B

B8ZS

Binary 8-Zero Substitution: A line-code type, interpreted at the remote end of the connection, that uses a special code substitution whenever eight consecutive zeros are transmitted over the link on T1 and E1 circuits. This technique assures ones density independent of the data stream. Also known as bipolar 8-zero substitution. Contrast with: AMI. See also: ones density.

backbone

The basic portion of the network that provides the primary path for traffic sent to and initiated from other networks.

back end

A node or software program supplying services to a front end. See also: client, front end, and server.

bandwidth

The gap between the highest and lowest frequencies employed by network signals. More commonly, it refers to the rated throughput capacity of a network protocol or medium.

baseband

A feature of a network technology that uses only one carrier frequency, for example Ethernet. Also named “narrowband.” Compare with: broadband.

baud

Synonymous with bits per second (bps), if each signal element represents one bit. It is a unit of signaling speed equivalent to the number of separate signal elements transmitted per second.

Bc

Committed Burst. Negotiated tariff in Frame Relay networks. The maximum amount of data (in bits) that a Frame Relay network is committed to accept and transmit at the CIR. See also CIR.

B channel

Bearer channel: A full-duplex, 64Kbps channel in ISDN that transmits user data. Compare with: D channel, E channel, and H channel.

beacon

An FDDI device or Token Ring frame that points to a serious problem with the ring, such as a broken cable. The beacon frame carries the address of the station thought to be down. See also: failure domain.

BDR

(Backup Designated Router) OSPF elects a designated router and a backup designated router for route updates.

BECN

Backward Explicit Congestion Notification: BECN is the bit set by a Frame Relay network in frames moving away from frames headed into a congested path. A DTE that receives frames with the BECN may ask higher- level protocols to take necessary flow control measures. Compare with: FECN.

BGP4

BGP Version 4: Version 4 of the interdomain routing protocol most commonly used on the Internet. BGP4 supports CIDR and uses route-counting mechanisms to decrease the size of routing tables. See also: CIDR.

binary

A two-character numbering method that uses ones and zeros. The binary numbering system underlies all digital representation of information.

binding

The process of establishing communications between the protocol device driver and the network interface card driver.

BIP

Bit Interleaved Parity: A method used in ATM to monitor errors on a link, sending a check bit or word in the link overhead for the previous block or frame. This allows bit errors in transmissions to be found and delivered as maintenance information.

BISDN

Broadband ISDN: ITU-T standards created to manage high- bandwidth technologies such as video. BISDN presently employs ATM technology along SONET-based transmission circuits, supplying data rates between 155Mbps and 622Mbps and beyond. Contrast with N-ISDN. See also: BRI, ISDN, and PRI.

bit-oriented protocol

Regardless of frame content, the class of Data Link layer communication protocols that transmits frames. Bit-oriented protocols, as compared with byte-oriented, supply more efficient and trustworthy, full-duplex operation. Compare with: byte-oriented protocol.

border gateway

A router that facilitates communication with routers in different autonomous systems.

BPDU

Bridge Protocol Data Unit: A Spanning Tree Protocol initializing packet that is sent at definable intervals for the purpose of exchanging information among bridges in networks.

BRI

Basic Rate Interface: The ISDN interface that facilitates circuit-switched communication between video, data, and voice; it is made up of two B channels 64Kbps each) and one D channel (16Kbps). Compare with: PRI. See also: BISDN, ISN.

bridge

A device for connecting two segments of a network and transmitting packets between them. Both segments must use identical protocols to communicate. Bridges function at the Data Link layer, Layer 2 of the OSI reference model. The purpose of a bridge is to filter, send, or flood any incoming frame, based on the MAC address of that particular frame.

broadband

A transmission methodology for multiplexing several independent signals onto one cable. In telecommunications, broadband is classified as any channel with bandwidth greater than 4kHz (typical voice grade). In LAN terminology, it is classified as a coaxial cable on which analog signaling is employed. Also known as wideband. Contrast with: baseband.

broadcast

A data frame or packet that is transmitted to every node on a network. Broadcasts are known by their broadcast address, which is a destination address with all the bits turned on.

broadcast domain

A group of devices receiving broadcast frames initiating from any device within the group. Because they do not forward broadcast frames, broadcast domains are generally surrounded by routers.

broadcast storm

An undesired event on the network caused by the simultaneous transmission of any number of broadcasts across all network segments. Such an occurrence can overwhelm network bandwidth, resulting in time-outs.

buffer

A storage area dedicated to handling data while in transit. Buffers are used to receive/store sporadic deliveries of data bursts, usually received from faster devices, compensating for the variations in processing speed. Incoming information is stored until everything is received prior to sending data on. Also known as an information buffer.

bus topology

A linear LAN architecture in which transmissions from various stations on the network are reproduced over the length of the medium and are accepted by all other stations. Compare with: ring, star, and tree topologies.

bus

Any physical path, typically wires or copper, through which a digital signal can be used to send data from one part of a computer to another.

BUS

Broadcast and Unknown Server: In LAN emulation, the hardware or software responsible for resolving all broadcasts and packets with unknown (unregistered) addresses into the point-to-point virtual circuits required by ATM. See also: LEC, LECS, LES, and LANE.

BX.25

AT&T’s use of X.25. See also: X.25.

bypass mode

An FDDI and Token Ring network operation that deletes an interface.

bypass relay

A device that enables a particular interface in the Token Ring to be closed down and effectively taken off the ring.

byte-oriented protocol

Any type of data-link communication protocol that, in order to mark the boundaries of frames, uses a specific character from the user character set. These protocols have generally been superseded by bit-oriented protocols. Compare with: bit-oriented protocol.