Teledatacom Dictionary A-M
Provides special services such as Custom Local Area Signaling Services (CLASS) for Caller ID, automatic callback, 911, etc. The adjunct performs similar functions to an SCP, but at a local level.
ADSL (Asymmetrical Digital Subscriber Line)
ADSL is a technology for transmitting digital information at a high bandwidth on existing phone lines to homes and businesses. Unlike regular dialup phone service, ADSL provides continously-available, "always on" connection. ADSL is asymmetric in that it uses most of the channel to transmit downstream to the user and only a small part to receive information from the user. ADSL simultaneously accommodates analog (voice) information on the same line. ADSL is generally offered at downstream data rates from 512 Kbps to about 6 G.lite, has been approved as a standard by the ITU-TS.
A series of specifications for a Mezzanine card to be used in AdvancedTCA or other systems to add modular functionality. AMC.0 defines the base mechanicals and functionality with additional specs for optional fabric extensions.
Advanced Telecom Computing Architecture (AdvancedTCA®) is the largest specification effort in PICMG's history, with more than 100 companies participating. AdvancedTCA, the PICMG 3.X family, is a new series of PICMG specifications, targeted to requirements for the next generation of carrier grade communications equipment. This series of specifications incorporates the latest trends in high speed interconnect technologies, next generation processors and improved reliability, manageability and serviceability.
In telecommunications, an analog signal is one in which a base carrier's alternating current frequency is modified in some way, such as by amplifying the strength of the signal or varying the frequency, in order to add information to the signal.
Broadcast and telephone transmission has conventionally used analog technology. An analog signal can be represented as a series of sine waves. The term originated because the modulation of the carrier wave is analogous to the fluctuations of the human voice or other sound that is being transmitted.
In the Open Systems Interconnection (OSI) communications model, the Application layer provides services for application programs that ensure that communication is possible. The Application layer is NOT the application itself that is doing the communication. It is a service layer that provides these services:
Makes sure that the other party is identified and can be reached
If appropriate, authenticates either the message sender or receiver or both
Makes sure that necessary communication resources exist (for example, is there a modem in the sender's computer?)
Ensures agreement at both ends about error recovery procedures, data integrity, and privacy
Determines protocol and data syntax rules at the application level
A server in a distributed network that provides other systems or end users execution resources for a defined set of applications.
ATM (Asynchronous Transfer Mode)
ATM is a dedicated-connection switching technology that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path.
Because ATM is designed to be easily implemented by hardware (rather than software), faster processing and switch speeds are possible. The prespecified bit rates are either 155.520 Mbps or 622.080 Mbps. Speeds on ATM networks can reach 10 Gbps. Along with Synchronous Optical Network (SONET) and several other technologies, ATM is a key component of broadband ISDN (BISDN).
BISDN is both a concept and a set of services and developing standards for integrating digital transmission services in a broadband network of fiber optic and radio media. BISDN will encompass frame relay service for high-speed data that can be sent in large bursts, the Fiber Distributed-Data Interface (FDDI), and the Synchronous Optical Network (SONET). BISDN will support transmission from 2 Mbps up to much higher, but as yet unspecified, rates.
Bandwidth has a general meaning of how much information can be carried in a given time period (usually a second) over a wired or wireless communications link. For example, a link with a broad bandwidth - that is, a broadband link - is one that may be able to carry enough information to sustain the succession of images in a video presentation.
More technically, bandwidth is the width of the range of frequencies that an electronic signal occupies on a given transmission medium. Any digital or analog signal has a bandwidth.
In digital systems, bandwidth is expressed as bits (of data) per second (bps). Thus, a modem that works at 57,600 bps has twice the bandwidth of a modem that works at 28,800 bps. In analog systems, bandwidth is expressed in terms of the difference between the highest-frequency signal component and the lowest-frequency signal component. Frequency is measured in the number of cycles of change per second, or hertz. A typical voice signal has a bandwidth of approximately three kilohertz (3 kHz); an analog television (TV) broadcast video signal has a bandwidth of six megahertz (6 MHz) -- some 2,000 times as wide as the voice signal.
A bit (short for binary digit) is the smallest unit of data in a computer. A bit has a single binary value, either 0 or 1. Although computers usually provide instructions that can test and manipulate bits, they generally are designed to store data and execute instructions in bit multiples called bytes. In most computer systems, there are eight bits in a byte. The value of a bit is usually stored as either above or below a designated level of electrical charge in a single capacitor within a memory device.
The BSC works with Base Transceiver Stations to act as a link between wireless devices such as cell phones and the wireline telephone network.
BTS (Base Transceiver Station)
The Base Transceiver Station is the transmit and receive link for a mobile communication system. It's the device that actually communicates with the cell phone or PCS phone. The BTS connects to a BSC over a T1/E1 line.
In most computer systems, a byte is a unit of data that is eight binary digits long. A byte is the unit most computers use to represent a character such as a letter, number, or typographic symbol (for example, "g", "5", or "?"). A byte can also hold a string of bits that need to be used in some larger unit for application purposes (for example, the stream of bits that constitute a visual image for a program that displays images or the string of bits that constitutes the machine code of a computer program).
A control center of a Cable TV system, where incoming signals are amplified, converted, processed, and combined into a common cable for transmission to customers. Cable headends also provide high-speed internet access and data service.
A cable modem is a device that enables you to hook up your PC to a local cable TV line and receive data at about 1.5 Mbps. This data rate far exceeds that of the prevalent 28.8 and 56 Kbps telephone modems and the up to 128 Kbps of Integrated Services Digital Network (ISDN) and is about the data rate available to subscribers of Digital Subscriber Line (DSL) telephone service. A cable modem can be added to or integrated with a set-top box that provides your TV set with channels for Internet access. In most cases, cable modems are furnished as part of the cable access service and are not purchased directly and installed by the subscriber.
A cable modem has two connections: one to the cable wall outlet and the other to a PC or to a set-top box for a TV set. Although a cable modem does modulation between analog and digital signals, it is a much more complex device than a telephone modem. It can be an external device or it can be integrated within a computer or set-top box. Typically, the cable modem attaches to a standard 10BASE-T Ethernet card in the computer.
All of the cable modems attached to a cable TV company coaxial cable line communicate with a Cable Modem Termination System (CMTS) at the local cable TV company office. All cable modems can receive from and send signals only to the CMTS, but not to other cable modems on the line. Some services have the upstream signals returned by telephone rather than cable, in which case the cable modem is known as a telco-return cable modem.
The actual bandwidth for Internet service over a cable TV line is up to 27 Mbps on the download path to the subscriber with about 2.5 Mbps of bandwidth for interactive responses in the other direction. However, since the local provider may not be connected to the Internet on a line faster than a T-carrier system at 1.5 Mpbs, a more likely data rate will be close to 1.5 Mpbs.
CDMA (Code-Division Multiple Access)
CDMA refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.
CDMA employs analog-to-digital conversion (ADC) in combination with spread spectrum technology. Audio input is first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes; this enhances privacy and makes cloning difficult.
In telephone communication in the United States, a central office (CO) is an office in a locality to which subscriber home and business lines are connected on what is called a local loop. The central office has switching equipment that can switch calls locally or to long-distance carrier phone offices.
CGF (Charging Gateway Function)
A billing system in the wireless networks.
Circuit-switched is a type of network in which a physical path is obtained for and dedicated to a single connection between two end-points in the network for the duration of the connection. Ordinary voice phone service is circuit-switched. The telephone company reserves a specific physical path to the number you are calling for the duration of your call. During that time, no one else can use the physical lines involved.
CLEC (Competitive Local Exchange Carrier)
In the United States, a CLEC is a company that competes with the already established local telephone business by providing its own network and switching. The term distinguishes new or potential competitors from established local exchange carriers (LEC) and arises from the Telecommunications Act of 1996, which was intended to promote competition among both long-distance and local phone service providers. North American Telecom and Winstar Communications are examples of CLECs (which generally are listed as simply "local exchange carriers.")
Coaxial cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses. Coaxial cable is sometimes used by telephone companies from their central office to the telephone poles near users. It is also widely installed for use in business and corporation Ethernet and other types of local area network.
Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can carry information for a great distance.
Coaxial cable was invented in 1929 and first used commercially in 1941. AT&T established its first cross-continental coaxial transmission system in 1940. Depending on the carrier technology used and other factors, twisted pair copper wire and optical fiber are alternatives to coaxial cable.
Digital describes electronic technology that generates, stores, and processes data in terms of two states: positive and non-positive. Positive is expressed or represented by the number 1 and non-positive by the number 0. Thus, data transmitted or stored with digital technology is expressed as a string of 0's and 1's. Each of these state digits is referred to as a bit (and a string of bits that a computer can address individually as a group is a byte).
A multiplexing/de-multiplexing system that typically has a high bandwidth fiber connection to a Central Office out one side, and provides copper interfaces to many residences out the other side. DLC's are deployed where there is fiber installed to a neighborhood, but copper to the homes. DLC's are less expensive to deploy than Fiber to the Home or Fiber to the Curb because there's only one optoelectric conversion required.
DSL is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL. Assuming your home or small business is close enough to a telephone company central office that offers DSL service, you may be able to receive data at rates up to 6.1 megabits (millions of bits) per second (of a theoretical 8.448 megabits per second), enabling continuous transmission of motion video, audio, and even 3-D effects. More typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected.
DSLAM (Digital Subscriber Line Access Multiplexer)
DSLAM is a network device, usually at a telephone company central office, that receives signals from multiple customer Digital Subscriber Line (DSL) connections and puts the signals on a high-speed backbone line using multiplexing techniques. Depending on the product, DSLAM multiplexers connect DSL lines with some combination of asynchronous transfer mode (ATM), frame relay, or Internet Protocol networks. DSLAM enables a phone company to offer business or homes users the fastest phone line technology (DSL) with the fastest backbone network technology (ATM).
DWDM (Dense Wavelength Division Multiplexing)
Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical fiber. Each channel carries a time division multiplexed (TDM) signal. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical fiber. DWDM is also sometimes called wave division multiplexing (WDM).
Since each channel is demultiplexed at the end of the transmission back into the original source, different data formats being transmitted at different data rates can be transmitted together. Specifically, Internet (IP) data, Synchronous Optical Network data (SONET), and asynchronous transfer mode (ATM) data can all be travelling at the same time within the optical fiber.
DWDM promises to solve the "fiber exhaust" problem and is expected to be the central technology in the all-optical networks of the future.
E1 (or E-1) is a European digital transmission format devised by the ITU-TS and given the name by the Conference of European Postal and Telecommunication Administration (CEPT). It's the equivalent of the North American T-carrier system format. E2 through E5 are carriers in increasing multiples of the E1 format.
The E1 signal format carries data at a rate of 2.048 million bits per second and can carry 32 channels of 64 Kbps* each. E1 carries at a somewhat higher data rate than T-1 (which carries 1.544 million bits per second) because, unlike T-1, it does not do bit-robbing and all eight bits per channel are used to code the signal. E1 and T-1 can be interconnected for international use.
An Enterprise Gateway is customer premises equipment that provides conversion between the audio signals carried on telephone circuits and data packets carried over the Local Area Network. Enterprise Gateways are very similar to Media Gateways, but are scaled and configured to meet the needs of the enterprise rather than a carrier.
Ethernet is the most widely-installed local area network (LAN) technology. Specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox and then developed further by Xerox, DEC, and Intel. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet is also used in wireless LANs. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.
Fast Ethernet or 100BASE-T provides transmission speeds up to 100 megabits per second and is typically used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an even higher level of backbone support at 1000 megabits per second (1 gigabit or 1 billion bits per second). 10-Gigabit Ethernet provides up to 10 billion bits per second.
FDDI (Fiber Distributed Data Interface) is a set of ANSI and ISO standards for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol. In addition to being large geographically, an FDDI local area network can support thousands of users. FDDI is frequently used on the backbone for a wide area network (WAN).
An FDDI network contains two token rings, one for possible backup in case the primary ring fails. The primary ring offers up to 100 Mbps capacity. If the secondary ring is not needed for backup, it can also carry data, extending capacity to 200 Mbps. The single ring can extend the maximum distance; a dual ring can extend 100 km (62 miles).
FDDI is a product of American National Standards Committee X3-T9 and conforms to the Open Systems Interconnection (OSI) model of functional layering. It can be used to interconnect LANs using other protocols. FDDI-II is a version of FDDI that adds the capability to add circuit-switched service to the network so that voice signals can also be handled. Work is underway to connect FDDI networks to the developing Synchronous Optical Network (SONET).
Frame Relay is a data communications protocol designed for highly bandwidth efficient transmission across packet switched networks. It sits at layer two (Data Link Layer) in the OSI seven layer model.
Frame Relay offers high data payload per frame, congestion control, network management and fast/efficient frame forwarding. It offers both PVCs (for always-on connection between sites) and SVCs (an on-demand service).
In a Frame Relay network, data is sent in a variable length unit called a 'frame'. Although variable, a frame has a maximum length - Frame Relay supports fragmentation and reassembly of data in order to cope with larger packets sent by its users.
The physical medium for transmission is usually a T1 or E1 line (either as a single channel, across a number of channels, or across all available channels). Each connection is assigned a Data Link Connection Identifier (DLCI).
One of the key benefits of Frame Relay is that it adds a very small protocol header to each frame. This is achieved by removing the fields used for error correction in the header (the frame sequence numbers). If an error is detected in a frame, the recovery mechanism is simple: discard the data. The rationale behind this is twofold. Firstly, digital transmission lines (T1 and E1) have become incredibly reliable - frame error rates are so low that the error detection and recovery mechanism in older packet switched technology (such as X.25) is seen as an unnecessary overhead. Secondly, the higher layer protocols (such as TCP) which make use of Frame Relay have their own retransmission mechanisms to recover from lost data - why replicate it in both layers?
Another key benefit of Frame Relay is congestion control. This is done by offering subscribers a service based on the throughput they expect to use. Each DLCI is given a Committed Information Rate (CIR) - the rate at which users are guaranteed to be able to send data. A DLCI is also given a Committed Burst size (Bc) which allows users to send data at faster rates for a short period of time. In addition to this, DLCIs have an Excess Burst size (Be) which allows an application to exceed the Bc when bandwidth is available (i.e. when other connections are being under-utilised) - with the danger that excess burst data may be discarded under heavy load conditions.
Frame Relay was originally designed as a WAN protocol used to connect LAN's for data transfer between remote sites (e.g. to link a number of offices). As it provides little in the way of deterministic transmission times, it is not ideal for packetised voice.
More recently, Frame Relay has found a new application in 2.5G mobile networks, being used to transfer signalling data between the BSC and MSC.
G.Lite is the informal name for what is now a standard way to install Asymmetric Digital Subscriber Line (ADSL) service. Also known as Universal ADSL, G.Lite makes it possible to have Internet connections to home and business computers at up to 1.5 Mbps (millions of bits per second) over regular phone lines. Even at the lowest downstream rate generally offered of 384 Kbps (thousands of bits per second), G.Lite is about seven times faster than regular phone service with a V.90 modem and three times faster than an Integrated Services Digital Network (ISDN) connection. Upstream speeds from the computer are at up to 128 Kbps. (Theoretical speeds for ADSL are much higher, but the data rates given here are what is realistically expected.)
With G.Lite, your computer's analog-to-digital modem is replaced with an "ADSL modem." and the transmission from the phone company is digital rather than the analog tranmission of "plain old telephone service." G.Lite is also known as "splitterless DSL" because, unlike other DSL technologies, it does not require that a technician come to install a splitter, a device that separates voice from data signals, at the home or business (sometimes referred to as "the truck roll").
The G.Lite standard was developed by the Universal ADSL Working Group, whose members include major phone companies in the U.S. and globally, including Ameritech, Bell Atlantic, BellSouth, GTE, MCI, USWest, Sprint, SBC Communications, Deutsche Telekom, France Telecom, British Telecommunications, Singapore Telecom, and Nippon Telegraph and Telephone. Microsoft, Intel, and Compaq are also represented in the Working Group.
A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes.
In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server and a firewall server. A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.
GGSN (Gateway GPRS Service Node)
A system that acts as a data gateway between 2.5G and 3G mobile networks and an IP network such as the Internet.
GSM (Global System for Mobile Communication)
GSM (Global System for Mobile Communication) is a digital mobile telephone system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephone technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band.
HDLC (High-level Data Link Control)
HDLC is a group of protocols or rules for transmitting data between network points (sometimes called nodes). In HDLC, data is organized into a unit (called a frame) and sent across a network to a destination that verifies its successful arrival. The HDLC protocol also manages the flow or pacing at which data is sent. HDLC is one of the most commonly-used protocols in what is layer 2 of the industry communication reference model called Open Systems Interconnection (OSI). (Layer 1 is the detailed physical level that involves actually generating and receiving the electronic signals. Layer 3 is the higher level that has knowledge about the network, including access to router tables that indicate where to forward or send data. On sending, programming in layer 3 creates a frame that usually contains source and destination network addresses. HDLC (layer 2) encapsulates the layer 3 frame, adding data link control information to a new, larger frame.
HDSL (High-bit-rate Digital Subscriber Line)
HDSL, one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is available in both directions. HDSL can carry as much on a single wire of twisted-pair cable as can be carried on a T1 line (up to 1.544 Mbps) in North America or an E1 line (up to 2.048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T1 or E1 connection.
The Home Location Register (HLR) is the main database of permanent subscriber information for a mobile network. The HLR is an integral component of CDMA (code division multiple access), TDMA (time division multiple access), and GSM (Global System for Mobile communications) networks. Maintained by the subscriber's home carrier (or the network operator where the user initiated the call), the HLR contains pertinent user information, including address, account status, and preferences. The HLR interacts with the Mobile Switching Center (MSC), which is a switch used for call control and processing. The MSC also serves as a point-of-access to the Public Switched Telephone Network (PSTN - the fixed network). The third integral element is the Visiting Location Register (VLR), which maintains temporary user information (such as current location) to manage requests from subscribers who are out of the area covered by their home system.
When a user initiates a call, the switching equipment determines whether or not the call is coming from the device's home area. If the user is out of the home area, the area VLR sends out a request for information required to process the call. An MSC queries the HLR identified by the call for information, which it relays to the appropriate MSC, which in turn relays it to the VLR. The VLR sends routing information back to the MSC which allows it to find the station where the call originated, and, finally, the mobile device to connect. Communications between the elements are based on Signaling System (SS7) protocols and signaling.
Also called an IXC ( IntereXchange Carrier). An interexchange carrier is a telephone company that provides connections between local exchanges in different geographic areas. IECs provide interLATA service as described in the Telecommunications Act of 1996. They're commonly referred to as "long-distance carriers." IECs include AT&T, MCI, Sprint, and others.
A standard specified by the 3GPP organization and embraced by others, which defines a generic architecture for offering VoIP, and multimedia services in both wireless and wireline networks. An example service provided by the IMS architecture includes voice, picture, text and video messaging. Artesyn offers controller boards and line card solutions to serve this application.
In information technology and on the Internet, infrastructure is the physical hardware used to interconnect computers and users. Infrastructure includes the transmission media, including telephone lines, cable television lines, and satellites and antennas, and also the routers, aggregators, repeaters, and other devices that control transmission paths. Infrastructure also includes the software used to send, receive, and manage the signals that are transmitted.
In some usages, infrastructure refers to interconnecting hardware and software and not to computers and other devices that are interconnected. However, to some information technology users, infrastructure is viewed as everything that supports the flow and processing of information.
The Internet, sometimes called simply "the Net," is a worldwide system of computer networks - a network of networks in which users at any one computer can, if they have permission, get information from any other computer (and sometimes talk directly to users at other computers). It was conceived by the Advanced Research Projects Agency (ARPA) of the U.S. government in 1969 and was first known as the ARPANET. The original aim was to create a network that would allow users of a research computer at one university to be able to "talk to" research computers at other universities. A side benefit of ARPANet's design was that, because messages could be routed or rerouted in more than one direction, the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster.
Today, the Internet is a public, cooperative, and self-sustaining facility accessible to hundreds of millions of people worldwide. Physically, the Internet uses a portion of the total resources of the currently existing public telecommunication networks. Technically, what distinguishes the Internet is its use of a set of protocols called TCP/IP (for Transmission Control Protocol/Internet Protocol). Two recent adaptations of Internet technology, the intranet and the extranet, also make use of the TCP/IP protocol. For many Internet users, electronic mail (e-mail) has practically replaced the Postal Service for short written transactions. Electronic mail is the most widely used application on the Net. You can also carry on live "conversations" with other computer users, using Internet Relay Chat (IRC). More recently, Internet telephony hardware and software allows real-time voice conversations.
The most widely used part of the Internet is the World Wide Web (often abbreviated "WWW" or called "the Web"). Its outstanding feature is hypertext, a method of instant cross-referencing. In most Web sites, certain words or phrases appear in text of a different color than the rest; often this text is also underlined. When you select one of these words or phrases, you will be transferred to the site or page that is relevant to this word or phrase. Sometimes there are buttons, images, or portions of images that are "clickable." If you move the pointer over a spot on a Web site and the pointer changes into a hand, this indicates that you can click and be transferred to another site.
Using the Web, you have access to millions of pages of information. Web browsing is done with a Web browser, the most popular of which are Microsoft Internet Explorer and Netscape Navigator. The appearance of a particular Web site may vary slightly depending on the browser you use. Also, later versions of a particular browser are able to render more "bells and whistles" such as animation, virtual reality, sound, and music files, than earlier versions.
The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet. When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address. Any packet is sent first to a gateway computer that understands a small part of the Internet. The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighborhood or domain. That gateway then forwards the packet directly to the computer whose address is specified.
Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different route across the Internet. Packets can arrive in a different order than the order they were sent in. The Internet Protocol just delivers them. It's up to another protocol, the Transmission Control Protocol (TCP) to put them back in the right order.
IP is a connectionless protocol, which means that there is no continuing connection between the end points that are communicating. Each packet that travels through the Internet is treated as an independent unit of data without any relation to any other unit of data. (The reason the packets do get put in the right order is because of TCP, the connection-oriented protocol that keeps track of the packet sequence in a message.) In the Open Systems Interconnection (OSI) communication model, IP is in layer 3, the Networking Layer. The most widely used version of IP today is Internet Protocol Version 4 (IPv4). However, IP Version 6 (IPv6) is also beginning to be supported. IPv6 provides for much longer addresses and therefore for the possibility of many more Internet users. IPv6 includes the capabilities of IPv4 and any server that can support IPv6 packets can also support IPv4 packets.
An IP telephone is a telephone that transports voice over a network using data packets instead of circuit switched connections over voice only networks.
IP PBX (Internet Protocol Private Branch eXchange)
An enterprise-scale telephone switch that enables users of IP telephones (such as H.323 clients, SIP Clients, etc.) to make Voice over IP telephone calls to other IP phones or phones on the public switched telephone network. Most IP PBXs can also switch traditional voice traffic.
ISDN (Integrated Services Digital Network)
ISDN is a set of CCITT/ITU standards for digital transmission over ordinary telephone copper wire as well as over other media. Home and business users who install an ISDN adapter (in place of a modem) can see highly-graphic Web pages arriving very quickly (up to 128 Kbps). ISDN requires adapters at both ends of the transmission so your access provider also needs an ISDN adapter. ISDN is generally available from your phone company in most urban areas in the United States and Europe. There are two levels of service: the Basic Rate Interface (BRI), intended for the home and small enterprise, and the Primary Rate Interface (PRI), for larger users. Both rates include a number of B-channels and a D-channels. Each B-channel carries data, voice, and other services. Each D-channel carries control and signaling information.
The Basic Rate Interface consists of two 64 Kbps B-channels and one 16 Kbps D- channel. Thus, a Basic Rate user can have up to 128 Kbps service. The Primary Rate consists of 23 B-channels and one 64 Kpbs D-channel in the United States or 30 B-channels and 1 D-channel in Europe. Integrated Services Digital Network in concept is the integration of both analog or voice data together with digital data over the same network. Although the ISDN you can install is integrating these on a medium designed for analog transmission, broadband ISDN (BISDN) will extend the integration of both services throughout the rest of the end-to-end path using fiber optic and radio media. Broadband ISDN will encompass frame relay service for high-speed data that can be sent in large bursts, the Fiber Distributed-Data Interface (FDDI), and the Synchronous Opical Network (SONET). BISDN will support transmission from 2 Mbps up to much higher, but as yet unspecified, rates.
ISP (Internet Service Provider)
An ISP (Internet service provider) is a company that provides individuals and other companies access to the Internet and other related services such as Web site building and virtual hosting. An ISP has the equipment and the telecommunication line access required to have a point-of-presence on the Internet for the geographic area served. The larger ISPs have their own high-speed leased lines so that they are less dependent on the telecommunication providers and can provide better service to their customers.
In international English outside the U.S., the equivalent usage is "kbps" or "kbits s-1." In the U.S., Kbps stands for kilobits per second (thousands of bits per second) and is a measure of bandwidth (the amount of data that can flow in a given time) on a data transmission medium. Higher bandwidths are more conveniently expressed in megabits per second (Mbps, or millions of bits per second) and in gigabits per second (Gbps, or billions of bits per second).
A local area network (LAN) is a group of computers and associated devices that share a common communications line or wireless link and typically share the resources of a single processor or server within a small geographic area (for example, within an office building). Usually, the server has applications and data storage that are shared in common by multiple computer users. A local area network may serve as few as two or three users (for example, in a home network) or many as thousands of users (for example, in an FDDI network).
LATA (Local Access and Transport Area)
LATA is a term in the U.S. for a geographic area covered by one or more local telephone companies, which are legally referred to as local exchange carriers (LECs). A connection between two local exchanges within the LATA is referred to as intraLATA. A connection between a carrier in one LATA to a carrier in another LATA is referred to as interLATA. InterLATA is long-distance service. The current rules for permitting a company to provide intraLATA or interLATA service (or both) are based on the Telecommunications Act of 1996.
LEC is the term for a public telephone company in the U.S. that provides local service. Some of the largest LECs are the Bell operating companies (BOCs) which were grouped into holding companies known collectively as the regional Bell operating companies (RBOCs) when the Bell System was broken up by a 1983 consent decree. In addition to the Bell companies, there are a number of independent LECs, such as GTE.
LEC companies are also sometimes referred to as "telcos." A "local exchange" is the local "central office" of an LEC. Lines from homes and businesses terminate at a local exchange. Local exchanges connect to other local exchanges within a local access and transport area (LATA) or to interexchange carriers (IXCs) such as long-distance carriers AT&T, MCI, and Sprint.
Linux (often pronounced LIH-nuhks with a short "i") is a Unix-like operating system that was designed to provide personal computer users a free or very low-cost operating system comparable to traditional and usually more expensive Unix systems. Linux has a reputation as a very efficient and fast-performing system. Linux's kernel (the central part of the operating system) was developed by Linus Torvalds at the University of Helsinki in Finland. To complete the operating system, Torvalds and other team members made use of system components developed by members of the Free Software Foundation for the GNU Project.
Linux is a remarkably complete operating system, including a graphical user interface, an X Window System, TCP/IP, the Emacs editor, and other components usually found in a comprehensive Unix system. Although copyrights are held by various creators of Linux's components, Linux is distributed using the Free Software Foundation's copyleft stipulations that mean any modified version that is redistributed must in turn be freely available.
Unlike Windows and other proprietary systems, Linux is publicly open and extendible by contributors. Because it conforms to the Portable Operating System Interface standard user and programming interfaces, developers can write programs that can be ported to other operating systems. Linux comes in versions for all the major microprocessor platforms including the Intel, PowerPC, Sparc, and Alpha platforms. It's also available on IBM's S/390. Linux is distributed commercially by a number of companies. A magazine, Linux Journal, is published as well as a number of books and pocket references.
Linux is sometimes suggested as a possible publicly-developed alternative to the desktop predominance of Microsoft Windows. Although Linux is popular among users already familiar with Unix, it remains far behind Windows in numbers of users. However, its use in the business enterprise is growing.
Mbps stands for millions of bits per second or megabits per second and is a measure of bandwidth (the total information flow over a given time) on a telecommunications medium. Depending on the medium and the transmission method, bandwidth is also sometimes measured in the Kbps (thousands of bits or kilobits per second) range or the Gbps (billions of bits or gigabits per second) range.
A megabit is a million binary pulses, or 1,000,000 (that is, 106) pulses (or "bits"). For example, a U.S. phone company T-carrier system line is said to sustain a data rate of 1.544 megabits per second. Megabits per second is usually shortened to Mbps.
Some sources define a megabit to mean 1,048,576 (that is, 220) bits. Although the bit is a unit of the binary number system, bits in data communications are discrete signal pulses and have historically been counted using the decimal number system. For example, 28.8 kilobits per second (Kbps) is 28,800 bits per second. Because of computer architecture and memory address boundaries, bytes are always some multiple or exponent of two
A media gateway is a network element that provides conversion between the audio signals carried on telephone circuits and data packets carried over the Internet or over other packet networks.
Megaco (MEdia GAteway COntrol)
Also referred to as H.248, it is a standard specifying the interface between a Media Gateway Controller and Media Gateways.
MGCP (Media Gateway Control Protocol)
MGCP, also known as H.248 and Megaco, is a standard protocol for handling the signaling and session management needed during a multimedia conference. The protocol defines a means of communication between a media gateway, which converts data from the format required for a circuit-switched network to that required for a packet-switched network and the media gateway controller. MGCP can be used to set up, maintain, and terminate calls between multiple endpoints. Megaco and H.248 refer to an enhanced version of MGCP
MicroTCA (Micro Telecommunications Computing Architecture)
MicroTCA is a draft system architecture specification that gained status as a subcommittee under the PICMG organization in October 2004. Conceptually, the MicroTCA allows Advanced Mezzanine Card (AdvancedMC or PICMG AMC.x) modules to be plugged into a system backplane. Key features of MicroTCA include small system footprint, low power, small module size, low cost and advanced management facilities.
Also sometimes called a Mobile Telephone Switching Office (MTSO) or Mobile Switching Office (MSO). A telephone switch, similar to a central office switch, that bridges a mobile telephone network with another telephone network such as the PSTN.
MSPP (Multi Service Provisioning Platform)
An access system that can provision a variety of different services such as TDM, Gigabit Ethernet, Wave Division Multiplexing (WDM), or Packet over SONET (PoS), to the end user. Artesyn provides Controller Boards and Line Cards to serve this application.
MTSO (Mobile Telephone Switching Office)
This is a Service Switching Point designed to provide switching services between a cellular and a wire-based telephone network. The MTSO provides the cellular customers connectivity to the standard phone network
In communication transmission systems, mux (pronounce muks, sometimes spelled "MUX") is an abbreviation for multiplexing, a device that sends multiple signals on a carrier channel at the same time in the form of a single, complex signal to another device that recovers the separate signals at the receiving end. The receiver is sometimes called a demux (or "DEMUX").
