B-11
Appendix B: Glossary
Console A terminal attached to a minicomputer, network device, or mainframe that is
used to configure and monitor the status of the system.
CoS Class of Service. A method of managing traffic in a network by grouping
similar types of traffic together and treating each group as a class with its own
level of service priority. See also QoS.
CPE Customer Premises Equipment. The public carrier access equipment that a
customer must purchase and maintain. This equipment is not maintained or
owned by the Local Exchange Carrier. Some examples of this equipment are
CSU/DSUs, modems and telephones.
CRC Cyclic Redundancy Checking. A method of checking for errors in data that is
transmitted between two devices. The sending device applies a 16- or 32-bit
polynomial to data, appends the resulting cyclic redundancy code to the data,
and then sends the data. The receiving device applies the same polynomial to
the data and checks the results against the appended results. If the two do not
match, an error has occurred during the transmission.
CRC4 A framing format supported by a separate framing channel in E1 technology.
CRC4 is based on the E1 frame format but includes additional error detection.
A checksum bit is included in all even frames: frames 0, 2, 4, 6, 8, 10, 12, and
14. A total of 8 checksum bits is used. See also E1 frame format.
Crossover Cable Also called a null-modem cable. A specially designed cable that allows a user
to connect two computers directly to each other via their communications
(RS-232) ports.
Crypto Map In a ProCurve Secure Router environment, a crypto map defines parame-
ters for the IKE and IPSec SA negotiation for a VPN. See also IKE, IPSec,
SA and VPN.
CSS Controlled Slip Second. An error designation that describes a one-second
interval containing one or more controlled slips. A controlled slip is the
replication or deletion of the payload bits of a DS1 or E1 frame, and may be
caused by a difference between the timing of a synchronous receiving terminal
and the received signal.
CSU Channel Service Unit. Used in carrier-line connections, the CSU is a device
that provides signal generation/regeneration. A CSU provides local loop equal-
ization, transient protection, isolation, and Central Office (CO) loopback
testing capability. In the United States and Canada, the CSU is sometimes
provided in conjunction with the DSU and referred to as the CSU/DSU. See
also DSU.
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