ADTRAN Express 6120 Bedienerhandbuch PDF herunterladen (Seite 152)

Glossary

Glossary-12 Express 6100/6120 User Manual 61200176L1-1

paths for carrying voice, data, video, or other information simulta-

neously. It bears a remarkable similarity to today’s T1 link, except

thatT1 carries 24voice channels. In ISDN, 23B+Dgives twenty-three

channels and one D channel for out-of-bandsignalling. However, in

T1, signalling is handled in-band. See ISDN.

two-wire circuit

A transmission circuit composed of two wires, signal and ground,

used to both send and receive information. In contrast, a 4-wire cir-

cuitconsistsoftwopairs. Onepairis usedtosendandonepairisused

to receive. All trunk circuits (long distance) are 4-wire. A 4-wire cir-

cuit delivers better reception, but also costs more. All local loop cir-

cuits (those coming from a Class 5 central office to the subscriber’s

phone system) are 2-wire, unless a 4-wire circuit is requested.

U-interface

A twisted pair subscriber loop that connects the NT1 reference point

to the ISDN network, as defined in the I.411 Recommendation. This

interface provides Basic Rate Access with an operating frequency of

160kbpsandan informationrateof144kbps. UnderU.S.regulations,

this also marks the line of demarcation between customer-owned

equipment and the public network.

ZIP

Zone Information Protocol. The AppleTalk session-layer protocol

used tomaintain and discover theinternet-wide mapping of network

number ranges to zone names.

Zombie Routes

Routes that have been identified by the router to be deleted. They re-

main inthe router’s route table for a specified amount oftime with an

infinite metric so that all other routers willlearn of this router’s inten-

tion to delete them.

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ADTRAN Express 6120 Bedienerhandbuch Seite 152