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Glossary

CGMP

Cisco Group Management Protocol: A proprietary protocol

developed by Cisco. The router uses CGMP to send multicast membership
commands to Catalyst switches.

channelized E-1

Operating at 2.048Mpbs, an access link that is sectioned

into 29 B-channels and one D-channel, supporting DDR, Frame Relay, and
X.25. Compare with: channelized T-1.

channelized T-1

Operating at 1.544Mbps, an access link that is sectioned

into 23 B-channels and one D-channel of 64Kbps each, where individual
channels or groups of channels connect to various destinations, supporting
DDR, Frame Relay, and X.25. Compare with: channelized E-1.

CHAP

Challenge Handshake Authentication Protocol: Supported on lines

using PPP encapsulation, it is a security feature that identifies the remote end,
helping keep out unauthorized users. After CHAP is performed, the router
or access server determines whether a given user is permitted access. It is a
newer, more secure protocol than PAP. Compare with: PAP.

checksum

A test for ensuring the integrity of sent data. It is a number

calculated from a series of values taken through a sequence of mathemat-
ical functions, typically placed at the end of the data from which it is
calculated, and then recalculated at the receiving end for verification.
Compare with: CRC.

choke packet

When congestion exists, it is a packet sent to inform a trans-

mitter that it should decrease its sending rate.

CIDR

Classless Interdomain Routing: A method supported by classless

routing protocols, such as OSPF and BGP4, based on the concept of ignoring
the IP class of address, permitting route aggregation and VLSM that enable
routers to combine routes in order to minimize the routing information that
needs to be conveyed by the primary routers. It allows a group of IP net-
works to appear to other networks as a unified, larger entity. In CIDR, IP
addresses and their subnet masks are written as four dotted octets, followed
by a forward slash and the numbering of masking bits (a form of subnet
notation shorthand). See also: BGP4.

CIP

Channel Interface Processor: A channel attachment interface for use in

Cisco 7000 series routers that connects a host mainframe to a control unit.
This device eliminates the need for an FBP to attach channels.

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