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Glossary

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crankback

In ATM, a correction technique used when a node somewhere

on a chosen path cannot accept a connection setup request, blocking the
request. The path is rolled back to an intermediate node, which then uses
GCAC to attempt to find an alternate path to the final destination.

CRC

cyclical redundancy check: A methodology that detects errors,

whereby the frame recipient makes a calculation by dividing frame contents
with a prime binary divisor and compares the remainder to a value stored in
the frame by the sending node. Contrast with: checksum.

crossover cable

Type of Ethernet cable that connects a switch to switch,

host to host, hub to hub, or switch to hub.

CSMA/CD

Carrier Sense Multiple Access/Collision Detect: A technology

defined by the Ethernet IEEE 802.3 committee. Each device senses the cable
for a digital signal before transmitting. Also, CSMA/CD allows all devices on
the network to share the same cable, but one at a time. If two devices
transmit at the same time, a frame collision will occur and a jamming pattern
will be sent; the devices will stop transmitting, wait a predetermined amount
of time, and then try to transmit again.

CSU

channel service unit: A digital mechanism that connects end-user

equipment to the local digital telephone loop. Frequently referred to along
with the data service unit as CSU/DSU. See also: DSU.

CSU/DSU

channel service unit/data service unit: Physical layer device used

in wide area networks to convert the digital signals to what is understood by
the provider's switch. A CSU/DSU is typically one device that plugs into a
RJ-45 jack, known as the demarcation location.

CTD

Cell Transfer Delay: For a given connection in ATM, the time period

between a cell exit event at the source user-network interface (UNI) and the
corresponding cell entry event at the destination. The CTD between these
points is the sum of the total inter-ATM transmission delay and the total
ATM processing delay.

cut-through frame switching

A frame-switching technique that flows

data through a switch so that the leading edge exits the switch at the output
port before the packet finishes entering the input port. Frames will be read,
processed, and forwarded by devices that use cut-through switching as
soon as the destination address of the frame is confirmed and the outgoing
port is identified.

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