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Glossary

BDR

Backup Designated Router: This is used in an OSPF network to

backup the designated router in case of failure.

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.

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.

BGP Identifier

This field contains a value that identifies the BGP

speaker. This is a random value chosen by the BGP router when sending
an OPEN message.

BGP neighbors

Two routers running BGP that begin a communication

process to exchange dynamic routing information; they use a TCP port at
Layer 4 of the OSI reference model. Specifically, TCP port 179 is used. Also
known as "BGP peers."

BGP peers

See: BGP neighbors.

BGP speaker

A router that advertises its prefixes or routes.

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.

binding

Configuring a Network layer protocol to use a certain frame type

on a LAN.

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.

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