AT&T DS1/DMi/ISDN-PRI manual Grs, Hdlc

GL-10	GLOSSARY
final trunk		A last-choice trunk group that receives overflow traffic and may receive first-
group		route traffic. See also trunk group.
facilities		An assigned number that determines both the kinds of calls that can be made and
restriction level		the kinds of facilities (trunks) that can be used when calls are routed via
(FRL)		Automatic Alternate Routing (AAR). See also alternate facilities restriction
		level.
first-choice		The group of trunks on a communications system that is chosen first for a
trunk group		particular call. See also trunk group.
fixed-loss plan		An end-to-end office-transmission loss plan for the public network in which all
		connecting trunks and end offices are digital. For all tandem connections, a
		fixed loss of 6 dB is inserted in the receive path of each end office.

Flexible Assignment of BX.25 (DCIU/SCI) Signaling Ports

foreign exchange (FX)

frame

FRL

functional signaling

FX

Generalized

Route Selection

(GRS)

glare

A feature that allows ports normally reserved for an application not needed for that communications system to be used for another application. In the initial implementation of data-communications interface unit switch communications interface (DCIU-SCI) signaling ports in System 75 and System 85, certain such ports were reserved for specific applications. See also BX.25.

A central office (CO) other than the one providing local access to the public network.

One of several segments of an analog or digital signal that has a repetitive characteristic. For example, in a time-division multiplexed (TDM) system a frame is a sequence of time slots, each containing a sample from one of the channels served by the multiplex system. The frame is repeated at the sampling rate, and each channel occupies the same sequence position in successive frames. See also D4 framing format and extended superframe framing format.

See facilities restriction level.

The signaling method used to request specific operations, such as call setup and call conferencing. See also stimulus signaling.

See foreign exchange.

An enhancement to Automatic Alternate Routing/Automatic Route selection (AAR/ARS) that performs routing based on call attributes, such as bearer- capability classes (BCC), in addition to the address and facilities restriction level (FRL), thus facilitating a Uniform Dial Plan (UDP) that is independent of the type of call being placed.

The simultaneous seizure of a two-way trunk by two communications systems, resulting in a standoff.

GRS	See Generalized Route Selection.
HDLC	See high-level data link control.
high-level data	A standard bit-oriented protocol, developed by the International Standards
link control	Organization (ISO), in which control information is always placed in the same
(HDLC)	position and specific bit patterns used for control differ from those used in
	representing data, so that errors are less likely to occur.