Page 575

536

Glossary

baud

Synonymous with bits per second (bps), if each signal element repre-

sents one bit. It is a unit of signaling speed equivalent to the number of sep-
arate signal elements transmitted per second.

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.

bearer service

Used by service providers to provide DS0 service to ISDN

customers. A DS0 is one 64k channel. An ISDN bearer service provides
either two DS0s, called two bearer channels, for a Basic Rate Interface (BRI),
or 24 DS0s, called a Primary Rate Interface (PRI).

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.

bidirectional shared tree

A method of shared tree multicast forwarding.

This method allows group members to receive data from the source or the
RP, whichever is closer. See also: RP (rendezvous point).

binary

A two-character numbering method that uses ones and zeros. The

binary numbering system underlies all digital representation of information.

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-band-

width technologies such as video. BISDN presently employs ATM tech-
nology along SONET-based transmission circuits, supplying data rates
between 155Mbps and 622Mbps and beyond. Contrast with N-ISDN. See
also: BRI, ISDN, and PRI.

www.sybex.com