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
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