ADTRAN L768 user manual Zip

Glosssary

2B+D

The Basic Rate Interface (BRI) in ISDN. A single ISDN circuit divided into two 64 kbps digital channels for voice or data and one 16 kbps channel for low speed data (up to 9,600 baud) and signalling. 2B+D is carried on one or two pairs of wires depending on the interface, the same wire pairs that today bring a single voice circuit into your home or office. See ISDN.

23B+D

In ISDN, also known as the Primary Rate Interface. A circuit with a wide range of frequencies that is divided in twenty-three 64 kbps paths for carrying voice, data, video, or other information simultaneously. It bears a remarkable similarity to today’s T1 link, except that T1 carries 24 voice channels. In ISDN, 23B+D gives twenty-three channels and one D channel for out-of-band signal- ling. 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 circuit consists of two pairs. One pair is used to send and one pair is used to receive. All trunk cir- cuits (long distance) are 4-wire. A 4-wire circuit delivers better reception, but also costs more. All local loop circuits (those coming from a Class 5 central of- fice to the subscriber’s phone system) are 2-wire, unless a 4-wire circuit is re- quested.

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 pro- vides Basic Rate Access with an operating frequency of 160 kbps and an infor- mation 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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