D-3
Cisco ONS 15454 Installation and Operations Guide
November 2001
AppendixD Glossary
Bridge
Device that connects and passes packets between two network segments that use the same
communications protocol. In general, a bridge will filter, forward, or flood an incoming frame based on
the MAC address of that frame.
Broadcast
Data packet that will be sent to all nodes on a network. Broadcasts are identified by a broadcast address.
Compare with multicast and unicast. See also Broadcast address.
Broadcast address
Special address reserved for sending a message to all stations. Gen erally, a broadcast address is a MAC
destination address of all ones.
Broadcast storm
Undesirable network event in which many broadcasts are sent simu ltane ously a cross all netw or k
segments. A broadcast storm uses substantial network bandwidth and, t ypicall y, causes network
time-outs.
Bus
Common physical signal path composed of wires or other media across which signals can be sent from
one part of a computer to another.
C
C2 byte
The C2 byte is the signal label byte in the STS path overhead. This byte tells the equipment what the
SONET payload envelope contains and how it is constructed.
Collision
In Ethernet, the result of two nodes transmitting simultaneously. The frames from each device impact
and are damaged when they meet on the physical media.
Concatenation
A mechanism for allocating contiguous bandwidth for payload transport. Through the use of
Concatenation Pointers, multiple OC-1s can be linked together to p rovide contiguous bandwidth through
the network, from end to end.
Crosspoint
A set of physical or logical contacts that operate together to extend the sp eec h an d signa l ch an ne ls in a
switching network.
CTAG
Correlation Tag. A unique identifier given to each input command by the TL1 operator. When the ONS
15454 system responds to a specific command, it includes the c omma nd ’s CTAG in the reply. This
eliminates discrepancies about which response corresponds to wh ich comm a nd.