Cisco 12004 GSR Справочный материал - Страница 10

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20614 Cisco Installing and Maintaining Routers Part 4: 12000 GSR Series and XS5032 Modules

Cyclic redundancy check. Error−checking technique in which the frame recipient calculates a remainder by

dividing frame contents by a prime binary divisor and compares the calculated remainder to a value stored in

the frame by the sending node.

CSC

Clock and scheduler card

CSU

Channel Service Unit. Digital interface device that connects end−user equipment to the local digital telephone

loop. Often referred to together with DSU, as CSU/DSU.

CxBus

Cisco Extended Bus. Data bus for interface processors on Cisco 7000 series routers.

Data Circuit−terminating Equipment (DCE)

data circuit−terminating equipment (ITU−T expansion). Devices and connections of a communications

network that comprise the network end of the user−to−network interface. The DCE provides a physical

connection to the network, forwards traffic, and provides a clocking signal used to synchronize data

transmission between DCE and DTE devices. Modems and interface cards are examples of DCE.

Data Service Unit (DSU)

data service unit. Device used in digital transmission that adapts the physical interface on a DTE device to a

transmission facility such as T1 or E1. The DSU is also responsible for such functions as signal timing. Often

referred to together with CSU, as CSU/DSU.

DB−25 connector

A 25−pin connector used by parellel ports data bus connector

dBus

Diagnostic bus

dial−on−demand routing (DDR)

dial−on−demand routing. Technique whereby a router can automatically initiate and close a circuit−switched

session as transmitting stations demand. The router spoofs keepalives so that end stations treat the session as

active. DDR permits routing over ISDN or telephone lines using an external ISDN terminal adaptor or

modem.

DIMM

dual in−line memory module

DRAM