Binary/Bipolar Three Zero Substitution

A method of encoding a string of 3 zeros by inserting bipolar violations.

Binary 8-Zero Substitution

Line-code type, used on T1 and E1 circuits, in which a special code is substituted whenever 8 consecutive zeros are sent over the link. This code is then interpreted at the remote end of the connection. This technique guarantees ones density independent of the data stream. Sometimes called "bipolar 8-zero substitution."

The indirect routing of a call through a network because it is less expensive to do so. For example, a link between a central office and a main microwave or multiplex station, or between a ground satellite station, or submarine cable terminal and switching centre where forward distribution occurs.

LAN or WAN connectivity between subnets across a high-speed network. Often applied to a high-speed campus network, such as ATM OC-12 or Gigabit Ethernet, that interconnects lower-speed networks, such as ATM OC-3 or Fast Ethernet. Fibre optic cable is often used.

A network with a central cabling scheme linking it to other networks. Hosts on networks linked to the backbone can communicate with one another.

Routers designed to be used to construct backbone networks using leased lines. Typically do not have any built-in digital dial-up WAN interfaces.

Algorithmic process used for routing traffic that surmises information by assuming symmetrical network conditions. For example, if node A receives a packet from node B through intermediate node C, the backward-learning routing algorithm will assume that A can optimally reach B through C.

Balanced, Unbalanced

Device used for matching impedance between a balanced and an unbalanced line, usually twisted-pair and coaxial cable.

A circuit designed to allow only frequencies within a specific range to pass. The cut-off frequencies must be finite and nonzero. The band of frequencies between the cut-off frequencies is the passband.

A circuit's capacity to carry communications signals, measured by the range of frequencies (expressed in hertz) the circuit carries. (2) The information-carrying capacity of a computer or communications channel, such as a telephone line, measured in bits per second. (3) The range of frequencies available for signalling; the difference between the highest and lowest frequencies of a band, expressed in hertz.

Process of assigning bandwidth to users and applications served by a network. Involves assigning priority to different flows of traffic on how critical and delay-sensitive they are. This makes the best use of available bandwidth, and if the network becomes congested, lower-priority traffic can be dropped. Sometimes called "bandwidth allocation."

The submarine cable between Barcelona, Spain and Pisa, Italy.

The submarine cable between Barcelona, Spain and Genoa, Italy.

The submarine cable between Barcelona, Spain and Rome, Italy.

In cellular communications, and installation, located within a cell that houses the equipment needed to set up and complete calls on cellular phones, i.e. FM radio transmitter and receiver, antenna, and computer. The base station works with the subscriber's handset and the Mobile Switching Centre to complete a call.

In cellular communications, the component that consists of all radio transmission and reception equipment, it provides coverage to a geographic area, and is controlled by a Base Station Controller.

Describing the band of frequencies occupied by a signal below the point that the signal is modulated as an analogue carrier frequency. Also known as "narrowband."

A unit of modulation rate, equal to the maximum number of signal events or symbols that can be transmitted per second. A signal event is a change in an information-bearing signal or waveform, which represents some number of encoded bits. The term baud should not be used as a synonym for bits per second (though many people do) since at speeds above 2,400 bits per second multiple bits are sent in each baud and, therefore, the baud rate does not equal the bit rate.

Bulletin Board System

A computer system that functions as a centralized information source and message system for a particular group of users.

Committed Burst

Negotiated tariff metric in Frame Relay Internetworks. The maximum amount of data (in bits) that a Frame Relay Internetwork is committed to accept and transmit at the CIR.

Binary-Coded Decimal

A code compression scheme in which two binary bits replace the three zone bits and four binary bits replace the nine data bits.

Bose-Chaudhuri-Hocquenghem

A forward error correction technique with low-overhead, often used for videoconferencing as in H.261.

A B-channel is a "bearer" channel, one of the fundamental components of the ISDN interface. The B channel is circuit-switched and can carry 64,000bps of voice or data in either direction. Bundling is based on Digital Speed Interpolation (DSI), a technique used to squeeze more voice conversations onto a single line.

Broadband Digital Cross-Connect System

SONET DCS capable of cross-connecting DS-3, STS-1 and STS-3c signals.

Excess Burst

Negotiated tariff metric in Frame Relay Internetworks. The number of bits that a Frame Relay will attempt to transmit after Bc is accommodated. Be data is, in general, delivered with a lower probability than Bc data because Be data can be marked as DE by the network.

A condition where no data can pass on a Token Ring or fibre-distributed data interface (FDDI) network.

A specialized frame in token-passing networks, sent to indicate and recover from a break in the ring.

Token Ring process to recover the network when any attached station has sensed that the ring is inoperable because of a hard error Stations can withdraw from the ring if needed. A station detecting a ring failure upstream transmits (beacons) a special MAC frame used to isolate the location of the error using beacon transmit and beacon repeat modes.

Backward Explicit Congestion Notification

Bit set by a Frame Relay network in frames travelling in the opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request that higher-level protocols take flow control action as appropriate.

Best-Effort Delivery

Describes a network system that does not use a sophisticated acknowledgment system to guarantee reliable delivery of information.

Business Exchange Measured Service

A usage-sensitive rating structure for business local service in which business customers pay a reduced flat rate for access to the telephone network and a separate per-minute charge for their outgoing local calling. Incoming calls, long distance calls, operator-handled and directory assistance calls, and local calls internal to a business's own system are excluded.

Bit Error Rate

Ratio of received bits that contain errors.

Basic Encoding Rules

Rules for encoding data units described in the ISO ASN.1 standard.

The submarine cable between the U.S. and Bermuda.

Bit Error Rate Tester

Device that determines the BER on a given communications channel.

Ball Grid Array

Chip package

Border Gateway Protocol

Interdomain routing protocol that replaces EGP. BGP exchanges reachability information with other BGP systems.

BGP Version 4

Version 4 of the predominant inter-domain routing protocol used on the Internet. BGP4 supports CIDR and uses route aggregation mechanisms to reduce the size of routing tables.

Broadband Inter-Carrier Interface

ITU-T standard that defines the protocols and procedures needed for establishing, maintaining, and terminating broadband switched virtual connections between public networks.

Numbering system characterized by ones and zeros (1 = on, 0 = off).

The smallest entity of digital information possible.

Binary Hexadecimal

Method for converting binary files into ASCII for transmission by applications, such as email, that can only handle ASCII.

Bit Interleaved Parity

In ATM, a method used to monitor errors on a link. A check bit or word is sent in the link overhead for the previous block or frame. Bit errors in the payload can then be detected and reported as maintenance information.

Bipolar coding scheme originally developed for use in Ethernet. Clocking information is embedded into and recovered from the synchronous data stream without the need for separate clocking leads. The bi-phase signal contains no direct current energy.

A 2-state code where successive "1" signals alternate between positive and negative polarity. (2) Electrical characteristic denoting a circuit with both negative and positive polarity.

Broadband Integrated Services Digital Network

The new generation of ISDN which carries digital data, voice, and video over SONET networks. B-ISDN allows Asynchronous Transfer Mode (ATM) and Synchronous Transfer Mode (STM) services to operate on the same network.

Binary digit

Contraction of the term Binary digit

A form of Time Division Multiplexing (TDM) for synchronous protocols, including HDLC, SDLC, BiSync and X.25 Bit inter-leaving retains the sequence and number of bits, so that correct synchronization is achieved between both ends.

Routing term for an area of the Internetwork where packets enter, but do not emerge, due to adverse conditions or poor system configuration within a portion of the network.

Bell Labs Layered Space Time

Building Local Exchange Carrier

A company that supplies communications services to office blocks. A term used in the U.S. In Europe the term BSP (building service provider) is more commonly used.

Block Error Rate Test/Tester

A method or device used to measure the quality of the block transmission, the pattern of block transmission, and the number of block errors received. The figures obtained are used to compute the block error rate.

Binary Large Object

Massive image files to be moved across local area networks (LANs).

A collection of transmitted data that is treated as a complete and separate identity. Blocks typically have a specific address, control routing, and error checking data.

One or more bits in a 1-second window are in error (for DDS). Block size varies for other applications.

The total number of records, words, or characters contained in one block.

This term, when used with either error control or data compression protocols, refers to the number of characters to be sent at one time. If error control is used, the codes are sent immediately following this block.

In a switching system, a condition in which no paths are available to complete a circuit. The term is also used to describe a situation in which one activity cannot begin until another is completed.

Internal cooling fan used in larger router and switch chassis.

Bidirectional Line Switch Ring

SONET ring architecture that provides working and protection fibres between nodes. If the working fibre between nodes is cut, traffic is automatically routed onto the protection fibre.

A short-range wireless connection standard. Its aim is to link a wide range of computers, electronics and telecoms devices. The technology uses a low-power, two-way radio link, which is built into a microchip.

Broadband Network Interface

Broadband Network Module

Boundary Network Node

In SNA terminology, a subarean node that provides boundary function support for adjacent peripheral nodes. This support includes sequencing, pacing, and address translation.

Bell Operating Company

The local (or regional) telephone company that owns and operates lines to customer locations and Class 5 Central Office switches.

Bootstrap Protocol

Protocol used by a network node to determine the IP address of its Ethernet interfaces, in order to affect network booting.

Battery supply, Overvoltage protection, Ringing current, Supervision, Coding, Hybrid conversion, Testing

The functions required in any telephone line card.

Build-Operate-Transfer Agreement

Bypass

The ability of a station or port to be optically or electronically isolated from a ring network while maintaining the integrity of the ring. The direct connection to customer-premises equipment by an interexchange carrier (IC).

Break-Even Point

The usage level at which the total cost of a service with a high monthly fee and low per-minute costs becomes equal to the total cost of another service with a low monthly fee and high per-minute cost. The service with the high monthly fee is cheaper at usage levels above the BP.

Bridge Protocol Data Unit

Spanning-Tree Protocol hello packet that is sent out at configurable intervals to exchange information among bridges in the network.

Baseline Privacy Interface

Bits per second

The number of binary digits transmitted over a communications channel in one second. For example, Ethernet is a 10-Mbps network, Token Ring is a 4-Mbps or 16-Mbps network, and fibre-distributed data interface (FDDI) is a 100-Mbps network.

Bipolar Violation

A condition which occurs when an AMI-coded signal contains a pulse of the same polarity as the previous pulse and which is not part of a bipolar zero substitution code.

A specific BPV sequence purposely introduced to the local loop for network control.

The rate of erroneous received data bits to total received data bits. This rate excludes framing bits, CRC-6 bits, or data link bits.

Bipolar Violation Ratio

The number of accumulated BPVs in the last monitored interval divided by the number of bits in that interval. Any one second where there is an LOS condition is not included in this computation.

Basic Rate Access

BRA provides ISDN users with access to two 64Kbit/s data channels, It is defined in ITU-TS Recommendation I.420 which covers a 2B + D-channel where the B channel is a 64Kbit/s channel, and the D-channel is a 16Kbit/s signalling channel.

The submarine cable between Brazil and the Canary Islands.

Block Redundancy Check

The information added to a transmitted block to verify accuracy of data before it is accepted. Block check data is developed by the sender as a predefined function of information in the block. The receiver performs the same function on the received data, and compares the calculated and received block checks. The block is accepted only if the comparison is exact.

Bridge Relay Function

Basic Rate Interface

An ISDN subscriber line, consisting of two 64kbit/s B channels, or "bearer" channels, and one 16kbit/s D channel, used for both data and signalling purposes.

Device that connects and passes packets between two network segments that use the same communications protocol. Bridges operate at the data link layer (Layer 2) of the OSI reference model. In general, a bridge will filter, forward, or flood an incoming frame based on the MAC address of that frame.

A service or system requiring transmission channels capable of supporting rates greater than the ISDN primary rate or circuits that carry data at rates that range from 1.544 million bits per second (megabits) to billions of bits per second (gigabits). (2) LAN terminology: A coaxial cable on which analogue signalling is used. Also called wideband. (3) Telecommunications terminology: Any channel having a bandwidth greater than a voice-grade channel (4 kHz). (4) Transmission system that multiplexes multiple independent signals onto one cable.

A network that enables a device to transmit a large amount of information (including voice, data, and video) on the same cable over long distances.

Data packet that will be sent to all nodes on a network. Broadcasts are identified by a broadcast address.

Special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones.

Set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains are typically bounded by routers because routers do not forward broadcast frames.

Propagation of a search request to all network nodes if the location of a resource is unknown to the requester.

Undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs.

A device that combines the dynamic routing capability of an internetwork router with the ability of a bridge to interconnect local area networks.

The submarine cable between Brazil and the U.S.

Binary Synchronous Communication

Character-oriented data link layer protocol for half-duplex applications. A form of telecommunication line control that uses a standard set of transmission control characters and control character sequences, for binary synchronous transmission of binary-coded data between stations.

Branch Systems General License

A license which must be obtained by any organization seeking to link its own private network to the Public Switched Telephone Network (PSTN). A separate license must be held for each individual site.

Building Service Provider

A company that supplies communications services to office blocks. A term used in the Europe. In the U.S. the term BLEC (building local exchange carrier) is more commonly used.

Base Station Subsystem

Burst Tolerance

Parameter defined by the ATM Forum for ATM traffic management. For VBR connections, BT determines the size of the maximum burst of contiguous cells that can be transmitted.

Basic Telecommunications Access Method

An access method that supports read/write communications between remote devices.

A sequence of signals counted as one unit in accordance with some specific criterion or measure.

A method of transmitting data. When a device uses burst mode, it collects and sends data in a single high-speed transmission, rather than one character at a time.

Broadcast and Unknown Server

Multicast server used in ELANs that is used to flood traffic addressed to an unknown destination and to forward multicast and broadcast traffic to the appropriate clients.

A linear network topology. A bus network is a local area network (LAN) in which all workstations are connected to a single cable. All workstations receive all transmissions on the cable. Each workstation selects those transmissions addressed to it based on the address information contained in the transmission. A bus network is the simplest and most common LAN topology.

The lines over which a call is to be transmitted are already in use. Slow busy signals (60 times per minute) indicate the receiving telephone is busy or off-hook. Fast busy signals (120 times per minute) indicate that the network facilities are congested with too many calls.

A hand-carried test telephone used to monitor, dial, and talk on conventional analogue telephone lines. So named because the craft person could clip onto a telephone line and "butt in" to a conversation.

Bridge Group Virtual Interface

Broadband Wireless Access

A service providing two-way, broadband, data, voice, multimedia and information services using (mostly) millimetre wave radio links. BWA is similar to LMDS except that in most cases it excludes video broadcast as a service.

Broadband Switch Module

8 bits of data, also called an octet.

Process of storing numeric data with the least-significant byte first. Used for integers and addresses on devices with Intel microprocessors.

A technique which increases the speed of a digital stream by repeating bytes and transmitting them at a faster rate. This technique does not increase the information content of the stream.