CCNA Cisco Certified Network Associate Study Guide - FTP Server

668 Glossary
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.
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.
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.
data direct VCC A bidirectional point-to-point virtual control connection
(VCC) set up between two LECs in ATM and one of three data connections
defined by Phase 1 LAN Emulation. Because data direct VCCs do not guarantee
QoS, they are generally reserved for UBR and ABR connections. Compare
with: control distribute VCC and control direct VCC.