also MCU)  - A hardware or software H.323 device that allows multiple video conferencing (or audio or data) users to connect together. Without an MCS typically only point to point conferences can take place. Commonly supports voice activated switching, where whoever is talking is broadcast to all users, but new systems support "Hollywood squares", where multiple windows show each participant. ITU-T standard H.231 describes the standard way of doing this. Many current systems only support H.320 (ISDN) but many vendors are working to upgrade their products to support H.323 (LAN, Internet) as well. In the H.320 space, this functionality is referred to as a multipoint control unit (MCU). Sometimes these terms are used interchangeably, although they refer to somewhat different implementations.


Multithreading - see Thread.

Multimedia and Computer Display Capability - Accepts XGA, SVGA, VGA and Mac Signals, composite video with audio, S-Video with audio for greater picture and sound performance in conjunction with computers, video cameras, VCRs, DVD players, Laser Disc players, Web browsers and satellite receiver systems.

Multiple Input/Output Capabilities - Institutional Televisions feature a multitude of input/output capabilities including board interface slot, S-Video input/output, two audio inputs, Composite Video input/output, Smart PlugTM interface, and RF input.

MVNO - A Mobile Virtual Network Operator (MVNO) functions as a wireless service operator in the marketplace though it does not own an actual wireless network. Host Network Operator (HNO) is a related term. The HNO is the actual owner and operator of the wireless network, which includes the towers and all of the switching equipment.




NAPTR - Naming Authority Pointer and is a newer type of DNS record that supports regular expression based rewriting. Several NAPTR records can be chained together creating fairly sophisticated URI rewriting rules. A record can go through any number of rewrites before reaching a terminal condition.  For example, after translating the phone number +1-770-555-1212 into the URI as described by E.164, DDDS is used to transform it using rewrite rules gathered from NAPTR records. The BIND configuration for the records returned from a query for might look like:


 IN NAPTR 100 10 "u" "sip+E2U" "!^.*$!sip:information@pbx.example.com!i" .

 IN NAPTR 102 10 "u" "smtp+E2U" "!^.*$!mailto:information@example.com!i" .

Of these two records, the first has an order value of 100 which is lower than 102 so it is picked first. The preference of 10 is unimportant as no other rules have an order of 100. The "u" signifies a terminal rule in ENUM and URI applications, so the output of this rewrite will be the answer we are looking for. If we support the service designated with the key "sip+E2U", we won't go on to investigate other rules with higher order values. The rewrite regular expression "!^.*$!sip:information@pbx.example.com!i" is evaluated transforming our original request of into sip:information@pbx.example.com. In the regular expression, the exclamation mark '!' will be our delimiter (we avoid the use of '/' and '\' because they may be interpreted as escape sequences somewhere else). The "^.*$" in the RE says "starting at the beginning, including any characters and ending at the end" (in other words, everything) is changed to "sip:information@pbx.example.com" and 'i' ignores case. (Observant readers will notice that the 'i' doesn't matter, given the use of ".*") For those familiar with Perl REs, the equivalent RE could be written as "/^.*$/mailto:information@example.com/i". So the resulting URI "sip:information@pbx.example.com" will be used. If we didn't support SIP, we would effectively fall back to the rule resulting in "mailto:information@example.com".

Narrowband - (narrow bandwidth) refers to a signal which occupies only a small amount of space on the radio spectrum -- the opposite of broadband or wideband.  This is entirely relative to what is being described; for example, an FM broadcast station takes up 150~200kHz on the FM band, whereas a TV station's audio is narrowband, taking up only 25kHz, and weatheradio broadcasts are even narrower than that. It is also very often used to describe radio antennas, called narrowband when they are designed specifically for one frequency or channel only instead of a wide range.  Narrowband can also be used with the audio spectrum to describe sounds which occupy a narrow range of frequencies. In telephony narrowband is usually considered to cover frequencies 300-3400Hz.

NAS - Network Access Server is a single point of access to a remote resource. A client connects to  the NAS and then the NAS connects to another resource (e.g. RADIUS) to authenticate the client.

NAT-PT/NAPT-PT: from 3GPP, NAT-PT uses a pool of globally unique IPv4 addresses for assignment to IPv6 nodes on a dynamic basis as sessions are initiated across the IP version boundaries. NAT-PT binds addresses in IPv6 network with addresses in IPv4 network and vice versa to provide transparent routing between the two IP domain without requiring any changes to end points, like the UE. NAT-PT needs to track the sessions it supports and mandates that inbound and outbound data for a specific session traverse the same NAT-PT router.

NAPT-PT provides additional translation of transport identifier (e.g., TCP and UDP port numbers, ICMP query identifiers). This allows the transport identifiers of a number of IPv6 hosts to be multiplexed into the transport identifiers of a single assigned IPv4 address. See RFC 2766 [33] for more details.

Net1 System Television Control - Adds networking capability to television and allows television to be controlled from a central location via an RF distribution system.

Network Engineering - In telecommunication, the term network engineering has the following meanings: 1.)  In telephony, the discipline concerned with (a) determining internetworking service requirements for switched networks, and (b) developing and implementing hardware and software to meet them. 2.) In computer science, the discipline of hardware and software engineering to accomplish the design goals of a computer network. 3.) In radio communications, the discipline concerned with developing network topologies.

Network Planning and Design - Network planning and design is an iterative process, encompassing topological design, network-synthesis, and network-realization, and is aimed at ensuring that a new network or service meets the needs of the subscriber and operator.  The process can be tailored according to each new network or service.  This is an extremely important process which must be performed before the establishment of a new telecommunications network or service.

Network Switching Subsystem - Network Switching Subsystem is the component of a GSM system that carries out switching functions and manages the communications between mobile phones and the Public Switched Telephone Network (PSTN). It is owned and deployed by mobile phone operators and allows mobile phones to communicate with each other and telephones in the wider telecommunications network. The architecture closely resembles a telephone exchange, but there are additional functions which are needed because the phones are not fixed in one location. Each of these functions handle different aspects of mobility management and are described in more detail below. The Network Switching Subsystem, also referred to as the GSM core network, usually refers to the circuit-switched core network, used for traditional GSM services such as voice calls, SMS, and Circuit Switched Data calls. There is also an overlay architecture on the GSM core network to provide packet-switched data services and is known as the GPRS core network. This allows mobile phones to have access to services such as WAP, MMS, and Internet access. All mobile phones manufactured today have both circuit and packet based services, so most operators have a GPRS network in addition to the standard GSM core network.

Network Topology - A network topology is the pattern of links connecting pairs of nodes of a network. A given node has one or more links to others, and the links can appear in a variety of different shapes. The simplest connection is a one-way link between two devices. A second return link can be added for two-way communication. Modern communications cables usually include more than one wire in order to facilitate this, although very simple bus-based networks have two-way communication on a single wire.  Network topology is determined only by the configuration of connections between nodes; it is therefore a part of graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types are not a matter of network topology, although they may be affected by it in an actual physical network.

Networking Capability - NetCard TV allows a single television, group of televisions or all televisions to be switched on, controlled, and tuned to a channel for a displayed modulated video signal all from a single location. NetCard TV allows a school-wide system of televisions to access television programming, computer displays, or a myriad of video-based programs, and much more.

Non-Interlaced - Also called progressive scan, this a method by which all the video scan lines are presented on the screen in one sweep instead of two (also see interlaced).

NTSC (National Television Standards Committee) - This is the television standard for North America, Japan, and certain countries in South America - 525 lines/60 Hz (90 Hz Refresh).



OFDM - Orthogonal frequency-division multiplexing, also sometimes called discrete multitone modulation (DMT), is a complex modulation technique for transmission based upon the idea of frequency-division multiplexing (FDM) where each frequency channel is modulated with a simpler modulation. In OFDM the frequencies and modulation of FDM are arranged to be orthogonal with each other which almost eliminates the interference between channels. Although the principles and some of the benefits have been known for 40 years, it is made popular today by the lower cost and availability of digital signal processing components.  A number of extra useful benefits, particularly multipath resistance, arise when the data is coded with some Forward Error Correction (FEC) scheme prior to modulation called channel coding. This is called Coded OFDM abbreviated to COFDM.

OLAP - On Line Analytical Processing. It is an approach to quickly provide the answer to analytical queries that are dimensional in nature. It is part of the broader category business intelligence, which also includes ETL, relational reporting and data mining. The typical applications of OLAP are in business reporting for sales, marketing, management reporting, business performance management (BPM), budgeting and forecasting, financial reporting and similar areas. The term OLAP was created as a slight modification of the traditional database term OLTP (On Line Transaction Processing).  Databases configured for OLAP employ a multidimensional data model, allowing for complex analytical and ad-hoc queries with a rapid execution time. Nigel Pendse has suggested that an alternative and perhaps more descriptive term to describe the concept of OLAP is Fast Analysis of Shared Multidimensional Information (FASMI). They borrow aspects of navigational databases and hierarchical databases that are speedier than their relational kin.  In 2001 Microsoft and Hyperion announced the XML for Analysis specification, which was endorsed by most of the OLAP vendors. It uses MDX as a query language, MDX became the de-facto standard in the OLAP world.  There are a few types of OLAP: 1-) Multidimensional OLAP - MOLAP is the 'classic' form of OLAP and is sometimes referred to as just OLAP. MOLAP uses database structures that are generally optimally attributes such as time period, location, product or account code. The way that each dimension will be aggregated is defined in advance by one or more hierarchies.  2-) Relational OLAP - ROLAP works directly with relational databases, the base data and the dimension tables are stored as relational tables and new tables are created to hold the aggregated information. 3-) Hybrid OLAP (HOLAP) - There is no clear agreement across the industry as to what constitutes "Hybrid OLAP", except that a database will divide data between relational and specialized storage. For example, for some vendors, a HOLAP database will use relational tables to hold the larger quantities of detailed data, and use specialized storage for at least some aspects of the smaller quantities of more-aggregate or less-detailed data.  In comparing the different OLAP types: Each type has certain benefits; however, there is disagreement about the specifics of the benefits between providers. MOLAP is better on smaller sets of data, it is faster to calculate the aggregations and return answers and does need less storage space.  ROLAP is considered more scalable. However, large volume pre-processing is difficult to implement efficiently so it is frequently skipped. ROLAP query performance can therefore suffer.  HOLAP is between the two in all areas, but it can pre-process quickly and scale well. All types though are prone to database explosion. Database explosion is a phenomenon causing vast amount of storage space being used by OLAP databases when certain but frequent conditions are met: high number of dimensions, pre-calculated results and sparse multidimensional data. The difficulty in implementing OLAP comes in forming the queries, choosing the base data and developing the schema, as a result of which most modern OLAP products come with huge libraries of pre-configured queries. Another problem is in the base data quality - it must be complete and consistent.  Some Other known OLAP types: 1-) WOLAP - Web-based OLAP. 2-) DOLAP - Desktop OLAP. 3-) RTOLAP - Real-Time OLAP: Whilst many OLAP Servers such as Microsoft Analysis Services store pre-calculating consolidations and calculated elements to achieve rapid response times a Real Time OLAP Server will calculate the values on the fly, when they are required. The essential characteristic of RTOLAP system is that it holds all the data in RAM.

Optical Amplifier - In fiber optics, an optical amplifier is a device that amplifies an optical signal directly, without the need to convert it to an electrical signal, amplify it electrically, then reconvert it to an optical signal.

Optical Fiber - is a transparent thin fiber, usually made of glass, for transmitting light. Fiber optics is the branch of science and engineering concerned with optical fibers.

OSA - The Open System Architecture is part of the 3rd generation mobile telecommunications network or UMTS. OSA describes how services are architected in an UMTS network.  The standards for OSA are being developed as part of the 3rd Generation Partnership Project (3GPP). The standards for OSA are published by ETSI and 3GPP.  The API for OSA is called Parlay, (or Parlay/OSA or OSA/Parlay) as the APIs are developed jointly in collaboration by 3GPP, ETSI, and the Parlay Group. These APIs can be freely downloaded from the web.

OSPF - Open Shortest Path First is a link-state, hierarchical Interior Gateway Protocol (IGP) routing protocol. Dijkstra's algorithm is used to calculate the shortest path tree. It uses cost as its routing metric. A link state database is constructed of the network topology which is identical on all routers in the area. OSPF is perhaps the most widely used IGP in large networks. It can operate securely, using MD5 to authenticate peers before forming adjacencies, and before accepting link-state advertisements. A natural successor to RIP, it was VLSM capable or classless from its inception. A newer version of OSPF (OSPFv3) now supports IPv6 as well. Multicast extensions to OSPF (MOSPF) have been defined, however these are not widely used. OSPF can "tag" routes, and propagate these tags along with the routes. An OSPF network can be broken up into smaller networks. A special area called the backbone area forms the core of the network, and other areas are connected to it. Inter-area routing goes via the backbone. All areas must connect to the backbone; if no direct connection is possible, a virtual link may be established. Routers in the same broadcast domain or at each end of a point to point link form adjacencies when they have discovered each other. The routers elect a designated router (DR) and backup designated router (BDR) which act as hub to reduce traffic between routers. OSPF uses both unicast and multicast to send 'hello packets' and link state updates. Multicast addresses and are used. In contrast to RIP or BGP, OSPF does not use TCP or UDP but uses IP directly, using IP protocol 89.



P2P : Peer-to-Peer networks and Peer-to-Peer services. computer network is a network that relies primarily on the computing power and bandwidth of the participants in the network rather than concentrating it in a relatively low number of servers. P2P networks are typically used for connecting nodes via largely ad hoc connections. Such networks are useful for many purposes. Sharing content files (see file sharing) containing audio, video, data or anything in digital format is very common, and real-time data, such as telephony traffic, is also passed using P2P technology.  A pure peer-to-peer network does not have the notion of clients or servers, but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network. This model of network arrangement differs from the client-server model where communication is usually to and from a central server. A typical example for a non peer-to-peer file transfer is an FTP server where the client and server programs are quite distinct, and the clients initiate the download/uploads and the servers react to and satisfy these requests.  Some networks and channels, such as Napster, OpenNAP, or IRC @find, use a client-server structure for some tasks (e.g., searching) and a peer-to-peer structure for others. Networks such as Gnutella, Freenet, or JXTA use a peer-to-peer structure for all purposes, and are sometimes referred to as true peer-to-peer networks, although Gnutella is greatly facilitated by directory servers that inform peers of the network addresses of other peers.  Peer-to-peer architecture embodies one of the key technical concepts of the internet, described in the first internet Request for Comments, "RFC 1, Host Software" [1] dated 7 April 1969. More recently, the concept has achieved recognition in the general public in the context of the absence of central indexing servers in architectures used for exchanging multimedia files.  The concept of peer to peer is increasingly evolving to an expanded usage as the relational dynamic active in distributed networks, i.e. not just computer to computer, but human to human. Yochai Benkler has developed the notion of commons-based peer production to denote collaborative projects such as free software. Associated with peer production are the concept of peer governance (referring to the manner in which peer production projects are managed) and peer property (referring to the new type of licenses which recognize individual authorship but not exclusive property rights, such as the GNU General Public License and the Creative Commons License).

PABX - A Private Automatic Branch Exchange (PABX) is an automatic telephone switching system within a private enterprise. Originally, such systems - called private branch exchanges (PBX) - required the use of a live operator. Since almost all private branch exchanges today are automatic, the abbreviation "PBX" usually implies a "PABX."

Packet - A unit of information sent across a (packet-switched) network. A packet generally contains the destination address as well as the data to be sent.

Pan and Zoom - Scroll through oversized graphics and text with the convenience of pan and zoom. When the Zoom button is pressed, the upper left corner of the screen is selected at maximum magnification. Then you can pan left, right, up, or down through the rest of the document using the arrow cursor buttons.

Parlay - The Parlay Group is a technical industry consortium (founded 1998) that specifies APIs for the telephone network. These APIs enable the creation of services by organizations both inside and outside of the traditional carrier environment. In fact, it is hoped that services can be created by IT developers, rather than telephony experts.  Important Parlay APIs include: call control, conferencing, user interaction (audio and text messaging), and charging. The APIs are specified in the CORBA Interface definition language and WSDL. The use of CORBA enables remote access between the Parlay gateway and the application code. A set of Java mappings allow the APIs to be invoked locally as well. A major goal of the APIs is to be independent of the underlying telephony network technology (e.g. CDMA vs. GSM vs. landline SS7).  In 2003 the Parlay Group released a new set of web services called Parlay X. These are a much simpler set of APIs intended to be used by a larger community of developers. The Parlay X web services include Third Party Call Control (3PCC), Location and simple payment. The Parlay X specifications complement the more complex yet powerful Parlay APIs. Parlay X implementations are now (Sept 2004) in commercial service from BT and Sprint.  Parlay work historically stems from the TINA effort. Parlay is somewhat related to JAIN, and is currently (early 2003) completely unrelated to the Service Creation Community.  The Parlay Group works closely with ETSI and 3GPP, the Parlay specifications are co-published by all three bodies. Within 3GPP Parlay is part of Open Services Architecture, so we often use the term Parlay/OSA.  The objective of Parlay/OSA is to provide an API that is independent of the underlying networking technology and of the programming technology used to create new services. As a result the Parlay/OSA APIs are specified in UML. There are then a set of realizations, or mappings, for specific programming environments: CORBA/IDL, Java, and WSDL.

Parlay X - Parlay X is a set of telecommunications Web services. Parlay X is designed to enable software developers to use capabilities from the telecom network (e.g. such as location, or the ability to set up a call) in applications. The Parlay X Web services are defined by the Parlay Group, and are also a part of the 3GPP Release 6 Specifications. The principle behind Parlay X is that since Web services are widely used in the IT industry, they are a good basis for telecommunication service creation. There is a large number of developers and programmers who understand Web services, and there is a wide variety of development tools. The Parlay X APIs define a set of simple-to-use, high-level, telecom-related Web services. Parlay X Version 1, published in May 2003, defines web services for Third Party Call, Network Initiated Third Party Call, Send SMS, Receive SMS, Send Message, Receive Message, Amount Charging, Volume Charging, User Status and Terminal LocationContrast Parlay X to the more complex, but functionally richer, Parlay APIs. A typical Parlay X API operation is Send SMS() which may be mapped to a series Parlay API methods. Parlay X Version 2 specifications were published by ETSI in March 2005. Equivalent specifications are part of 3GPP Release 6.Parlay X Version 2.1 specifications are currently [Feb 2006] in development. Parlay X has been implemented by a number of telecom operators, including BT, Korea Telecom and Sprint.

PBX - A subscriber-owned telecommunications exchange that usually includes access to the public switched network. 2. A switch that serves a selected group of users and that is subordinate to a switch at a higher level military establishment. 3. A private telephone switchboard that provides on-premises dial service and may provide connections to local and trunked communications networks. Note 1: A PBX operates with only a manual switchboard; a private automatic exchange (PAX) does not have a switchboard, a private automatic branch exchange (PABX) may or may not have a switchboard. Note 2: Use of the term "PBX" is far more common than "PABX," regardless of automation.

PCS - Personal Communications Services (PCS) was a name given by the FCC to a new set of wireless services and spectrum allocated in the 1990s. Today, in popular use, it refers to the 1900-MHz cellular frequency band.

PDC - Personal Digital Cellular (PDC) is a version of TDMA technology used exclusively in Japan.

PDM - Product Data Management is a category of computer software that aims to create an automatic link between product data and a database. The information being stored and managed (on one or more file serves) will include engineering data such as CAD models and drawing and their associated documents. The package may also include product visualization data. The central database will also manage metadata such owner of a file and release status of the components. The package will: control check-in and check-out of the product data to multi-user; carryout engineering change management and release control on all versions/issues of components in a product; build and manipulate the product structure BOM (Bill of Materials) for assemblies; and assist in configurations management of product variants. This enables automatic reports on product costs, etc. Furthermore, PDM enables companies producing complex products to spread product data in to the entire PLM launch-process. This significantly enhances the effectiveness of the launch process.  Most larger CAD vendors have some kind of PDM offering. Standard off-the-shelf CAD (Autodesk, etc) has PDM functionality built in. CAD vendors in an industrial niche usually have a separate closed offering (example, textile CAD - Lectra, Gerber, etc). Other are not industry specific and can handle multiple CAD systems (example UGS ‘s Teamcenter)

PHS - Personal HandyFone System (PHS) is a Japan-only TDMA technology. Originally, the difference between PDC and PHS systems was that PDC was true cellular while PHS provided voice and data access but did not support moving from one cell to another. PHS became the favorite wireless technology for teenagers because of its low cost. Several years ago, groups of teens could be seen standing on street corners under PHS cells talking on their PHS phones.

Pixel - A term used mostly inside the U.S. that is an abbreviation for “picture element” or the most fundamental component of a raster display. (See Pel.)

PLM - Product Lifecycle Management is a term used for the process of managing the entire lifecycle of a product from its conception, through design and manufacture to service and disposal. PLM is a set of capabilities that enable an enterprise to effectively and efficiently innovate and manage its products and related services throughout the entire business lifecycle. It is one of the four cornerstones of a corporation's IT digital structure. All companies need to manage communications and information with its customers (CRM-Customer_Relationship_Management) and its suppliers (SCM-Supply chain management) and the resources within the enterprise (ERM-Enterprise Relationship Management). For a manufacturing engineering company it must also develop, describe, manage and communicate information about its products (PLM).

PLMN - In telecommunication, a public land mobile network is a network that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public.  Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones or other wireless enabled user equipment and land based radio transmitters or radio base stationsPLMNs interconnect with other PLMNs and PSTNs for telephone communications or with internet service providers for data and internet access.

Plug and Play Technology - Designed so you don't have to worry about complicated equipment, messy hook-ups, or extra wires or cords. Just plug in and play, and open the door to amazing visual displays.

PM - Project Management. A project is a temporary endeavor undertaken to create a unique product or service.  A project is consider temporary since once the projects objectives are met, the project team will break-up and go onto other projects. The goal of a project is to create something new, or unique.  All projects have three basic elements: tasks, resources and time. These are interrelated and any change in one has an effect on the other two. This is one area where Microsoft Project excels. Whenever you make any changes, the affect of those changes will become instantly visible through Microsoft Project's graphical presentation of your project.

PNNI - Private Network Node Interface or Private Network-to-Network Interface (PNNI) protocol. is used by most ATM networks supporting SPVPs, SPVCs, and SVCs.  PNNI uses the same shortest path first algorithm used by OSPF and IS-IS to route IP packets to share topology information between switches and select a route through a network. PNNI also includes a very powerful summarization mechanism to allow construction of very large networks, as well as a call admission control (CAC) algorithm that determines whether sufficient bandwidth is available on a proposed route through a network to satisfy the service requirements of a Virtual Circuit or Virtual Path.

PoC - Push to Talk over Cellular is the Motorola and Nokia versions of PTT, and are based on 2.5G packet-switched networks (CDMA by Motorola, GPRS by Nokia) and use SIP and RTP protocols. The Open Mobile Alliance is defining PoC as part of the IMS (IP Multimedia System) framework. A pre-standard version of PoC is also defined by the industry consortium made up of Motorola, Nokia, Ericsson, Siemens AG, AT&T Wireless, and Cingular Wireless with the aim of creating a commercial offering enabling inter-operability between vendors.  Also see PTT.

POP - In wireless parlance, the number of wireless POPs refer to the total population covered by a wireless service operator’s license.  ISP POP is a Point of Presence where subscribers can connect to the internet.

Portlets - Portlets are pluggable user interface components that are managed and displayed in a portal. Portlets produce fragments of markup code that are aggregated into a portal page. Typically, following the desktop metaphor, a portal page is displayed as a collection of non-overlapping portlet windows, where each portlet window displays a portlet. Hence a portlet (or collection of portlets) resembles a web-based application that is hosted in a portal. Portlet applications include email, weather reports, discussion forums, and news. Portlet standards are intended to enable software developers to create portlets that can be plugged in any portal supporting the standards.  The purpose of the Web Services for Remote Portlets interface is to provide a web services standard that allows for the "plug-n-play" of portals, other intermediary web applications that aggregate content, and applications from disparate sources.  The Java Portlet Specification (JSR168) enables interoperability between portlets and web portals. This specification defines a set of APIs for portal computing addressing the areas of aggregation, personalization, presentation and security.  Apache Pluto is a reference implementation of JSR168. Other than the reference implementation, a number of vendors provide commercial implementations of the portal container. Two of the leading vendors are IBM and BEA Systems. These vendors provide standards based implementations but also provide extensions not yet approved by the standards body. Furthermore a number of open-source portal solutions support JSR168 such as Apache's Jetspeed-2 Enterprise Portal and Liferay Portal.

Pot - An electronic component that is used to vary, or control, the amount of current that flows through an electronic circuit.  A potentiometer is also referred to as a pot.

POTS - Plain Old Telephone Service, refers to the standard telephone service that most homes use. In contrast, telephone services based on high-speed, digital communications lines, such as ISDN and FDDI, are not POTS. The main distinctions between POTS and non-POTS services are speed and bandwidth. POTS is generally restricted to about 52 Kbps (52,000 bits per second).  The POTS network is also called the public switched telephone network (PSTN).   POTS should not be confused with pot, an abbreviation of potentiometer.  POTS services include: full duplex voice path with limited frequency range (300-3400Hz), Dial Tone and Ringing Signals, Subscriber Dialing, Operator Services (such as Directory Assistance, Long Distance, and Conference Calling assistance).

Power Lock - This feature forces the default power setting to the "ON" position. This means that the power can't be turned off at the front of the set and that, in the event of a power failure, the television comes back on as soon as the power does. It also means that users can control the power to multiple sets from a single circuit breaker.

Power Management - This feature forces the default power to the "ON" position, preventing the sets from being turned off while being used.

Presence Information - In computer and telecommunications networks, presence information conveys a presentity's availability and willingness to communicate. A client publishes presence information to other systems' users—sometimes called watchers or subscribers—to convey its communication state. Presence information has wide application in voice over IP and instant messaging. A user may publish a variety of presence states to indicate their communication status. This published state informs others that wish to contact the user of their availability and willingness to communicate. The most common use of presence today is the status indicator displayed on most instant messaging clients. A more simple everyday example is the 'on-hook' or 'off-hook' state of a telephone receiver, resulting in a distinctive ring tone for caller. Some states that offer extended information on the user's availability are "free for chat", "away", "do not disturb", and "out to lunch", which are often seen on many modern instant messaging clients. In fact, users and communication applications can create arbitrary presence states, since there is no standardization of state itself. Presence is different from traditional 'on-hook' telephone status in that it deals with the user not the device.  Presence becomes interesting for communication systems when it spans a number of different communication channels. The idea that multiple communication devices can combine state, to provide an aggregated view of a user's presence has been termed Multiple Points of Presence (MPOP). MPOP becomes even more powerful when it is automatically inferred from passive observation of a user's actions. This idea is already familiar to instant messaging users who have their status set to "Away" (or equivalent) if their computer keyboard is inactive for some time. Extension to other devices could include whether the user's cell phone is on, whether they are logged into their computer or perhaps checking their electronic calendar to see if they are in a meeting or on vacation. For example, if a user's calendar was marked as out of office and their cell phone was on, they might be considered in a "Roaming" state.  MPOP status can then be used to automatically direct incoming messages across all contributing devices. For example "Out of office" might translate to a system directing all messages and calls to the user's cell phone. The status "Do not disturb" might automatically save all messages for later and send all phone calls to voicemail. Presence, particularly MPOP, requires collaboration between a number of electronic devices (for example IM client, home phone, cell phone and electronic calendar). To date, presence has only seen wide scale implementation in closed, SPOP (Single Point of Presence, where a single device publishes state) systems. For presence to work in an MPOP environment, multiple devices must be able to intercommunicate.2.5G and 3G cell phone networks promise the possibility of users publishing the presence of their cell phone handsets. In the workplace, private messaging servers offer the possibility of MPOP within a company or work team.

XMPP allows for MPOP by assigning each client a "resource" (a specific identifier) and a priority number for each resource. A message directly to the user's ID would go to the resource with highest priority, although messaging a specific resource is possible by using the form user@domain/resource.

Currently there are several working groups trying to standardize a presence protocol: The XML-based XMPP or Extensible Messaging and Presence Protocol was designed and currently maintained by the Jabber Software Foundation. It is the base of the Jabber IM protocol, which is a robust and widely extended protocol, it is also the protocol used by Google Talk. In October 2004, the XMPP working group at IETF published the RFC documents 3920, 3921, 3922 and 3923, to standardize the core XMPP protocol. Another standardization effort is SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE). SIMPLE specifies extensions to the SIP protocol which deal with a publish and subscribe mechanism for presence information and sending instant messages. SIMPLE has an IETF working group, trying to also standardize this protocol.

Priority Channel - Allows the set to default to a pre-selected channel when powered on.

Programmable Channel Blanking - Provides a means to force the picture to be blanked without affecting the audio. Perfect for audio only services, such as FM-radio.

Programmable Channel Ring - Like the volume management, this feature offers the user a limited range of flexibility. TV sets can be programmed to receive only selected channels or inputs, eliminating all others that aren't programmed.

Pro Plus Performance Package - Upgrades television with stereo dbx(R) sound, digital comb filter, event programming, 24-hour clock, easy A/V switching and 29-button Universal Remote.

Project Network - A project network is a graph (flow chart) depicting the sequence in which a project's terminal elements are to be completed by showing terminal elements and their dependencies.

PSTN - Public Switched Telephone Network refers to the international telephone system based on copper wires carrying analog voice data. This is in contrast to newer telephone networks base on digital technologies, such as ISDN and FDDI.  Telephone service carried by the PSTN is often called Plain Old Telephone Service (POTS).

PTT - Push to talk is a method of conversing on half-duplex communication lines, including two-way radio, by pushing a button in order to send, allowing voice communication to be transmitted from you, and releasing to let voice communication be received.  The term has come to be more commonly known as referring to a feature that is available on certain more recent mobile phone models. It allows the mobile phone, when in a special mode, to function as a digital two-way radio in push-to-talk operation (in a fashion similar to the "trunking" feature of newer commercial and public-safety two-way radios). Only one person at a time can talk, by pressing a PTT button, and one or several others can listen instantly. The service connects mobile phone users with each other within seconds. Currently, PTT users have to belong to the same mobile operator's (carrier's) network in order to talk to one another. PTT commonly does not use up the regular airtime minutes that are available for general voice calls, it uses the GPRS connection, on which the amount of data transmitted is billed, and not the minutes of conversation. Nextel Communications introduced mobile push to talk several years ago using iDEN and is currently the leader in this industry. iDEN technology is also used by SouthernLinc in the southeastern US, and as well as several other carriers worldwide.  Recently, Verizon Wireless and Sprint PCS in the United States, Advanced Info Service (AIS) in Thailand, Telstra in Australia and also Bell Mobility (known as 10-4 service) (CDMA) and Telus Mobility (known as MIKE) (iDEN) in Canada launched their push to talk services. And more operators all over the world have announced intentions to launch similar services.  Also see PoC.



QCIF - A standard related to CIF, QCIF (Quarter CIF), transfers one fourth the amount of data and is suitable for videoconferencing systems on slower connections or telephone lines.

QoS - Quality of Service: In the fields of packet-switched networks and computer networking, the traffic engineering term QoS (pronounced "que-oh-ess") refers to the probability of the telecommunication network meeting a given traffic contract, or in many cases is used informally to refer to the probability of a packet succeeding in passing between two points in the network. In the field of telephony, telephony QoS refers to lack of noise and tones on the circuit, appropriate loudness levels etc., and includes grade of service.  Isochronous traffic requires fixed real-time continuous sequential bitrates, and is very sensitive to loss and transmission and processing delays.  Some of the problems affecting the performance of packet based networks are:


dropped packets - the routers might fail to deliver (drop) some packets if they arrive when their buffers are already full. Some, none, or all of the packets might be dropped, depending on the state of the network, and it is impossible to determine what happened in advance. The receiving application must ask for this information to be retransmitted, possibly causing severe delays in the overall transmission.


delay - it might take a long time for a packet to reach its destination, because it gets held up in long queues, or takes a less direct route to avoid congestion. Alternatively, it might follow a fast, direct route. Thus delay is very unpredictable.


jitter - packets from source will reach the destination with different delays. This variation in delay is known as jitter and can seriously affect the quality of streaming audio and/or video.


out-of-order delivery - when a collection of related packets are routed through the Internet, different packets may take different routes, each resulting in a different delay. The result is that the packets arrive in a different order to the one with which they were sent. This problem necessitates special additional protocols responsible for rearranging out-of-order packets once they reach their destination.


error - sometimes packets are misdirected, or combined together, or corrupted, while en route. The receiver has to detect this and, just as if the packet was dropped, ask the sender to repeat itself.


The following are some of the application requiring QoS:

bulletstreaming multimedia may require guaranteed throughput
bulletIP telephony or Voice over IP (VoIP) may require strict limits on jitter and delay
bulletVideo Teleconferencing (VTC) requires low jitter
bulletdedicated link emulation requires both guaranteed throughput and imposes limits on maximum delay and jitter
bulleta safety-critical application, such as remote surgery may require a guaranteed level of availability (this is also called hard QoS).

These types of service are called inelastic, meaning that they require a certain level of bandwidth to function - any more than required is unused, and any less will render the service non-functioning. By contrast, elastic applications can take advantage of however much or little bandwidth is available.  Obtaining QoS:

bulletPer call
bulletIn call
bulletIn advance: When the expense of mechanisms to provide QoS is justified, network customers and providers typically enter into a contractual agreement termed an (SLA, Service Level Agreement) which specifies guarantees for the ability of a network/protocol to give guaranteed performance/throughput/latency bounds based on mutually agreed measures, usually by prioritizing traffic.
bulletReserving resources: Resources are being reserved at each step on the network for the call as it is set up. An example is RSVP, Resource Reservation Protocol.

QoS mechanisms: Quality of Service can be provided by generously over provisioning a network so that all packets get a quality of service sufficient to support QoS-sensitive applications. This approach is relatively simple, and is economically feasible for many broadband networks. The performance is reasonable, particularly if the user is willing to sometimes accept some degradation. For example, commercial VOIP services are increasingly replacing traditional telephone service even though no QoS mechanisms are usually operating between the user's connection to his ISP and the VOIP provider's connection to a different ISP. For narrowband networks more typical of enterprises and local governments, however, the costs of bandwidth can be substantial and over provisioning is hard to justify. In these situations, two distinctly different philosophies were developed to engineer preferential treatment for packets which require it.  Early work used the "IntServ" philosophy of reserving network resources. In this model, applications used the Resource Reservation Protocol (RSVP) to request and reserve resources through a network. While IntServe mechanisms do work, it was realized that in a broadband network typical of a larger service provider, Core routers would be required to accept, maintain, and tear down thousands or possibly tens of thousands of reservations. It was believed that this approach would not scale with the growth of the Internet, and in any event was antithetical to the notion of designing networks so that Core routers do little more than simply switch packets at the highest possible rates. The second and currently accepted approach is "DiffServ" or differentiated services. In the diffserve model, packets are marked according to the type of service they need. In response to these markings, routers and switches use various queuing strategies to tailor performance to requirements. (At the IP layer, differentiated services code point (DSCP) markings use the 6 bits in the IP packet header. At the MAC layer, VLAN IEEE 802.1q and IEEE 802.1D can be used to carry essentially the same information). Routers supporting diffserve use multiple queues for packets awaiting transmission from bandwidth constrained (e.g., wide area) interfaces. Router vendors provide different capabilities for configuring this behavior, to include the number of queues supported, the relative priorities of queues, and bandwidth reserved for each queue. In practice, when a packet must be forwarded from an interface with queuing, packets requiring low jitter (e.g., VOIP or VTC) are given priority over packets in other queues. Typically, some bandwidth is allocated by default to network control packets (e.g., ICMP and routing protocols), while best effort traffic might simply be given whatever bandwidth is left over.  Additional mechanisms may be used to further engineer performance, to include:

bulletfirst in first out (FIFO)
bulletweighted round robin, WRR
bulletclass based weighted fair queuing
bulletweighted fair queuing
bulletbuffer tuning
bulletcongestion avoidance
bulletRED, WRED - Lessens the possibility of port queue buffer tail-drops and this lowers the likelihood of TCP global synchronization
bulletpolicing and Traffic shaping

As mentioned, while diffserv is used in many sophisticated enterprise networks, it has not been widely deployed in the Internet. Internet peering arrangements are already complex, and there appears to be no enthusiasm among providers for supporting QoS across peering connections, or agreement about what policies should be supported in order to do so.  QoS skeptics further point out that if you are dropping many packets on elastic low-QoS connections, you are already dangerously close to the point of congestion collapse on your inelastic high-QoS applications, without any way of further dropping traffic without violating traffic contracts.  In addition to the local governmental rules and regulations, the following criteria need to be addressed in a QoS network design: service security and service Performance/Cost ratio.

Quantization - In the MPEG compression sequence, this step follows the Discrete Cosine Transform (DCT) and reduces the high-frequency components, leaving a softer picture but offering greater compression.  It uses fewer bits offering greater compression.  It uses fewer bits to describe the same overall quantity of information but with larger quantum steps.  JPEG and MPEG use uniform quantization, in which all the Quantization steps are of the same size.

QuickTime - A file-format and architecture developed by Apple for use with digital audio and video. Available on most computing platforms. A future version (Quicktime3) will support streaming.



RealAudio - A proprietary system for streaming audio (and now video) over the internet. Before Real Audio, users had to download an entire audio file before they could listen to it. Also supports real-time broadcast of audio and video programs. Many radio stations now broadcast on the internet using Real Audio.

Real time - A transmission that occurs right away, without any perceptible delay. Very important in video conferencing, as much delay will make the system very unusable.  Occurring immediately. The term is used to describe a number of different computer features. For example, real-time operating systems are systems that respond to input immediately. They are used for such tasks as navigation, in which the computer must react to a steady flow of new information without interruption. Most general-purpose operating systems are not real-time because they can take a few seconds, or even minutes, to react.  Real time can also refer to events simulated by a computer at the same speed that they would occur in real life. In graphics animation, for example, a real-time program would display objects moving across the screen at the same speed that they would actually move.

Remote Cloning - Settings for televisions in the system can be cloned and duplicated throughout the network, all from the head-end computer control. Any television’s settings including picture settings and institutional settings (auto power-on, minimum/maximum volume, etc.) can be downloaded as a "template", and then uploaded ("cloned") to other televisions throughout the network eliminating the need to configure each television individually at its physical location.

Replay Attack - A replay attack is a form of network attack in which a valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and retransmits it, possibly as part of a masquerade attack. Suppose Alice wants to prove her identity to Bob. Bob requests her password as proof of identity, which Alice dutifully provides (possibly after some transformation like a hash function); meanwhile, Mallory is eavesdropping the conversation and keeps the password. After the interchange is over, Mallory connects to Bob posing as Alice; when asked for a proof of identity, Mallory sends Alice's password read from the last session, which Bob must accept. A way to avoid replay attacks is using session tokens: Bob sends a one-time token to Alice, which Alice uses to transform the password and send the result to Bob (e.g. computing a hash function of the session token appended to the password). On his side Bob performs the same computation; if and only if both values match, the login is successful. Now suppose Mallory has captured this value and tries to use it on another session; Bob sends a different session token, and when Mallory replies with the captured value it will be different than Bob's computation. Session tokens should be chosen by a (pseudo-) random process. Otherwise Mallory may be able to guess some future token and convince Alice to use that token in her transformation. Mallory can then replay her reply at a later time, which Bob will accept. Bob can also send nonce but should then include a Message authentication code (MAC), which Alice should check. Timestamping is another way of preventing a replay attack. Synchronization should be achieved using a secure protocol. For example Bob periodically broadcasts the time on his clock together with a MAC. When Alice wants to send Bob a message, she includes her best estimate of the time on his clock in her message, which is also authenticated. Bob only accepts messages for which the timestamp is within a reasonable tolerance. The advantage of this scheme is that Bob does not need to generate (pseudo-) random numbers.

Resolution - The number of pixels per unit of area.  The greater the  number of pixels, the higher the resolution.

Resource - In project management terminology, resources are required to carry out the project tasks. They can be people, equipment, facilities, funding, or anything else capable of definition (usually other than labor) required for the completion of a project activity. The lack of a resource will therefore be a constraint on the completion of the project activity. Resources may be storable or non storable. Storable resources remain available unless depleted by usage, and may be replenished by project tasks which produce them. Non-storable resources must be renewed for each time period, even if not utilized in previous time periods. Resource scheduling, availability and optimization are considered key to successful project management.

RGB (red-Green-Blue) - A computer color display that provides a separate output of red, green, and blue signals, each of which can be controlled.  Typically, an RGB monitor offers a higher resolution than a composite monitor, in which the RGB signals are combined before output.

RIP - The Routing Information Protocol is one of the most commonly used Interior Gateway Protocol (IGP) routing protocols on internal networks (and to a lesser extent, networks connected to the Internet), which helps routers dynamically adapt to changes of network connections by communicating information about which networks each router can reach and how far away those networks are.  Although RIP is still actively used, it is generally considered to have been made obsolete by routing protocols such as OSPF and IS-IS. Nonetheless, a somewhat more capable protocol in the same basic family (distance-vector routing protocols), EIGRP, also sees some use.

Routing - In computer networking the term routing refers to selecting paths in a computer network along which to send data. Routing directs forwarding, the passing of logically addressed packets from their source toward their ultimate destination through intermediary nodes (called routers). The routing process usually directs forwarding on the basis of routing tables within the routers, which maintain a record of the best routes to various network destinations. Thus the construction of routing tables becomes very important for efficient routing. Routing differs from bridging in its assumption that address-structures imply the proximity of similar addresses within the network, thus allowing a single routing-table entry to represent the route to a group of addresses. Therefore, routing outperforms bridging in large networks, and it has become the dominant form of path-discovery on the Internet. Small networks may involve hand-configured routing tables. Large networks involve complex topologies and may change constantly, making the manual construction of routing tables very problematic. Nevertheless, most of the public switched telephone network (PSTN) uses pre-computed routing tables, with fallback routes if the most direct route becomes blocked. Dynamic routing attempts to solve this problem by constructing routing tables automatically, based on information carried by routing protocols, and allowing the network to act nearly autonomously in avoiding network failures and blockages. Dynamic routing dominates the Internet. However, the configuration of the routing protocols often requires a skilled touch; one should not suppose that networking technology has developed to the point of the complete automation of routing. Packet-switched networks, such as the Internet, split data up into packets, each labeled with the complete destination address and each routed individually. Circuit switched networks, such as the voice telephone network, also perform routing, in order to find paths for circuits (such as telephone calls) over which they can send large amounts of data without continually repeating the complete destination address. The hardware used in routing includes hubs, switches, and routers.  Dynamic routing uses one of two broad classes of routing algorithms, Distance vector algorithms and Link-state algorithms.  Distance vector algorithms use the Bellman-Ford algorithm. This approach assigns a number, the cost, to each of the links between each node in the network. Nodes will send information from point A to point B via the path that results in the lowest total cost (i.e. the sum of the costs of the links between the nodes used).  The algorithm operates in a very simple manner. When a node first starts, it only knows of its immediate neighbors, and the direct cost involved in reaching them. (This information, the list of destinations, the total cost to each, and the next hop to send data to get there, makes up the routing table, or distance table.) Each node, on a regular basis, sends to each neighbor its own current idea of the total cost to get to all the destinations it knows of. The neighboring node(s) examine this information, and compare it to what they already 'know'; anything which represents an improvement on what they already have, they insert in their own routing table(s). Over time, all the nodes in the network will discover the best next hop for all destinations, and the best total cost. When one of the nodes involved goes down, those nodes which used it as their next hop for certain destinations discard those entries, and create new routing-table information. They then pass this information to all adjacent nodes, which then repeat the process. Eventually all the nodes in the network receive the updated information, and will then discover new paths to all the destinations which they can still "reach".  Link-state Algorithms: When applying link-state algorithms, each node uses its fundamental data a map of the network in the form of a graph. To produce this, each node floods the entire network with information about what other nodes it can connect to, and each node then independently assembles this information into a map. Using this map, each router then independently determines the best route from itself to every other node. The algorithm used to do this, Dijkstra's algorithm, does this by building another data structure, a tree, with the current node itself as the root, and containing every other node in the network. It starts with a tree containing only itself. Then, one at a time, from the set of nodes which it has not yet added to the tree, it adds the node which has the lowest cost to reach an adjacent node which already appears in the tree. This continues until every node appears in the tree. This tree then serves to construct the routing table, giving the best next hop, etc, to get from the node itself to any other node in the network.  A routing metric consists of any value used by routing algorithms to determine whether one route should perform better than another. Metrics can cover such information as bandwidth, delay, hop count, path cost, load, MTU, reliability, and communication cost. The routing table stores only the best possible routes, while link-state or topological databases may store all other information as well.

RPC - A remote procedure call (RPC) is a protocol that allows a computer program running on one computer to cause a subroutine on another computer to be executed without the programmer explicitly coding the details for this interaction. When the software in question is written using object-oriented principles, RPC may be referred to as remote invocation or remote method invocation.  RPC is an easy and popular paradigm for implementing the client-server model of distributed computing. An RPC is initiated by the caller (client) sending a request message to a remote system (the server) to execute a certain procedure using arguments supplied. A result message is returned to the caller.

RTDBMS - In a Real-Time DataBase Management System (RTDBMS), transactions must not only maintain the consistency constraints of the database but also satisfy their timing constraints. In addition, a RTDBMS often involves processing both temporal and persistent data. A RTDBMS is appropriate for applications such as air traffic control, stock trading, telecommunications, flexible manufacturing and aircraft flight programs. Its main goal is to meet the timing constraints of data transactions regardless of system or transaction failures. Our research in this area aims at the development of techniques to manage concurrency control, nested transactions, real-time promising, and recovery.

RTOS - A Real-Time Operating System is a class of operating system intended for real-time applications. Examples include embedded applications (programmable thermostats, household appliance controllers, mobile telephones), industrial robots, industrial control (see SCADA), and scientific research equipment.  A RTOS facilitates the creation of a real-time system, but does not guarantee the finished product will be real-time; this requires correct development of the software. A RTOS does not necessarily have high throughput; rather, a RTOS provides facilities which, if used properly, guarantee that system deadlines can be met generally ("soft real-time") or deterministically ("hard real-time"). A RTOS will typically use specialized scheduling algorithms in order to provide the real-time developer with the tools necessary to produce deterministic behavior in the final system. A RTOS is valued more for how quickly and/or predictably it can respond to a particular event than for the given amount of work it can perform over time. Key factors in an RTOS are therefore minimal interrupt and thread switching latency.  An early example of a large-scale real-time operating system was the so-called "control program" developed by American Airlines and IBM for the Sabre Airline Reservations System.  Debate exists about what actually constitutes real-time computing.  There are two basic designs: 1-) An event-driven operating system only changes tasks when an event requires service. 2-) A time-sharing design switches tasks on a clock interrupt, as well as on events.

The time-sharing design switches tasks more often than is strictly necessary, but gives "smoother", more deterministic multitasking, the illusion that a user has sole use of a machine.

RTP - The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over the Internet. It was developed by the Audio-Video Transport Working Group of the IETF and first published in 1996 as RFC 1889.  It is frequently used in streaming media systems in conjunction with RTCP as well as videoconferencing and push to talk systems (in conjunction with H.323 or SIP), making it the technical foundation of the Voice over IP industry. It goes along with the RTCP and it's built on top of User Datagram Protocol.

RTCP - RTP Control Protocol is a sister protocol of the Real-time Transport Protocol (RTP). It is defined in RFC 3550 (which obsoletes RFC 1889).  RTCP stands for Real-time Transport Control Protocol, provides out-of-band control information for an RTP flow. It partners RTP in the delivery and packaging of multimedia data, but does not transport any data itself. It is used periodically to transmit control packets to participants in a streaming multimedia session. The primary function of RTCP is to provide feedback on the quality of service being provided by RTP.  RTCP is used for QoS reporting.

RUP - The Rational Unified Process is an iterative software development process created by the Rational Software Corporation, now a division of IBM. The RUP is not a single concrete prescriptive process, but rather an adaptable process framework. As such, RUP describes how to develop software effectively using proven techniques. While the RUP encompasses a large number of different activities, it is also intended to be tailored, in the sense of selecting the development processes appropriate to a particular software project or development organization. The RUP is recognized as particularly applicable to larger software development teams working on large projects. Rational Software offers a product (known below as the Rational Unified Process Product) that provides tools and technology for customizing and executing the process.  The static 4: 1-) Roles are who – a role is the behavior and responsibilities of a person or team, not the person themselves. 2-) Artifacts are what – they are the outcome of activities, including all the documents and models produced while working through the process. 3-) Workflow is when – it is a sequence of activities or the design of processes that must be completed. 4-) Activity is how – it is the actual tasks a worker performs.

This side of the process is called static because it describes how things are done. It is not dependent on the project at hand. For example, the description of the tasks and deliverables of a use-case designer is the same for each project.



SAP - Standard Accounting Program, similar in scope and usage to ERP.  SAP, started in 1972 by five former IBM employees in Mannheim, Germany, states that it is the world's largest inter-enterprise software company and the world's fourth-largest independent software supplier, overall. The original SAP idea was to provide customers with the ability to interact with a common corporate database for a comprehensive range of applications. Gradually, the applications have been assembled and today many corporations, including IBM and Microsoft, are using SAP products to run their own businesses.  SAP applications, built around their latest R/3 system, provide the capability to manage financial, asset, and cost accounting, production operations and materials, personnel, plants, and archived documents. The R/3 system runs on a number of platforms including Windows 2000 and uses the client/server model. The latest version of R/3 includes a comprehensive Internet-enabled package.  SAP has recently recast its product offerings under a comprehensive Web interface, called mySAP.com, and added new e-business applications, including Customer Relationship Management (CRM) and Supply Chain Management (SCM).  In early 2001, SAP, a publicly traded company, had 21,500 employees in over 50 countries, and more than 30,000 installations. SAP is turning its attention to small- and-medium sized businesses. A recent R/3 version was provided for IBM's AS/400 platform

SBC - A Session Border Controller is a device used in some VoIP networks. SBCs are put into the signaling and media path between calling and called party. The SBC acts as if it was the called VoIP phone and places a second call to the called party. The effect of this behavior is that not only the signaling traffic, but also the media traffic (voice, video etc) crosses the SBC. Without an SBC, the media traffic travels directly between the VoIP phones. Private SBCs are used along with firewalls to enable VoIP calls to and from a protected enterprise network. Public VoIP service providers use SBCs to allow the use of VoIP protocols from private networks with internet connections using NAT.  Additionally, some SBCs can also allow VoIP calls to be set up between two phones using different VoIP signaling protocols ( SIP, H.323, Megaco/MGCP, etc...) as well as performing transcoding of the media stream when different codecs are in use. Many SBCs also provide firewall features for VoIP traffic (denial of service protection, call filtering, bandwidth management, etc...).  In contrast to conventional phone systems, the OSI layers of a VoIP-based network need not to be operated by a single company. A VoIP user may purchase her internet access from one internet service provider and her VoIP service from a second company. Some telecom companies use SBCs to revert this characteristic in order to retain their current business model when offering public VoIP services.  The concept of the SBC is controversial to proponents of end-to-end systems and peer-to-peer networking.


SBCs can extend the length of the media path (the way of media packets through the network) significantly. A long media path is undesirable, as it increases the delay of voice packets (especially if the SBC implements transcoding) and the probability of packet loss. Both effects deteriorate the voice/video quality. Some SBCs can detect if the ends of the call are in the same subnetwork and release control of the media enabling it to flow directly between the clients, this is anti-tromboning.


SBCs break the end-to-end transparency. VoIP phones can't use new protocol features unless they are understood by the SBC. End-to-End encryption can't be used if the SBC does not have the key.


Far-end or hosted NAT traversal can be done without SBCs if the VoIP phones support protocols like STUN, TURN, ICE, or Universal Plug and Play (UPnP).

An SBC may provide session media (normally Real-time Transport Protocol) and signaling (normally SIP) wiretap services, which can be used by providers to enforce requests for the lawful interception of network sessions. Standards for the interception of such services are provided by CALEA and ETSI, among others.

Schedule - A schedule is a list of employees who are working on any given day, week, or month in a workplace. A schedule is necessary for the day-to-day operation of any retail store or manufacturing facility. The process of creating a schedule is called scheduling. An effective workplace schedule balances the needs of employees, tasks, and in some cases, customers. A daily schedule is usually ordered chronologically, which means the first employees working that day are listed at the top, followed by the employee who comes in next, et cetera. A weekly or monthly schedule is usually ordered alphabetically, employees being listed on the left hand side of a grid, with the days of the week on the top of the grid. A schedule is most often created by a manager. In larger operations, a Human Resources manager or specialist may be solely dedicated to writing the schedule. A schedule by this definition is sometimes referred to as workflow. In project management, a schedule consists of a list of a project's terminal elements with intended start and finish dates.  A Gantt chart can provide a graphical representation of a project schedule.  Critical chain project management warns that terminal-element start dates and finish dates function as random variables, and suggests managing a project not by its traditional schedule but rather by using buffer management and a relay race mentality.

SCM - Software Configuration Management is part of configuration management (CM). Roger Pressman, in his book, Software Engineering: A Practitioner's Approach, says that software configuration management (SCM) is a "set of activities designed to control change by identifying the work products that are likely to change, establishing relationships among them, defining mechanisms for managing different versions of these work products, controlling the changes imposed, and auditing and reporting on the changes made." In other words, SCM is a methodology to control and manage a software development project.

SCM - Supply chain management (SCM) deals with the planning and execution issues involved in managing a supply chain.  The components of SCM are:

bulletDemand planning (forecasting)
bulletDemand collaboration (collaborative resolution process to determine consensus forecasts)
bulletOrder promising (When one can promise a product to a customer taking into account lead times and constraints)
bulletStrategic network optimization (what plants and DC's should serve what markets for what products) (monthly - yearly)
bulletProduction and distribution planning (Coordinate the actual production and distribution plans for a whole enterprise) (daily)
bulletProduction scheduling (For a single location create a feasible production schedule) (minute by minute)
bulletTransportation planning (For multiple supply, manufacturer, distributor and warehousing points in a network)
bulletTransportation execution (Enactment of long term plans on a per shipment basis, typically performed by focused organizations called forwarders)
bulletTracking and Measuring (An ever increasing aspect of supply chain management designed to highlight potential against the plan and possible process improvements)
bulletPlan of reduction of costs and management of the performance (diagnosis of the potential and the indicators, the organization and planifiaction strategic, masters dysfunctions in real time, evaluation and accounting reporting, evaluation and reporting quality)

The SupplyChainDigest web site is very informative http://www.scdigest.com

SCTP - The Stream Control Transmission Protocol is a transport layer protocol defined in 2000 by the IETF Signaling Transport (SIGTRAN) working group. The protocol is defined in RFC 2960, and an introductory text is provided by RFC 3286. As a transport protocol, SCTP is equivalent in a sense to TCP or UDP. Indeed it provides some similar services as TCP — ensuring reliable, in-sequence transport of messages with congestion control. (In the absence of native SCTP support, it may sometimes be desirable to tunnel SCTP over UDP.  SCTP was originally intended for the transport of telephony (SS7) protocols over IP, with the goal of duplicating some of the reliability attributes of the SS7 signaling network in IP. This IETF effort is known as SIGTRAN. In the meantime, other uses have been proposed, for example the DIAMETER protocol and Reliable server pooling (RSerPool).  One of the key differences between TCP & SCTP is that TCP transports a byte-stream while SCTP is capable of transporting multiple message-streams. All bytes sent in a TCP connection must be delivered in that order, which requires that a byte transmitted first must safely arrive at the destination before a second byte can be processed even if the second byte manages to arrive first. If an arbitrary number of bytes are sent in one step and later some more bytes are sent, these bytes will be received in order, but the receiver can not distinguish which bytes were sent in which step. SCTP in contrast, conserves message boundaries by operating on whole messages instead of single bytes. That means if one message of several related bytes of information is sent in one step, exactly that message is received in one step.  Multi-streaming refers to the capability of SCTP to transmit several independent streams of messages in parallel. For example, transmitting two images in a HTTP application in parallel over the same SCTP association. You might think of multi-streaming as bundling several TCP-connections in one SCTP-association operating with messages instead of bytes.  TCP ensures the correct order of bytes in the stream by conceptually assigning a sequence number to each byte sent and ordering these bytes based on that sequence number when they arrive. SCTP, instead, assigns different sequence numbers on messages sent in a stream. This allows messages in different streams to be ordered independently. However, message ordering is optional in SCTP. If the user application so desires, messages will be processed in the order they are received instead of the order they were sent, should these differ.  Message-based delivery is one of the requirements for PSTN signaling. Multi-Streaming also is an advantage when used to transport Public Switched Telephone Networks Services. If an SCTP connection is set up to carry, say, ten phone calls with one call per stream, then if a single message is lost in only one phone call, the other nine calls will not be affected. To handle ten phone calls in TCP, some form of multiplexing would be required to put all ten phone calls into a single byte-stream. If a single packet for phone call #3 is lost then all packets after that could not be processed until the missing bytes are retransmitted, thus causing unnecessary delays in the other calls.

SDET - A Software Design Engineer in Test is a developer who designs, develops, and maintains automation systems and often expandable suites containing multiple automation programs to be used by the development and test teams. They are responsible for utilizing innovative test technologies to develop a product's testing strategy, and for facilitating the creation and execution of automated test suites across a diverse set of technologies. They look at source code for potential problems using Microsoft internal tools. They also reproduce, debug and isolate problems, and verify fixes.

SDLC - Systems Development Life Cycle, is defined by the United States Department of Justice as a software development process, although it is also a distinct process independent of software or other Information Technology considerations. It is used by a systems analyst to develop an information system, including requirements, validation, training, and user ownership through investigation, analysis, design, implementation, and maintenance. SDLC is also known as information systems development or application development. An SDLC should result in a high quality system that meets or exceeds customer expectations, within time and cost estimates, works effectively and efficiently in the current and planned information technology infrastructure, and is cheap to maintain and cost-effective to enhance. SDLC is a systems approach to problem solving and is made up of several phases, each comprised of multiple steps: The software concept - identifies and defines a need for the new system A requirements analysis - analyzes the information needs of the end users The architectural design - creates a blueprint for the design with the necessary specifications for the hardware, software, people and data resources Coding and debugging - creates and programs the final system System testing - evaluates the system's actual functionality in relation to expected or intended functionality. The six official phases are: 1-) Preliminary Investigation / Feasibility Study, 2-) Systems Analysis / Systems Requirements, 3-) Systems Design / Design Specifications, 4-) Systems Development, 5-) Systems Implementation, 6-) Systems Maintenance.

SDTV - Standard definition television is a digital television (DTV) format that provides a picture quality similar to digital versatile disk (DVD). SDTV and high definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions, which are becoming the standard. Because a compressed SDTV digital signal is smaller than a compressed HDTV signal, broadcasters can transmit up to five SDTV programs simultaneously instead of just one HDTV program. This is multicasting. Multicasting is an attractive feature because television stations can receive additional revenue from the additional advertising these extra programs provide. With today's analog television system, only one program at a time can be transmitted.

SDI - Serial Digital Interface.

SDL - Specification and Description Language.  SDL is a low level design language using flowcharts and text.  SDL is an International Telecommunications Union standard used to create object-oriented flowcharts that document the low level design of, and not limited to, communications and telecommunications systems networks.  SDL files can be used to generate source code as per specifications.

SECAM (Sequential Couleur Avec Memoire) - A color television format developed and used in France.  SECAM video is characterizes by 625 scan lines and 25 frames per second.

Self similar - A self-similar object is exactly or approximately similar to a part of itself. A curve is said to be self-similar if, for every piece of the curve, there is a smaller piece that is similar to it. For instance, a side of the Koch snowflake is self-similar; it can be divided into two halves, each of which is similar to the whole.  Many objects in the real world, such as coastlines, are statistically self-similar: parts of them show the same statistical properties at many scales. Self-similarity is a typical property of fractals.  It also has important consequences for the design of computer networks, as typical network traffic has self-similar properties. For example, in telecommunications traffic engineering, packet switched data traffic patterns seem to be statistically self-similar. This property means that simple models using a Poisson distribution are inaccurate, and networks designed without taking self-similarity into account are likely to function in unexpected ways.

Scan Doubling - The process of eliminating the visible video scan lines by doubling them and filling in the "blank" lines.

Security Mountable - Institutional Televisions are equipped with heavy-duty mounting blocks on the bottom of the cabinet for simple, secure mounting to ceiling, wall, or furniture brackets.

SIGTRAN - SIGTRAN is the name given to an IETF working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for SS7 and ISDN communications protocols. The most significant protocol defined by the SIGTRAN group was the Stream Control Transmission Protocol (SCTP), which is used to carry PSTN signaling over IP. The SIGTRAN group was significantly influenced by telecommunications engineers intent on using the new protocols for adapting VoIP networks to the PSTN with special regard to signaling applications. Recently, SCTP is finding applications beyond its original purpose wherever reliable datagram service is desired.

SIP - Session Initiation Protocol is a protocol developed by the IETF MMUSIC Working Group and proposed standard for initiating, modifying, and terminating an interactive user session that involves multimedia elements such as video, voice, instant messaging, online games, and virtual reality. In November 2000, SIP was accepted as a 3GPP signaling protocol and permanent element of the IMS architecture. It is one of the leading signaling protocols for Voice over IP, along with H.323.  SIP clients traditionally use TCP and UDP port 5060 to connect to SIP servers and other SIP endpoints. SIP is primarily used in setting up and tearing down voice or video calls. However, it can be used in any application where session initiation is a requirement. These include, Event Subscription and Notification, Terminal mobility and so on. There are a large number of SIP-related RFCs that define behavior for such applications. All voice/video communications are done over RTP.  A motivating goal for SIP was to provide a signaling and call setup protocol for IP-based communications that can support a superset of the call processing functions and features present in the PSTN. The SIP Protocol by itself does not define these features, rather, its focus is call-setup and signaling. However, it has been designed to enable the building of such features in network elements known as Proxy Servers and User Agents. As such these are features that permit familiar telephone-like operations: dialing a number, causing a phone to ring, hearing ringback tones or a busy signal. Implementation and terminology are different in the SIP world but to the end-user, the behavior is similar.  SIP enabled telephony networks can also implement many of the more advanced call processing features present in SS7. SIP works in concert with several other protocols and is only involved in the signaling portion of a communication session. SIP acts as a carrier for the Session Description Protocol (SDP), which describes the media content of the session, e.g. what IP ports to use, the codec being used etc. In typical use, SIP "sessions" are simply packet streams of the Real-time Transport Protocol (RTP). RTP is the carrier for the actual voice or video content itself.

Siren14 - Polycom’s patented Siren14 algorithm offers breakthrough benefits compared to earlier wideband audio technology. Siren14 delivers low-latency 14 kHz super-wideband audio at nearly half the bit rate of the alternative MPEG4 AAC-LD codec, while requiring one-tenth to one-twentieth of the computing power.

Six Sigma - stands for Six Standard Deviations (Sigma is the Greek letter used to represent standard deviation in statistics) from mean. Six Sigma methodology provides the techniques and tools to improve the capability and reduce the defects in any process.  It was started in Motorola, in its manufacturing division,  where millions of parts are made using the same process repeatedly. Eventually Six Sigma evolved and applied to other non manufacturing processes. Today you can apply Six Sigma to many fields such as Services, Medical and Insurance Procedures, Call Centers.  Six Sigma methodology improves any existing business process by constantly reviewing and re-tuning the process.  To achieve this, Six Sigma uses a methodology known as DMAIC (Define opportunities, Measure performance, Analyze opportunity, Improve performance, Control performance).  Six Sigma methodology can also be used to create a brand new business process from ground up using DFSS (Design For Six Sigma) principles. Six Sigma Strives for perfection. It allows for only 3.4 defects per million opportunities for each product or service transaction. Six Sigma relies heavily on statistical techniques to reduce defects and measure quality. Six Sigma experts (Green Belts and Black Belts) evaluate a business process and determine ways to improve upon the existing process. Six Sigma experts can also design a brand new business process using DFSS (Design For Six Sigma) principles. Typically its easier to define a new process with DFSS principles than refining an existing process to reduce the defects.  Six Sigma incorporates the  basic principles and techniques used in Business, Statistics, and Engineering. These three form the core elements of Six Sigma. Six Sigma improves the process performance, decreases variation and maintains consistent quality of the process output. This leads to defect reduction and improvement in profits, product quality and customer satisfaction.

Six Sigma methodology is also used in many Business Process Management initiatives these days. These Business Process Management initiatives are not necessarily related to manufacturing. Many of the BPM's that use Six Sigma in today's world include call centers, customer support, supply chain management and project management.

SKU - Stock Keeping Unit.

SLA - Service Level Agreement.  SLA is a formal written agreement made between two parties: the service provider and the service recipient. The SLA itself defines the basis of understanding between the two parties for delivery of the service itself. The document can be quite complex, and sometimes underpins a formal contract. The contents will vary according to the nature of the service itself, but usually includes a number of core elements, or clauses.  Generally, an SLA should contain clauses that define a specified level of service, support options, incentive awards for service levels exceeded and/or penalty provisions for services not provided. Before having such agreements with customers the IT services need to have a good quality of these services, Quality management will try to improve the QoS, whereas the SLAs will try to keep the quality and guarantee the quality to the customer.

SmartCard TelevisionTM - This patented technology has already become an industry standard featuring an integrated expansion slot on the back of each SmartCard TelevisionTM where a SmartCard module can easily be inserted, upgrading the capabilities to fulfill virtually any professional application.

Smart Loader Clone Programming Device: RL5180CK (normally not included) - Used to clone program multiple sets, simply plug the Smart Loader into the addressable interface port and follow simple onscreen menus to download programming settings. Smart Loader is then used to upload the information into additional sets.

SmartMuteTM - Automatically displays Closed Caption service whenever the user activates the Mute function.

Smart PlugTM Two-Way Addressable Port - Hospitality Televisions feature the unique Smart PlugTM on the back which allows for simple, two-way communication between the set and a remote source, such as a computer or a rack of equipment with a VCR, DVD player, etc.

SmartSoundTM - Maintains constant volume levels when changing channels or programs, automatically pulling high-level sound down by 6dB and raising low-level sound by 3dB.

SMS - Short Messaging Service (SMS) is available on many 2G and all 3G wireless networks. With SMS, subscribers can send short text messages (usually about 160 characters) to and from wireless handsets. Enhancements are made to support rich text and graphics.

SOAP - SOAP is a protocol for exchanging XML-based messages over a computer network, normally using HTTP and also SMTP. SOAP forms the foundation layer of the web services stack, providing a basic messaging framework that more abstract layers can build on. SOAP can be used to facilitate a Service-Oriented architectural pattern.  There are several different types of messaging patterns in SOAP, but by far the most common is the Remote Procedure Call (RPC) pattern, where one network node (the client) sends a request message to another node (the server), and the server immediately sends a response message to the client. Indeed, SOAP is the successor of XML RPC.

SONET - see Synchronous Optical Networking.

Special Setup Remote Transmitter: RG4172BK (normally not included) - Used during initial setup of televisions, the setup remote allows access to critical TV functions such as power, channel up/down, volume, color, tint, brightness, sharpness, etc. Once setup is complete, the setup transmitter is retained in a secure location.

Spill-Resistant Cabinet - Reduces the risk of damage to the television in the event liquid is spilled on the cabinet.

Spoofing Attack - in computer security terms, refers to a situation in which one person or program is able to masquerade successfully as another.  An example from cryptography is the man in the middle attack, in which an attacker spoofs Kristen into believing he's Frank, and spoofs Frank into believing he's Kristen, thus gaining access to all messages in both directions without the trouble of any cryptanalytic effort.  The attacker must monitor the packets sent from Kristen to Frank and then guess the sequence number of the packets. Then the attacker knocks out Kristen with a SYN attack and injects his own packets, claiming to have the address of Kristen. Kristen's firewall can defend against spoof attacks when it has been configured with knowledge of all the IP addresses connected to each of its interfaces. It can then detect a spoofed packet if it arrives from an interface that is not known to be connected to that interface.  Many carelessly designed protocols are subject to spoof attacks, including many of those used on the Internet.

Another kind of spoofing is "web page spoofing," also known as phishing. In this attack, a web page is reproduced in "look and feel" to another server but is owned and operated by someone else. It is intended to fool someone into thinking that they are connected to a trusted site. Typically, a bank's log-in page might be spoofed by a crook. The crook then harvests the user names and passwords. This attack is often performed with the aid of DNS cache poisoning in order to direct the user away from the legitimate site and into the false one. Once the user puts in their password, the attack-code reports a password error, then redirects the user back to the legitimate site. 

Referrer Spoofing: Some websites, especially pornographic paysites, allow access to their materials only from certain approved (login-) pages. This is enforced by checking the Referrer header of the HTTP request. This referrer header however can be changed (known as "Referrer spoofing" or "Ref-tar spoofing"), allowing users to gain unauthorized access to the materials.

"Spoofing" can also refer to copyright holders placing distorted or un-listenable versions of works on file-sharing networks, to discourage downloading from these sources. An example of this is the spoof of Madonna's album American Life.

Spyware - In the field of computing, the term spyware refers to a broad category of malicious software designed to intercept or take partial control of a computer's operation without the informed consent of that machine's owner or legitimate user. While the term taken literally suggests software that surreptitiously monitors the user, it has come to refer more broadly to software that subverts the computer's operation for the benefit of a third party. Spyware differs from viruses and worms in that it does not usually self-replicate. Like many recent viruses, however, spyware – by design – exploits infected computers for commercial gain. Typical tactics furthering this goal include delivery of unsolicited pop-up advertisements; theft of personal information (including financial information such as credit card numbers); monitoring of Web-browsing activity for marketing purposes; or routing of HTTP requests to advertising sites. As of 2005, spyware has become one of the pre-eminent security threats to computer-systems running Microsoft Windows operating-systems (and especially to users of Internet Explorer because of that browser's collaboration with the Windows operating system). Some malware on the Linux and Mac OS X platforms has behavior similar to Windows spyware, but to date has not become anywhere near as widespread due to their comparatively smaller user base.

SRTP - Secure Real-time Transport Protocol defines a profile of RTP, intended to provide encryption, message authentication and integrity, and replay protection to the RTP data in both unicast and multicast applications. It was developed by David Oran (Cisco) and Rolf Blom (Ericsson) and first published by IETF in March 2004 as RFC 3711.  Since RTP is closely related to RTCP which can be used to control the RTP session.

SRTCP - Secure RTCP is a sister protocol to SRTP.  SRTCP provides the same security-related features to RTCP, as ones provided by SRTP to RTP.  Utilization of SRTP or SRTCP is optional to utilization of RTP or RTCP; but even if SRTP/SRTCP are used, all provided features (such as encryption and authentication) are optional and can be separately enabled or disabled. The only exclusion is message authentication feature which is indispensably required the for using SRTCP.

SRV Record - An SRV record or Service record is a category of data in the Internet Domain Name System specifying information on available services. It is defined in RFC 2782. Newer internet protocols such as SIP and XMPP often require SRV support from clients. Client implementations of older protocols (e.g. LDAP, SMTP) may have SRV support added to it.  An SRV record holds the following information:

bulletService: the symbolic name of the desired service.
bulletProtocol: this is usually either TCP or UDP.
bulletDomain name: the domain for which this record is valid.
bulletTTL: standard DNS time to live field.
bulletClass: standard DNS class field (this is always IN).
bulletPriority: the priority of the target host.
bulletWeight: A relative weight for records with the same priority.
bulletPort: the TCP or UDP port on which the service is to be found.
bulletTarget: the hostname of the machine providing the service.
An example SRV record: _sip._tcp.example.com 86400 IN SRV 0 5 5060 sipserver.example.com. 

SRV record is also used for load balancing: The priority field is similar to an MX record's priority value. Clients always use the SRV record with the lowest priority value first, and only fall back to other records if the connection with this record's host fails. Thus a service may have a designated "fallback" server, which will only be used if the primary server fails. Only another SRV record, with a priority field value higher than the primary server's record, is needed.

SS7 - Signaling System 7 (SS7) is the protocol used in the public switched telephone system for setting up calls and providing services such as tollfree numbers, call forwarding, caller ID and local number portability.

Stereo Sound System - The built-in stereo sound system incorporates an MTS decoder for reception and reproduction of broadcast stereo television programs (where available).

Stereo Sound System with dbx® Noise Reduction - Built-in stereo sound system includes MTS/SAP decoder and dbx® noise reduction to eliminate hiss and high-frequency interference and add impact to your classroom programs.

Streaming media - Sending video or audio over a network as needed, such as Real Audio/Video or Microsoft NetShow, instead of forcing the user to download the entire file before viewing it. Typically a few seconds of data is sent ahead and buffered in case of network transmission delays. (Although some data is buffered to the hard drive, it is written to temporary storage and is gone once viewing is complete.)

Student Syndrome - In project management terminology, Student Syndrome refers to the phenomenon that many people will start to fully apply themselves to a task just in the wake of a deadline. This leads to wasting any buffers built into individual task duration estimates.

Super VGA - A term used to denote higher than VGA (640 x 480) resolution. Most Super VGA computers/cards output resolutions up to 1280 x 1024 and 16 million colors.

SVGA/VGA Input with Loop-Through Output - Typical SVGA or VGA cables with D-shell connectors are the only additional hardware required for hookup to a PC. Use the same cabling setup with a VGA/Mac¨ adaptor and a SmartCard TelevisionTM will accept most Mac® inputs. This port allows display of computer-generated data, graphic images, animated models, or full-motion video with real-time keyboard interactivity and display resolutions of 640 x 480, 800 x 600, or 1024 x 768. Compatible with most PC and Mac® refresh rates, the SCN3NFN module offers excellent performance from 50-75Hz.

S-Video - Composite video signal separated into the luminance (black & white) and chrominance (color), resulting in greater picture definition and superior definition.

S-Video Input - A standard S-Video input simplifies connection to any S-VHS VCR/camcorder, Web browser, or DVD player for the highest quality video images possible.

S-Video Input/Output w/Loop-Thru Capability - Allows connection of high resolution sources such as DVD, Web Browser or Laser Disc for maximum picture quality. Additionally, the ProKit1 features separate audio inputs and outputs dedicated to the S-Video signal. Loop-through capability allows one video source to be looped to multiple sets.

Success Factors - During the inception phase of a RUP project, the key stakeholders should establish criteria by which the project can be judged to have succeeded. These factors may include problems being solved, financial or other performance targets to be achieved. Where the factor is a fuzzy one (such as users being happy), this should be expressed in measurable terms. A good success factor should always be testable, and normally, UAT should be based on success criteria.

SYN Attacks - or SYN flood is a form of denial-of-service attack in which an attacker sends a succession of SYN requests to a target's system.  When a client attempts to start a TCP connection to a server, the client and server exchange a series of messages which normally runs like this: 1-) The client requests a connection by sending a SYN (synchronize) message to the server. 2-) The server acknowledges this request by sending SYN-ACK back to the client, which, 3-) Responds with an ACK, and the connection is established.  This is called the TCP three-way handshake, and is the foundation for every connection established using TCP/IP protocols.  A malicious client can skip sending this last ACK message. The server will wait for this bit for some time, as simple network congestion could also be the cause of the missing ACK.  If this so called half-open connection binds resources on the server or the server software is licensed per-connection, as is the case in many operating systems, it may be possible to take up all these resources or run out of Client Access Licenses by flooding the server with SYN messages. Once all resources CALs set aside for half-open connections are reserved, no new connections (legitimate or not) can be made, resulting in denial of service. Some systems may malfunction badly or even crash if other operating system functions are starved of resources this way.  Countermeasures include SYN cookies or limiting the number of new connections from a source per timeframe.

Sync - In video, a means of synchronizing signals with timing pulses to insure that each step in a process occurs at exactly the right time. For example: Horizontal Sync determines exactly when to begin each horizontal line (sweep) of the electron beam. Vertical Sync determines when to bring the electron beam to the top-left of the screen to start a new field. There are many other types of sync in a video system. (Also called Sync Signal or Sync Pulse.)

Synchronous Optical Networking - commonly known as SONET, is a standard for communicating digital information over optical fiber. It was developed to replace the PDH system for transporting large amounts of telephone and data traffic. It is defined by GR-253-CORE from Telcordia.  The more recent Synchronous Digital Hierarchy (SDH) standard is built on experience in the development of SONET. Both SDH and SONET are widely used today; SONET in the U.S. and Canada, SDH in the rest of the world. SDH is growing in popularity and is currently the main concern with SONET now being considered as the variation.  SONET differs from PDH in that the exact rates that are used to transport the data are tightly synchronized to network based clocks. Thus the entire network operates synchronously. SDH was made possible by the existence of atomic clocks.  Both SONET and SDH can be used to encapsulate earlier digital transmission standards, such as the PDH standard, or used directly to support either ATM or so-called Packet over SONET networking.  The basic SONET signal operates at 51.840 Mbit/s and is designated STS-1 (Synchronous Transport Signal one). The STS-1 frame is the basic unit of transmission in SONET.  The Synchronous Transport Module level 1 (STM-1) is the basic signal rate of SDH.
SONET/SDH Designations and bandwidths
Optical Carrier Level Frame Format SDH Level Frame Format Line Rate (kbit/s)
OC-1 STS-1 - - 51 840
OC-3 STS-3 SDH-1 STM-1 155 520
OC-9 STS-9 - - 466 560
OC-12 STS-12 SDH-4 STM-4 622 080
OC-18 STS-18 - - 933 120
OC-24 STS-24 SDH-8 STM-8 1 244 160
OC-36 STS-36 SDH-12 STM-12 1 866 240
OC-48 STS-48 SDH-16 STM-16 2 488 320
OC-96 STS-96 SDH-32 STM-32 4 976 640
OC-192 STS-192 SDH-64 STM-64 9 953 280
OC-256 STS-256 - - 13 271 040
OC-384 STS-384 - STM-128 19 906 560
OC-768 STS-768 - STM-256 39 813 120
OC-1536 STS-1536 - STM-512 79 626 240
OC-3072 STS-3072 - STM-1024 159 252 480

System Television Control - Transmit live or pre-recorded media, control the power, adjust settings and even lockout local control for individual TVs, select groups to all TVs in the network.



T1 (also known as DS1) - A leased T1 line, marketed and serviced by LECs, that provides 1.544 Mbps data rate (in N. America; the European E1 provides 2.048 Mbps). T1 is available almost everywhere, and can be fractionated. Fractional T1 services are less expensive than full T1. Typical interactive video-mediated telemedicine programs transmit video images at "1/4 T1" rates (384 Kbps).

T3 (also know as DS3) - A carrier of 45 Mbps bandwidth. One T3 channel can carry 28 T1 channels. Transmission of both voice and data digital signals at speeds of 44.736 Mbps and higher.

T.120 - T.120 is an ITU-T standard (International Telecommunications Union) for document conferencing. Document conferencing allows two or more people to concurrently view and edit a document across a network.  T.120 is the commonly used name to refer to a family of distinct standards. Many video conferencing companies were developing their own implementations of this until Microsoft released its free NetMeeting software. Now, many companies are using NetMeeting, while perhaps enhancing it in some way.

Tamper-Proof Setup - Institutional Televisions are designed to provide central control over the programming features of each set.  You can adjust all the things you'd expect-picture level, brightness, color, tint, sharpness, as well as set up the professional features that customize the unit exclusively for its intended purpose via remote programming. To prevent users from tampering with the controls or changing the programming you've worked so hard to customize, the Limited Function Remote will give end users access to the basics-on/off, channel and volume control, etc.

TDMA - Time Division Multiple Access is a technology for shared medium (usually radio) networks. It allows several users to share the same frequency by dividing it into different time slots. The users transmit in rapid succession, one after the other, each using their own timeslot. This allows multiple users to share the same transmission medium (e.g. radio frequency) whilst using only the part of its bandwidth they require. Used in the GSM, PDC and iDEN digital cellular standards, among others.  GSM, TDMA, iDEN, PDC and PHS are all based on dividing a radio channel into time slots. Each time slot can handle one call. These technologies differ in radio channel sizes and the number of time slots.  TDMA is also used extensively in satellite systems, LANs, physical security systems, and combat-net radio systems.

TDMoIP - takes advantage of the concept of bundling conversations that are heading to the same destination and wrapping them up inside the same packets. These can offer near toll quality audio in a 6-7 kbit/s data stream.

Telecine - A film-to-videotape transfer technique that rectifies the respective color frame rate differences between film and video.

Teleconferencing - Two or more people who are geographically distant having a meeting of some sort across a telecommunications link. Includes audio conferencing, video conferencing, and or data conferencing.

Telemedicine - The investigation and monitoring of patients and the education of patients and staff using systems which allow ready access to expert advice and patient information, no matter where the patient or the relevant information is located. The three main dimensions of telemedicine are health service, telecommunications, and medical computer science.

Telementoring - Interaction between medical personnel of different training levels- i.e. GMO and Pulmonologist, Physician's Assistant and Emergency Physician, Medic and Battalion Surgeon. The use of audio, video, and other telecommunications and electronic information processing technologies to provide individual guidance or instruction, for example, involving a consultant guiding a distant clinician in a new medical procedure. Tele-monitoring The use of audio, video, and other telecommunications and electronic information processing technologies to monitor patient status at a distance.

Telenursing - The use of telecommunications for nursing care.

Telepresence - The use of robotic and other devices that allow a person (e.g., a surgeon) to perform a task at a remote site by manipulation instruments (e.g., lasers or dental hand pieces) and receiving sensory information or feedback e.g., pressure akin to that created by touching a patient) that creates a sense of being present at the remote site and allows a satisfactory degree of technical performance (e.g., dexterity).

Terminal Element - a terminal element is the lowest element (activity or deliverable) in a work breakdown structure(WBS); it is not further subdivided.  Terminal elements are the items that are estimated in terms of resource requirements, budget and duration, linked by dependencies and scheduled.

Terminal End Station - A terminal end station is the client endpoint that provides real-time, two-way communications. This is often shortened to just terminal.

THIG - Topology Hiding Interface Gateway. 

Thread - A thread in computer science is short for a thread of execution. Threads are a way for a program to split itself into two or more simultaneously running tasks. (The name "thread" is by analogy with the way that a number of threads are interwoven to make a piece of fabric). Multiple threads can be executed in parallel on many computer systems. This multithreading generally occurs by time slicing (where a single processor switches between different threads) or by multiprocessing (where threads are executed on separate processors). Threads are similar to processes, but differ in the way that they share resources. Many modern operating systems directly support both time-sliced and multiprocessor threading with a process scheduler. The operating system kernel allows programmers to manipulate threads via the system call interface. Some implementations are called kernel threads, whereas lightweight processes is a specific type of kernel threads that share the same states and information. Absent that, programs can still implement threading by using timers, signals, or other methods to interrupt their own execution and hence perform a sort of ad hoc time-slicing. These are sometimes called user-space threads. An unrelated use of the term thread is for threaded code, which is a form of code consisting entirely of subroutine calls, written without the subroutine call instruction, and processed by an interpreter or the CPU. Two threaded code languages are Forth and early B programming languages.

Three-Prong Power Cord - Designed for the most demanding environments, this product is perfect for applications that require compliance with strict A/V electrical requirements.

Three-tier Architecture - In computing, Three-tier is a client-server architecture in which the user interface, functional process logic ("business rules"), data storage and data access are developed and maintained as independent modules, most often on separate platforms. The term "three-tier" or "three-layer", as well as the concept of multitier architectures, seems to have originated within Rational Software. The three-tier model is considered to be a software architecture and a software design pattern.  Apart from the usual advantages of modular software with well defined interfaces, the three-tier architecture is intended to allow any of the three tiers to be upgraded or replaced independently as requirements or technology change. For example, a change of operating system from Microsoft Windows to Unix would only affect the user interface code. Typically, the user interface runs on a desktop PC or workstation and uses a standard GUI, functional process logic may consist of one or more separate modules running on a workstation or application server, and an RDBMS on a database server or mainframe contains the data storage logic. The middle tier may be multi-tiered itself (in which case the overall architecture is called an "n-tier architecture").  It seems similar, although defined in slightly different terms, to the Model-view-controller concept and the pipes and filters concept.  Web services usage: In the Web service field, normally three-tier is used to refer to Websites, often Electronic commerce websites, which are built using three tiers:

  1. A front end Web server serving static content
  2. A middle dynamic content processing and generation level Application server, for example Java EE platform.
  3. A back end Database, comprising both data sets and the Database management system or RDBMS software that manages and provides access to the data.

Throughput - The amount of data transferred from one place to another or processed in a specified amount of time. Data transfer rates for disk drives and networks are measured in terms of throughput. Typically, throughputs are measured in kbps, Mbps and Gbps.

Tier 1 Carrier - A Tier 1 carrier is a telco or ISP that is at the top of the telecommunications tier.  Although there is no formal definition, the following statements generally hold: 1-) Tier 1 operators have operations in more than one country. 2-) Tier 1 operators own and operate their own physical networks, and either own or have IRU's on their international submarine cable links. 3-) Tier 1 operators have revenue-neutral or settlement-free peering agreements with other tier 1 operators in the same market.  Furthermore, it is widely accepted rule of thumb that Tier 1 operators do not pay for transit.  A given Tier 1 operator might only be considered tier 1 in a particular market or markets (typically a country or geographical area). For example, Reliance Infocom is undeniably tier 1 in India, but much too small to peer neutrally with Tier 1 operators in the United States and Europe.

TISPAN - The Telecoms & Internet converged Services & Protocols for Advanced Networks, formerly Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON) is a standardization body of ETSI, specialized in fixed networks and Internet convergence.  TISPAN’s release 1 architecture is based upon the 3GPP IMS Release 6 and 3GPP2 Revision A architectures. However, TISPAN has adopted a more generalized model able to address a wider variety of network and service requirements. This overall architecture is based upon the concept of cooperating subsystems sharing common components. This subsystem-oriented architecture enables the addition of new subsystems over the time to cover new demands and service classes. It also ensures that the network resources, applications, and user equipment (mostly inherited from IMS where possible) are common to all subsystems and therefore ensure user, terminal and service mobility to the fullest extent possible, including across administrative boundaries.

TMSI - The Temporary Mobile Subscriber Identity is the identity that is most commonly sent between the mobile and the network. It is a randomly allocated number that is given to the mobile, the moment it is switched on. The number is local to a location area, and so it has to be updated, each time the mobile moves to a new geographical area. The network can also change the TMSI of the mobile at any time. And it normally does so, in order to avoid the subscriber from being identified, and tracked by eavesdroppers on the radio interface. This makes it difficult to trace which mobile is which, except briefly, when the mobile is just switched on, or when the data in the mobile becomes invalid for one reason or another. At that point, the global "international mobile subscriber identity" (IMSI) must be sent to the network. This is a unique number that is associated with all GSM and UMTS network mobile phone users. The number is stored in the SIM card. The IMSI is sent as rarely as possible, to avoid it being identified and tracked. A key use of the TMSI is in paging a mobile. "Paging" is the one-to-one communication between the mobile and the base station. The most important use of broadcast information is to set up channels for "paging". Every cellular system has a broadcast mechanism to distribute such information to a plurality of mobiles.

Total Control -TVs that are designed to give you control over the programming features of each set, and control end user access to your programming.  In addition, Front Control Lockout locks all front controls, preventing anyone from changing the volume, channel or other television settings.

Traffic Engineering - Traffic engineering uses statistical techniques such as queuing theory to predict and engineer the behavior of telecommunications networks such as telephone networks or the Internet.  The field was created by the work of A. K. Erlang in whose honor the unit of telecommunication traffic intensity, the Erlang is named. The derived unit of traffic volume also incorporates his name. His Erlang distributions are still in common use in telephone traffic engineering.  The crucial observation in traffic engineering is that in large systems the law of large numbers can be used to make the aggregate properties of a system over a long period of time much more predictable than the behavior of individual parts of the system.  The queuing theory originally developed for circuit-switched networks is applicable to packet-switched networks.  The most notable difference between these sub-fields is that packet-switched data traffic is self-similar. This is a consequence of the calls being between computers, and not people.

Traffic Volume - In telecommunication networks, traffic volume is a measure of the total work done by a resource or facility, normally over 24 hours, and is measured in units of Erlang-hours. It is defined as the product of the average traffic intensity (in Erlang) and the period of study (in hours).  A traffic volume of one Erlang-hour can be caused by two circuits being occupied continuously for half an hour or by a circuit being half occupied (0.5 Erlang) for a period of two hours. Telecommunication operators are vitally interested in traffic volume, as it directly dictates their revenue.

Transcoder - A device that does transcoding. See below.

Transcoding - Converting a data stream from one format to another, such as MPEG 1 to H.263, or an H.320 videoconferencing session to H.323.

Truespeech - Truespeech is a codec used for low bandwidth encoding of speech (not music). It was created by the DSP Group. It is available on Microsoft Windows 98 among other systems.

Turn-key system - A Telecommunications system in which all components and installation services needed for operational teleconferencing have been provided by a single vendor or contractor.

Two-Way Communications - Transmitter and receiver on different frequencies allows two-way communication for example between the computer head-end and individual TVs in the network for monitoring, function controls and event scheduling.



UAT - User Acceptance Testing

UAV - Unmanned Aerial Vehicle

UGV - Unmanned Ground Vehicle

UMA - Unlicensed Mobile Access technology provides access to GSM and GPRS mobile services over unlicensed spectrum technologies, including Bluetooth and 802.11. By deploying UMA technology, service providers can enable subscribers to roam and handover between cellular networks and public and private unlicensed wireless networks using dual-mode mobile handsets. With UMA, subscribers receive a consistent user experience for their mobile voice and data services as they transition between networks. UMA technology characteristics:  1-) Seamless delivery of mobile voice and data services over unlicensed wireless networks. 2-) Provides the same mobile identity on Cellular RAN and unlicensed wireless networks. 3-) Seamless transitions (roaming and handover) between Cellular RAN and unlicensed wireless networks. 4-) Preserves investment in existing/future mobile core network infrastructure.  5-) Independent of underlying unlicensed spectrum technology (e.g. WiFi™, Bluetooth™).  6-)Transparent to existing, standard CPE devices (e.g. access points, routers and modems).  7-)Utilizes standard “always on" broadband IP access networks (e.g. DSL, Cable, T1/E1, Broadband Wireless, FTTH …).  8-)Security equivalent to current GSM mobile networks.  9-) No impact to operations of Cellular RAN (e.g. spectrum engineering, cell planning,…)

UML - Unified Modeling Language.  UML is a powerful tool for developers to use when working on object-oriented systems. Because its purpose is to document and model a software system using a language-independent methodology, software designers can more easily communicate their designs to other designers and to those who ultimately implement the software.  From a UML model an SDL design can be generated. The SW design engineer can either use a tool (e.g. Telelogic' SDT) to generate the actual code, or handover the SDL design to an experienced coder to generate the code as per the low level design SDL specifications.

UMTS - Universal Mobile Telecommunications System (UMTS) is a part of the International Telecommunications Union’s IMT-2000 vision of a global family of third-generation (3G) mobile communications systems. This version of 3G is a W-CDMA (Wideband-CDMA) technology being developed primarily by the European and Japanese. UMTS is the 3G technology designed to succeed GSM networks worldwide.  UMTS combines the W-CDMA air interface, GSM's Mobile Application Part (MAP) core, and the GSM family of speech codecs.  UMTS standard are 1885-2025 MHz for uplink and 2110-2200 MHz for downlink.  A major difference of UMTS compared to GSM is the air interface forming Generic Radio Access Network (GRAN). It can be connected to various backbone networks like the Internet, ISDN, GSM or to a UMTS network. GRAN includes the three lowest layers of OSI model. The network layer (OSI L3) protocols form the Radio Resource Management protocol (RRM). They manage the bearer channels between the mobile terminals and the fixed network including the handovers.  There are other competing 3G standards, such as CDMA2000 and systems including iBurst from Arraycom, Flarion and wCDMA-TDD (IPWireless).  Both CDMA2000 and W-CDMA are accepted by ITU as part of the IMT-2000 family of 3G standards, in addition to Enhanced Data Rates for Global Evolution (EDGE) and China's own 3G standard, TD-SCDMA. 

The UMTS spectrum allocated by ITU is already used in North America. The 1900 MHz range is used for 2G (PCS) services, and 2100 MHz range is used for satellite communications. Regulators are trying to free up the 2100 MHz range for 3G services, though UMTS in North America will still have to share spectrum with existing 2G services in the 1900 MHz band. 2G GSM services elsewhere use 900 MHz and 1800 MHz and therefore do not share any spectrum with planned UMTS services.  Until regulators allocate new spectrum specifically for 3G, there will be no firm answer to what frequencies UMTS will operate on in North America. AT&T Wireless launched UMTS services in the United States by the end of 2004 strictly using the existing 1900 MHz spectrum allocated for 2G PCS services. Cingular acquired AT&T Wireless in 2004 and has since then launched UMTS in select US cities. Initial rollout of UMTS in Canada will also be handled exclusively by the 1900 MHz band.

Unicast - Sending each user their own copy of a video (or other data) stream. As opposed to Multicast, where one copy is sent and whoever wants it listens to that copy.

Underscan - A decreasing of the raster size (H & V) so that four edges of the picture are visible on the screen. Underscanning allows viewing of skew and tracking which would not be visible in normal (overscanned) mode. It is also helpful when aligning test charts to be certain they touch all four corners of the raster. Likewise, when checking the alignment of multiplexer images from a film chain, underscan allows proper framing of the projected image going into the video camera.

URI - A Uniform Resource Identifier is an Internet protocol element consisting of a short string of characters that conform to a certain syntax. The string comprises a name or address that can be used to refer to a resource. It is a fundamental component of the World Wide Web.  A URI can be classified as a locator or a name or both. A Uniform Resource Locator (URL) is a URI that, in addition to identifying a resource, provides means of acting upon or obtaining a representation of the resource by describing its primary access mechanism or network "location". For example, the URL http://www.atksi.com/ is a URI that identifies a resource (ATKSI's home page) and implies that a representation of that resource (such as the home page's current HTML code, as encoded characters) is obtainable via HTTP from a network host named www.atksi.com. A Uniform Resource Name (URN) is a URI that identifies a resource by name in a particular namespace. A URN can be used to talk about a resource without implying its location or how to dereference it. For example, the URN urn:ISBN 0-123-45678-9 is a URI that, like an International Standard Book Number (ISBN), allows one to talk about a book, but doesn't suggest where and how to obtain an actual copy of it. The contemporary point of view among the working group that oversees URIs is that the terms URL and URN are context-dependent aspects of URI and rarely need to be distinguished. Furthermore, the term URL is increasingly becoming obsolete, as it is rarely necessary to differentiate between URLs and URIs, in general. The term web address has also replaced URL in terms of popular usage.  The URI syntax is essentially a URI scheme name like "http", "ftp", "mailto", "urn", etc., followed by a colon character, and then a scheme-specific part. The syntax and semantics of the scheme-specific part are determined by the specifications that govern the schemes, although the URI syntax does force all schemes to adhere to a certain general syntax that, among other things, reserves certain characters for special purposes, without always saying what those purposes are. The URI syntax also enforces restrictions on the scheme-specific part, in order to, for example, provide for a degree of consistency when the part has a hierarchical structure. Percent-encoding is an often misunderstood aspect of URI syntax.  An example URI: http://somehost/absolute/URI/with/absolute/path/to/resource.txt

User Agent - A user agent is the client application used with a particular network protocol; the phrase is most commonly used in reference to those which access the World Wide Web. Web user agents range from web browsers to search engine crawlers ("spiders"), as well as mobile phones, screen readers and Braille browsers used by people with disabilities. When Internet users visit a web site, a text string is generally sent to identify the user agent to the server. This forms part of the HTTP request, prefixed with User-agent: or User-Agent: and typically includes information such as the application name, version, host operating system, and language. Bots, such as web crawlers, often also include a URL and/or e-mail address so that the webmaster can contact the operator of the bot. The user-agent string is one of the criteria by which crawlers can be excluded from certain pages or parts of a website using the "Robots Exclusion Standard" (robots.txt). This allows webmasters who feel that certain parts of their website should not be included in the data gathered by a particular crawler, or that a particular crawler is using up too much bandwidth, to request that crawler not to visit those pages.

Uses RF Distribution - TVs that do not require special cables or wiring but use simple RF distribution systems currently found in most locations with cable access.

UTRAN - UMTS Terrestrial Radio Access Network, is a collective term for the Node-B's and Radio Network Controllers which make up the UMTS radio access network. This communications network, commonly referred to as 3G (for 3rd Generation Wireless Mobile Communication Technology), can carry many traffic types from real-time Circuit Switched to IP based Packet Switched. The UTRAN allows connectivity between the UE (user equipment) and the core network. UMTS is using code division multiple access (CDMA). See also GERAN. The UTRAN contains the base stations, which are called Node Bs, and Radio Network Controllers (RNC). The RNC provides control functionalities for one or more Node Bs. A Node B and an RNC can be the same device, although typical implementations have a separate RNC located in a central office serving multiple Node B's. Despite the fact that they do not have to be physically separated, there is a logical interface between them known as the Iub. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS). There can be more than one RNS present in an UTRAN.  There are four interfaces connecting the UTRAN internally or externally to other functional entities: lu, Uu, lub and lur. The lu interface is an external interface that connects the RNC to the Core Network (CN). The Uu is also external, connecting the Node B with the User Equipment (UE). The lub is an internal interface connecting the RNC with the Node B. And at last there is the lur interface which is an internal interface most of the time, but can, exceptionally be an external interface too for some network architectures. The lur connects two RNCs with each other.

UV - Ultraviolet radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. It can be subdivided into near UV (380–200 nm wavelength) and extreme or vacuum UV (200–10 nm). When considering the effects of UV radiation on human health and the environment, the range of UV wavelengths is often subdivided into UVA (380–315 nm), also called Long Wave or "blacklight"; UVB (315–280 nm), also called Medium Wave; and UVC (280-10 nm), also called Short Wave or "germicidal".



8-VSB - (8-level vestigial sideband) is a standard radio frequency (RF) modulation format chosen by the Advanced Television Systems Committee (ATSC) for the transmission of digital television (DTV) to consumers in the United States and other adopting countries. In the US, the standard is specified by the Federal Communications Commission (FCC) for all digital television broadcasting. Countries in Europe and elsewhere have adopted the COFDM format.

V.80 - Application interface defined in the H.324 ITU videoconferencing standards.  It provides a standard method for H.324 applications to communicates over modems.  Also see H.324

ViDe - Video Development Group. Currently consists of the Georgia Institute of Technology, North Carolina State University, the University of North Carolina, Chapel Hill, and the University of Tennessee, Knoxville, in partnership with NYSERNet (New York State Education, Research Network).

Video on demand - Being able to view any of a number of videos when you want to. Used on the internet and at hotels, cable systems, etc.

Video server - A computer server that has been designed to store large amounts of video and stream it to users as required. Usually a video server has large amounts of high speed disks and a large amount of network bandwidth to allow for many users to simultaneously view videos.

Video Stream - A bit sequence of compressed digital video.  Another term for a video sequence.

Videoconferencing - also known as a video teleconference is a set of interactive telecommunication technologies which allow two or more locations to interact via two-way video and audio transmissions simultaneously. It has also been called visual collaboration and is a type of groupware.   Simple analog videoconferences could be established as early as the invention of the television. Such videoconferencing systems consisted of two closed-circuit television systems connected via cable. During the first manned space flights, NASA used two radiofrequency (UHF or VHF) links, one in each direction. TV channels routinely use this kind of videoconferencing when reporting from distant locations, for instance. Then mobile links to satellites using special trucks became rather common. This technique was very expensive, though, and could not be used for more mundane applications, such as telemedicine, distance education, business meetings, and so on, particularly in long-distance applications. Attempts at using normal telephony networks to transmit slow-scan video, such as the first systems developed by AT&T, failed mostly due to the poor picture quality and the lack of efficient video compression techniques. It was only in the 1980s that digital telephony transmission networks became possible, such as ISDN, assuring a minimum bandwidth (usually 128 kilobits/sec) for compressed video and audio transmission. The first dedicated systems, such as those manufactured by pioneering VTC firms, like PictureTel, started to appear in the market as ISDN networks were expanding throughout the world. Video teleconference systems throughout the 1990's rapidly evolved from highly expensive proprietary equipment, software and network requirements to standards based technology that is readily available to the general public at a reasonable cost. Finally, in the 1990s, IP (Internet Protocol) based videoconferencing became possible, and more efficient video compression technologies were developed, permitting desktop, or personal computer (PC)-based videoconferencing. VTC arrived to the masses and free services and software, such as NetMeeting, MSN Messenger, Yahoo Messenger, and others brought cheap, albeit low-quality, VTC.

The core technology used in a video teleconference (VTC) system is digital compression of audio and video streams in real time. The hardware or software that performs compression is called a codec (coder/decoder). Compression rates of up to 1:500 can be achieved. The resulting digital stream of 1's and 0's is subdivided into labeled packets, which are then transmitted through a digital network of some kind (usually ISDN or IP). The use of audio modems in the transmission line allow for the use of POTS, or the plain telephony network in some low-speed applications, such as video telephony, because they convert the digital pulses to/from analog waves in the audio spectrum range. The other components required for a VTC system include:
bulletvideo input: video camera or webcam
bulletvideo output: computer monitor or television
bulletaudio input: microphones
bulletaudio output: usually loudspeakers associated with the display device or telephone
bulletdata transfer: analog or digital telephone network, LAN or Internet
There are basically two kinds of VTC systems:
  1. Dedicated systems have all required components packaged into a single piece of equipment, usually a console with a high quality remote controlled video camera. These cameras can be controlled at a distance to pan left and right, tilt up and down, and zoom. They became known as PTZ cameras. The console contains all electrical interfaces, the control computer, and the software or hardware-based codec. Omnidirectional microphones are connected to the console, as well as a TV monitor with loudspeakers and/or a video projector. There are several types of dedicated VTC devices:
    1. Large group VTC are non-portable, large, more expensive devices used for large rooms and auditoriums.
    2. Small group VTC are non-portable or portable, smaller, less expensive devices used for small meeting rooms.
    3. Individual VTC are usually portable devices, meant for single users, have fixed cameras, microphones and loudspeakers integrated into the console.
  2. Desktop systems are add-ons (hardware boards, usually) to normal PC's, transforming them into VTC devices. A range of different cameras and microphones can be used with the board, which contains the necessary codec and transmission interfaces. Most of the desktops systems work with the H.323 standard. Video conferences carried out via dispersed PCs are also known as e-meetings.
A fundamental feature of professional VTC systems is Acoustic Echo Cancellation (AEC). AEC is an algorithm which is able to detect when sounds or utterances reenter the audio input of the VTC codec, which came from the audio output of the same system, after some time delay. If unchecked, this can lead to several problems including 1) the remote party hearing their own voice coming back at them (usually significantly delayed) 2) strong reverberation, rendering the voice channel useless as it becomes hard to understand and 3) howling created by feedback. Echo cancellation is a processor-intensive task that usually works over a narrow range of sound delays. Simultaneous videoconferencing among three or more remote points is possible by means of a Multipoint Control Unit (MCU). This is a bridge that interconnects calls from several sources (in a similar way to the audio conference call). All parties call the MCU unit, or the MCU unit can also call the parties which are going to participate, in sequence. There are MCU bridges for IP and ISDN-based videoconferencing. There are MCUs which are pure software, and others which are a combination of hardware and software. An MCU is characterized according to the number of simultaneous calls it can handle. MCUs can be stand-alone hardware devices, or they can be embedded into dedicated VTC units.

Standards: The International Telecommunications Union (ITU) (formerly: Consultative Committee on International Telegraphy and Telephony (CCITT)) has three umbrellas of standards for VTC:

  1. ITU H.320 is known as the standard for public switched telephone networks (PSTN) or VTC over integrated services digital networks (ISDN) basic rate interface (BRI) or primary rate interface (PRI). H.320 is also used on dedicated networks such as T1 and satellite-based networks;

  2. ITU H.323 is known as the standard for video over Internet Protocol (IP). This same standard also applies to voice over IP VoIP);
  3. ITU H.324 is the standard for transmission over POTS, or audio telephony networks.
In recent years, IP based videoconferencing has emerged as a common communications interface and standard provided by VTC manufacturers in their traditional ISDN-based systems. Business, government and military organizations still predominantly use H.320 and ISDN VTC. Though, due to the price point and proliferation of the Internet, and broadband in particular, there has been a strong spurt of growth and use of H.323, IP VTC. H.323 has the advantage that it is accessible to anyone with a high speed Internet connection, such as  DSL.  In addition, an attractive factor for IP VTC is that it is easier to set-up for use with a live VTC call along with data collaboration [web conferencing (ITU T.120 standard)]. These combined technologies enable users to have a much richer multimedia environment for live meetings, collaboration and presentations. Videoconferencing is a very useful technology for telemedicine and telenursing applications, such as diagnosis, consulting, transmission of medical images, etc., in real time. Using VTC, patients may contact nurses and physicians in medical emergency or routine situations, physicians and other paramedical professionals can discuss cases across large distances. Rural areas can use this technology for diagnostic purposes, thus saving lives and making more efficient use of health care dollars.  Special peripherals such as microscopes fitted with digital cameras, videoendoscopes, medical ultrasound imaging devices, Otoscope, etc., can be used in conjunction with VTC equipment to transmit data about a patient.

VLAN - A virtual LAN, commonly known as a vLAN, is a logically-independent network. Several VLANs can co-exist on a single physical switch. A VLAN consists of a network of computers that behave as if connected to the same wire - even though they may actually physically connect to different segments of a LAN. Network administrators configure VLANs through software rather than hardware, which makes them extremely flexible. One of the biggest advantages of VLANs emerges when physically moving a computer to another location: it can stay on the same VLAN without the need for any hardware reconfiguration.  The IEEE 802.1Q tagging protocol dominates the VLAN world. Prior to the introduction of 802.1Q several proprietary protocols existed, such as Cisco's ISL (Inter-Switch Link, a variant of IEEE 802.10) and 3Com VLT (Virtual LAN Trunk). Some users now deprecate ISL in favor of 802.1Q. Virtual LANs operate at layer 2 (the data link layer) of the OSI model. However, administrators often configure a VLAN to map directly to an IP network, or subnet, which gives the appearance of involving layer 3 (the network layer).  In the context of VLANs, the term "trunk" denotes a network link carrying multiple VLANs which are identified by labels (or "tags") inserted into their packets. Such trunks must run between "tagged ports" of VLAN-aware devices, so are often switch-to-switch or switch-to-router links rather than links to hosts. (Confusingly, the term 'trunk' also gets used for what Cisco call "channels" : Link Aggregation or Port Trunking). A router (Layer 3 switch) serves as the backbone for network traffic going across different VLANs. On Cisco devices, VTP (VLAN Trunking Protocol) allows for VLAN domains, which can aid in administrative tasks. VTP also allows "pruning", which involves directing specific VLAN traffic only to switches which have ports on the target VLAN.

VLR - The Visitor Location Register is a database, part of the GSM system, which stores information about all the mobiles that are currently under the jurisdiction of the MSC to which VLR is attached.  Each Base Station in the network is served by exactly one VLR, hence a subscriber cannot be present in more than one VLR at a time. The data stored in the VLR has either been received from the HLR, or collected from the Mobile Station (MS). Whenever MSC detects a new MS in its network, in addition to creating a new record in VLR, it also updates the HLR of the mobile subscriber apprising it about the new location of MS.  In practice, for performance reasons, most vendors integrate the VLR directly to the V-MSC and, where this is not done, the VLR is very tightly linked with the MSC via a proprietary interface. Of all the information it stores about MS, the most important is LAI (Location Area Identity). LAI identifies under which BSC (Base Station Controller) is the MS currently present. This information is very vital in call set up process.  Data stored includes:

bulletIMSI (the subscriber's identity number)
bulletauthentication data
bulletMSISDN (the subscriber's phone number)
bulletGSM services that the subscriber is allowed to access
bulletAccess Point (GPRS) subscribed
bulletthe HLR address of the subscriber

Voice activated switching - Automatically switching the video feed to whomever is speaking in a multipoint video conference. Usually a function of the MCU (multipoint conferencing unit)

Voice over PSN (Packet Switching Network) -  VoIP and VoFR are technologies that use Access Devices (such as VFRADs/Routers and so forth) that employ sophisticated schemes to overcome the limitations. Prioritization, fragmentation, silence suppression, voice compression, packet loss concealment (PLC) are example of such schemes.

VoIP - Voice over Internet Protocol also known as VoP (Voice over Packets), allows the voice to travel simultaneously over a single packet network line with both fax and modem data.

VoFR - VoFR (Voice over Frame Relay) enables a router to carry voice traffic, such as telephone calls and faxes, over a frame relay network.

VoATM - Voice over ATM enables an ATM switch to carry voice traffic over an ATM network.

VPN - Virtual Private Network.  is a private communications network usually used within a company, or by several different companies or organizations, communicating over a public network. VPN message traffic is carried on public networking infrastructure (e.g. the Internet) using standard (often insecure) protocols, or over a service providers network providing VPN service guarded by well defined Service Layer Agreement (SLA) between the VPN customer and the VPN Service Provider.  There are three main types of VPN: Intranet VPN over a common network infrastructure, Remote Access VPN mainly for users with laptop connecting intermittently from vary diverse locations , and Extranet VPN using the Internet as the backbone networkSecure VPNs use cryptographic tunneling protocols to provide the necessary confidentiality (preventing snooping), sender authentication (preventing identity spoofing), and message integrity (preventing message alteration) to achieve the privacy intended. When properly chosen, implemented, and used, such techniques can provide secure communications over unsecured networks.  Because such choice, implementation, and use are not trivial, there are many insecure VPN schemes on the market.  Secure VPN technologies may also be used to enhance security as a 'security overlay' within dedicated networking infrastructures.

Secure VPN protocols include the following: 1-) IPsec (IP security), an obligatory part of IPv6.  1a-) L2TP and L2TPv3: inside of IPsec , 2-) SSL used either for tunneling the entire network stack, such as in OpenVPN, or for securing what is essentially a web proxy. Although the latter is often called a "SSL VPN" by VPN vendors, it is not really a fully-fledged VPN.  3-) PPTP (point-to-point tunneling protocol), developed by Microsoft.

Some large ISPs now offer "managed" VPN service for business customers who want the security and convenience of a VPN but prefer not to undertake administering a VPN server themselves. In addition to providing remote workers with secure access to their employer's internal network, sometimes other security and management services are included as part of the package, such as keeping anti-virus and anti-spyware programs updated on each client's computer.

Trusted VPNs do not use cryptographic tunneling, and instead rely on the security of a single provider's network to protect the traffic. Multi-protocol label switching (MPLS) is commonly used to build trusted VPNs. Other protocols for trusted VPNs include: 1-) L2F (Layer 2 Forwarding), developed by Cisco. 2-) L2TP (Layer 2 Tunneling Protocol), including work by both Microsoft and Cisco. 3-) L2TPv3 (Layer 2 Tunneling Protocol version 3).

VToA - Voice Telephony over ATM is based on ATM Forum specification atm-vtoa-0078, which was developed for carrying CBR (Continuous Bit Rate) services over ATM.

V-Chip Compliant - Allows viewer to set level of access to certain channels and/or programs. The access level is dictated by the TV Parental Guidelines rating assigned to all television programs.

VGA (Video Graphics Array) - Introduced by IBM in 1987, VGA is an Analog signal with TTL level separate horizontal and vertical sync. The video outputs to a 15-pin, HD connector and has a horizontal scan frequency of 31.5 kHz and vertical frequency of 70 Hz (Mode 1, 2) and 60 Hz (Mode 3). The signal is non-interlaced in modes 1, 2, 3 and interlaced when using the 8514/A card (35.5 kHz, 86 Hz) in mode 4. It has a Pixel by Line resolution of 640 x 480 with a color palette of 16/256,000.

Volume Limiter - Allows both the minimum and maximum volume range to set to a pre-determined level, preventing volume from being adjusted too high or too low when in use.

Volume Management - Acting as a volume limiter, this feature offers the ability to limit the maximum and in some televisions, the minimum volume coming from the set. The volume can also be set to a volume lock mode so that the volume cannot be turned up or down. Finally the volume can also be set to an on mode where the volume will always come up to the right level.



WAN - Wide Are Network.  Computer and voice network bigger than a city or metropolitan area.

WAP - Wireless Application Protocol, a secure specification that allows users to access information instantly via handheld wireless devices such as mobile phones, pagers, two-way radios, smartphones and communicators. WAP is a set of standards that enables a wireless device to browse content from specially-coded Web pages. The WAP 2.0 specification integrates capabilities of the rival i-mode standard.

wavelength - is the distance between repeating units of a wave pattern. It is commonly designated by the Greek letter lambda (λ).  In a sine wave, the wavelength is the distance between peaks

W-CDMA - Wideband CDMA (WCDMA) is a version of CDMA that uses 10 MHz of wireless spectrum: a 5-MHz uplink from the mobile terminal and a 5-MHz downlink to the mobile terminal. The version of WCDMA used by NTT DoCoMo in Japan is called FOMA or J-WCDMA; the European version is referred to as UMTS or E-WCDMA.

WBS - In project management, a work breakdown structure (WBS) is an exhaustive, hierarchical (from general to specific) tree structure of deliverables and tasks that need to be performed to complete a project.

Web Portal - Web portals are sites on the World Wide Web that typically provide personalized capabilities to their visitors. They are designed to use distributed applications, different numbers and types of middleware and hardware to provide services from a number of different sources. In addition, business portals are designed to share collaboration in workplaces. A further business-driven requirement of portals is that the content be able to work on multiple platforms such as personal computers, personal digital assistants (PDAs), and cell phones.  In the late 1990s, the Web portal was a hot commodity. After the proliferation of Web browsers in the mid-1990s, many companies tried to build or acquire a portal, to have a piece of the Internet market. The Web portal gained special attention because it was, for many users, the starting point of their Web browser. Netscape Netcenter became a part of America Online, the Walt Disney Company launched Go.com, and Excite became a part of AT&T during the late 1990s. Lycos was said to be a good target for other media companies such as CBS.Many of the portals started initially as either web directories (notably Yahoo!) and/or search engines (Excite, Lycos, AltaVista, infoseek, and Hotbot among the old ones). The expansion of service provision occurred as a strategy to secure the user-base and lengthen the time a user stays on the portal. Services which require user registration such as free email, customization features, and chatrooms were considered to enhance repeat use of the portal. Game, chat, email, news, and other services also tend to make users stay longer, thereby increasing the advertisement revenue.  The portal craze, with "old media" companies racing to outbid each other for Internet properties, died down with the dot-com burst in 2000 and 2001. Disney pulled the plug on Go.com, Excite went bankrupt and its remains were sold to iWon.com. Some notable portal sites --- for instance, Yahoo!, remain successful to this day. To modern dot-com businesses, the portal craze serves as a cautionary tale about the risks of rushing into a market crowded with highly-capitalized but largely undifferentiated me-too companies.

Web service - According to the W3C a Web service (or Web Service) is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface that is described in a machine process-able format such as WSDL. Other systems interact with the Web service in a manner prescribed by its interface using messages, which may be enclosed in a SOAP envelope, or follow a REST approach. These messages are typically conveyed using HTTP, and normally comprise XML in conjunction with other Web-related standards. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (for example, between Java and Python, or Microsoft Windows and Linux applications) is due to the use of open standards. OASIS and the W3C are the primary committees responsible for the architecture and standardization of web services. To improve interoperability between web service implementations, the WS-I organization has been developing a series of profiles to further define the standards involved.  Web services standards features such as transactions are currently nonexistent or still in their infancy compared to more mature distributed computing open standards such as CORBA. This is likely to be a temporary disadvantage as most vendors have committed to the OASIS standards to implement the Quality of Service aspects of their products. Web services may suffer from poor performance compared to other distributed computing approaches such as RMI, CORBA, or DCOM.  The standards used:

bulletWeb Services Protocol Stack: The Standards and protocols used to consume a web service, considered as a protocol stack.
bulletXML: All data to be exchanged is formatted with XML tags. The encoded message may conform to a messaging standard such as SOAP or the older XML-RPC. The XML-RPC scheme calls functions remotely, whilst SOAP favors a more modern (object-oriented) approach based on the Command pattern.
bulletCommon protocols: data can be transported between applications using any number of common protocols, such as HTTP, FTP, SMTP and XMPP.
bulletWSDL: The public interface to the web service is described by Web Services Description Language, or WSDL. This is an XML-based service description on how to communicate using the web service.
bulletUDDI: The web service information is published using this protocol. It should enable applications to look up web services information in order to determine whether to use them.
bulletebXML: A modular electronic business framework is enabled using this set of specifications. The vision of ebXML is to enable a global electronic marketplace where enterprises of any size and in any geographical location can meet and conduct business with each other through the exchange of XML-based messages.
bullet WS-Security: The Web Services Security protocol has been accepted as an OASIS standard. The standard allows authentication of actors and confidentiality of the messages sent.
bullet WS-ReliableExchange: A SOAP-based specification that fulfills reliable messaging requirements critical to some applications of Web Services. Accepted as an OASIS standard.
bullet WS-Management: This specification describes a SOAP-based protocol for systems management of personal computers, servers, devices, and other manageable hardware and Web services and other applications.

WDM - In telecommunications Wavelength Division Multiplexing is a technology which multiplexes several optical carrier signals on a single optical fiber by using different wavelengths (colors) of laser light to carry different signals.

Wideband - a communications medium or signal that spans a large (continuous) range of frequencies, or is wide compared to something else.

Wideband Delphi - The Wideband Delphi estimation method is a consensus-based estimation technique for estimating effort. It was developed in the 1940s at the Rand Corporation as a forecasting tool. It has since been adapted across many industries to estimate many kinds of tasks, ranging from statistical data collection results to sales and marketing forecasts. It has proven to be a very effective estimation tool, and it lends itself well to software projects.

Windows®-based Network Control - Allows Windows®-based control of a television network using existing RF (cable) distribution system wiring with Windows 95/98/NT.

WiBro - is a Broadband Wireless internet technology being developed by the Korean telecom industry. In February 2002, the Korean Government allocated 100MHz of electromagnetic spectrum in the 2.3GHz band, and in late 2004 WiBro Phase 1 was standardized by the TTA (Telecommunications Technology Association) of Korea.  WiBro base stations will offer an aggregate data throughput of 30 to 50 Mbps and cover a radius of 1-5 km.  SK Telecom and Hanaro Telecom have announced a partnership to roll out WiBro nationwide in Korea, excluding Seoul and six provincial cities, where independent networks will be rolled out.  In November 2004, Intel and LG Electronics executives agreed to ensure compatibility between WiBro and WiMAX technology.  In September 2005, Samsung Electronics signed a deal with Sprint Nextel Corporation to provide equipment for a WiBro trial.

Wi-Fi - stands for “Wireless Fidelity” and is a logo provided by the Wireless Ethernet Compatibility Association (WECA) for the 802.11b wireless Ethernet standard. Compatible PC cards and base stations can use the Wi-Fi logo. It is a mark of compatibility.

WiMAX - WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum [1], formed in April 2001 to promote conformance and interoperability of the standard IEEE 802.16. The Forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL."  The WiMAX Forum is "the exclusive organization dedicated to certifying the interoperability of BWA products, the WiMAX Forum defines and conducts conformance and interoperability testing to ensure that different vendor systems work seamlessly with one another."  Those that pass conformance and interoperability testing achieve the “WiMAX Forum Certified” designation and display this mark on their products and marketing materials. Vendors claiming their equipment is “WiMAX-ready,” "WiMAX-compliant,” "pre-WiMAX," are not WiMAX Forum Certified, according to the Forum. [2]The IEEE 802.16 media access controller (MAC) is significantly different from that of IEEE 802.11 Wi-Fi MAC. In Wi-Fi, the MAC uses contention access—all subscriber stations wishing to pass data through an access point are competing for the AP's attention on a random basis. This can cause distant nodes from the AP to be repeatedly interrupted by less sensitive, closer nodes, greatly reducing their throughput. And this makes services, such as VoIP or IPTV which depend on a determined level of quality of service (QoS) difficult to maintain for large numbers of users.  By contrast, the 802.16 MAC is a scheduling MAC where the subscriber station only has to compete once (for initial entry into the network). After that it is allocated a time slot by the base station. The time slot can enlarge and constrict, but it remains assigned to the subscriber station meaning that other subscribers are not supposed to use it but take their turn. This scheduling algorithm is stable under overload and over-subscription (unlike 802.11). It is also much more bandwidth efficient. The scheduling algorithm also allows the base station to control Quality of Service by balancing the assignments among the needs of the subscriber stations.  A recent addition to the WiMAX standard is underway which will add full mesh networking capability by enabling WiMAX nodes to simultaneously operate in "subscriber station" and "base station" mode. This will blur that initial distinction and allow for widespread adoption of WiMAX based mesh networks and promises widespread WiMAX adoption. WiMAX/802.16's use of OFDMA and scheduled MAC allows wireless mesh networks to be much more robust and reliable. These differences between and evolution of Wi-Fi and WiMAX mesh networks could serve as a separate topic. The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004, added support for the 2 to 11 GHz range, of which most parts are already unlicensed internationally and only very few still require domestic licenses. Most business interest will probably be in the 802.16-2004 standard, as opposed to licensed frequencies. The WiMAX specification improves upon many of the limitations of the Wi-Fi standard by providing increased bandwidth and stronger encryption. It also aims to provide connectivity between network endpoints without direct line of sight in some circumstances. The details of performance under non-line of sight (NLOS) circumstances are unclear as they have yet to be demonstrated. It is commonly considered that spectrum under 5-6 GHz is needed to provide reasonable NLOS performance and cost effectiveness for PtM (point to multi-point) deployments. WiMAX makes clever use of multi-path signals but does not defy the laws of physics.  Alcatel is demonstrating its IMS (IP Multimedia Subsystem) over WiMAX services.

Wireless Operator -Wireless operator” is a general term that refers to either a wireless network operator or a wireless service operator. The wireless network operator, also called a “carrier,” maintains the radio towers and infrastructure for a cellular system. Wireless service operators sell wireless service to subscribers and contract with wireless network operators to provide their service. Outside of Europe, the wireless network operator and wireless service operator functions are combined within one company that is referred to as the “carrier” or wireless operator.

WLAN - A Wireless LAN is a wireless local area network that uses radio waves as its carrier: the last link with the users is wireless, to give a network connection to all users in the surrounding area. Areas may range from a single room to an entire campus. The backbone network usually uses cables, with one or more wireless access points connecting the wireless users to the wired network. WLAN is based on various versions of IEEE 802.11 (Wi-Fi).  802.11b (typically 30ft.), 54 Mbit/s 802.11a (5 GHz) and 802.11g (2.4 GHz).  Security is a major concern. The fact that someone can sit in the car park (or building next door), pick-up and store all your wireless traffic, and crack the most common implementation of Wireless encryption (WEP) in less than a week (and then read all the stored traffic) has to be a concern to any business operation (see Wardriving). Changing the wireless LAN encryption key on a daily or weekly basis, and then 'rolling it out' (by some means other than 'plain text' emails) is an extra overhead that many Companies never manage to achieve. IPSec is often used by larger businesses that have the infrastructure to support it. Wi-Fi Protected Access (WPA) is now available in most access points and provides adequate security for most purposes.

WMIS - Warehouse Management Information System.

WSDL - The Web Services Description Language (WSDL) is an XML format published for describing Web services. Version V 1.1 has not been endorsed by the World Wide Web Consortium (W3C), however it has released a draft for version 2.0 on May 11, 2005, that will be a W3C recommendation, and thus endorsed by the W3C.  It is commonly abbreviated as WSDL in technical literature and is usually pronounced wiz-dell.  WSDL describes the public interface to the web service. This is an XML-based service description on how to communicate using the web service; namely, the protocol bindings and message formats required to interact with the web services listed in its directory. The supported operations and messages are described abstractly, and then bound to a concrete network protocol and message format.  WSDL is often used in combination with SOAP and XML Schema to provide web services over the internet. A client program connecting to a web service can read the WSDL to determine what functions are available on the server. Any special datatypes used are embedded in the WSDL file in the form of XML Schema. The client can then use SOAP to actually call one of the functions listed in the WSDL.  XLang is a extension of the WSDL such that "an XLANG service description is a WSDL service description with an extension element that describes the behavior of the service as a part of a business process"



XACML - stands for eXtensible Access Control Markup Language. It is a declarative access control policy language implemented in XML.  Version 2.0 was ratified by OASIS standards organization on 1 February 2005.

xDSL - The letter x means generic - term for Digital Subscriber Line equipments and services, including ADSL, HDSL, IDSL, SDSL, and VDSL.  xDSL technology provide extremely high bandwidth over the twisted-pair that runs from your phone company's central office to your office or home.

XGA - Extended Graphics Array card. IBM's graphics standard that includes VGA and extended resolutions up to 1024 x 768, interlaced; 35 kHz. This card has a 15-pin HD connector.

XML - The Extensible Markup Language is a W3C-recommended general-purpose markup language for creating special-purpose markup languages, capable of describing many different kinds of data. It is a simplified subset of Standard Generalized Markup Language (SGML). Its primary purpose is to facilitate the sharing of data across different systems, particularly systems connected via the Internet. Languages based on XML (for example, Geography Markup Language (GML), RDF/XML, RSS, MathML, Physical Markup Language (PML), XHTML, SVG, MusicXML and cXML) are defined in a formal way, allowing programs to modify and validate documents in these languages without prior knowledge of their form.



Y/C - Two channel video channel.  One used for color (chrominance) and the other for black and white (luminance).  This designation is used for video signals that keeps separate the luminance and the chrominance information; thus, preventing some of the normal NTSC artifacts like E.G., cross-color, and cross-luminance.

YUV - A color encoding scheme for natural pictures in which luminance and chrominance are separate.  Three image components  that provide alternative representation of red, green, and blue. (See RGB). The human eye is less sensitive to color variation than to intensity variation. YUV allows the encoding of luminance (Y) information at full bandwidth and chrominance (UV) information at half bandwidth.

YUV9 - The color encoding scheme used in Indeo Video Technology.  The YUV9 format stores information in 4x4 pixel blocks.  16 bytes of luminance are stored for every 1 byte of chrominance.  For example, a 640x480 image will have 307,200 bytes of luminance and 19,200 bytes of chrominance.



ZV - Zoomed Video - Technology that allows certain streams of digital information to write directly to a laptop's screen; thus, bypassing the CPU and its bus (ISA, PCI, EISA, etc.).  Zoomed Video can show full 30 frames per second movies to a laptop screen.  ZV technology is to bring full laptop screen videoconferencing to laptop.



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