ADTRAN 1204006L1 Manual de usuario descargar pdf (Pagina 182)

Appendix D. Glossary

D-2 Express 5210 User Manual 61200208L1-1

the frame relay frame off each LAN frame, and passes the LAN frame on to the

end device. Bridges are generally used to connect LAN segments to other LAN

segments or to a WAN. They route traffic on the Level 2 LAN protocol (e.g. the

Media Access Control address), which occupies the lower sub-layer of the LAN

OSI data link layer. See also router.

CCITT

Consultive Committee for International Telephony and Telegraphy. A standards orga-

nization that devises and proposes recommendations for international commu-

nications. See also ANSI.

carrier detect. A signal generated by a modem or DSU/CSU. CD indicates the

presence of a carrier signal on a communications link.

clocking

An oscillator-generated signal that provides a timing reference for a transmis-

sion link. A clock provides signals used in a transmission system to control the

timing of certain functions. The clock has two functions, (1) to generate periodic

signals for synchronization and (2) to provide a time base.

CPE

customer premises equipment. All telecommunications terminal equipment

located on the customer premises, including telephone sets, private branch

exchanges (PBXs), data terminals, and customer-owned coin-operated tele-

phones.

CRC

cyclic redundancy check. A computational means to ensure the accuracy of frames

transmitted between devices in a frame relay network. The mathematical func-

tion is computed, before the frame is transmitted, at the originating device. Its

numerical value is computed based on the content of the frame. This value is

compared with a recomputed value of the function at the destination device. See

also FCS.

See CTS.

CSU

channel service unit. A device used to connect a digital phone line (T1 or

Switched 56 line) coming in from the phone company to either a multiplexer,

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ADTRAN 1204006L1 Manual de usuario Pagina 182