B-8
Appendix B: Glossary
C
C-bit Parity A framing format for E3- and T3-carrier lines. C-bit parity creates a block of
unmultiplexed data that uses the C-bit to signal framing.
CA Certificate Authority. A trusted third-party that verifies the identity of two
parties that want to communicate with one another. CAs are responsible for
generating, distributing, and revoking digital authentication certificates. Veri-
Sign is an example of a CA.
CAP Carrierless Amplitude/Phase. An ADSL modulation technique that divides the
available bandwidth into three channels: analog voice over 0-4 kHz, upstream
traffic over 25-160 kHz, and downstream traffic over 240 kHz-1.5 MHz. By
creating three widely separated channels, CAP minimizes interference
between the channels on one line and different lines. See also ADSL and DMT.
CAR Committed Access Rate. A QoS mechanism for policing traffic. You can set
the classification for packets, limit the bandwidth according to the traffic
classification, and then set parameters for how traffic is to be handled in the
event that congestion matches or exceeds the set rate limit. See also QoS.
CAST-128 Carlisle Adams and Stanford Tavares -128. A symmetric encryption algorithm
supported by IPSec, the industry standard for VPNs. CAST-128 is a block
cipher with a varying key size up to 128 bits. See also IPSec and VPN.
CBQ Class-Based Queuing. A QoS mechanism that is used to avoid traffic conges-
tion across a WAN line. CBQ is an open packet-scheduling algorithm that
enables different queues to be set up for different traffic classes. Bandwidth
can then be statically assigned to each queue. See also QoS.
CBR
Constant Bit Rate. A quality of service mechanism that specifies a constant data
output rate. CBR is useful for streaming multimedia content on limited capacity
channels because the maximum bit rate matters, rather than the average bit
rate. CBR could take advantage of all of the capacity.
See also
QoS.
CCP Compression Control Protocol. Part of the PPP suite, CCP configures, enables,
and disables data compression algorithms on both ends of a point-to-point
link. For more information about CCP, see RFC 1962 (at http://www.ietf.org/
rfc/rfc1962.txt).
CCITT Consultative Committee for International Telegraph and Telephone. The
CCITT, now known as the International Telecommunications Union–Telecom-
munications Services Sector (ITU-T), is an international body that fosters
cooperative standards for telecommunications equipment and systems.
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