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Glossary

character mode connections

Character mode connections are typically

terminated at the access server and include Telnet and console connections.

checksum

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

culated from a series of values taken through a sequence of mathematical
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.

CIR

Committed Information Rate: Averaged over a minimum span of time

and measured in bps, a Frame Relay network's agreed-upon minimum rate
of transferring information.

circuit switching

Used with dial-up networks such as PPP and ISDN.

Passes data, but needs to set up the connection first--just like making a
phone call.

Cisco FRAD

Cisco Frame-Relay Access Device: A Cisco product that sup-

ports Cisco IPS Frame Relay SNA services, connecting SDLC devices to
Frame Relay without requiring an existing LAN. May be upgraded to a fully
functioning multiprotocol router. Can activate conversion from SDLC to
Ethernet and Token Ring, but does not support attached LANs.
See also: FRAD.

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