ADTRAN Express 4120 User Manual

Page 190

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Glossary

Glossary-8

Express 4110/4120 User Manual

61200176L3-1

4-wire. A 4-wire circuit delivers better reception, but also costs more. All local loop

circuits (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 net-

work, as defined in the I.411 Recommendation. This interface provides Basic Rate Ac-

cess with an operating frequency of 160 kbps and an information rate of 144 kbps.

Under U.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 to maintain

and discover the internet-wide mapping of network number ranges to zone names.

Zombie Routes

Routes that have been identified by the router to be deleted. They remain in the router’s

route table for a specified amount of time with an infinite metric so that all other routers

will learn of this router’s intention to delete them.

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