AT&T 7400 series, 7500 series, 7100 series, 2500 series, 7200 series manual Auxiliary Call Information

2-10COMMUNICATION SYSTEM NETWORKING — AN OVERVIEW

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the extension and RNX number to AAR for processing.

The UDP function is available on the System 75 and Generic 1 communications systems when either the UDP or PNA package is activated. On the DIMENSION, System 85, and Generic 2 communications systems, it becomes available only when the ETN (Standard Network) package is active. (On the DIMENSION, System 85, and Generic 2 systems, the UDP function is called RNX Steering.)

∙DACs and extensions — Regardless of the networking software that is active, callers may dial the dial access code (DAC) of an outgoing trunk group to access another switch in the network. When this happens, the internal dial plan uses the DAC to find an outgoing trunk group. The system sends the call to the next switch over the trunk group that the DAC designates.

Note that DAC dialing and AAR feature-access-code dialing are not compatible with DCS.

Auxiliary Call Information

Certain information can be associated with a call to help the switch determine how best to route it. This information consists of four parameters: the conditional call routing count, the facility restriction level (FRL), the partition of the originating call, and the bearer capability. These parameters influence how AAR/ARS routes a call:

∙Conditional call routing count — Used to route AAR calls on the System 85 and Generic 2 communications system. It tracks the number of satellite hops (or other types of routes that might influence a call’s quality adversely) that have been used to route a call thusfar. The number of satellite hops is important because using satellite facilities too many times along a call’s route produces unacceptable delays in voice calls and seriously degrades the transmission quality. If the satellite hop count is equal to two or more, the switch chooses a high-quality, terrestrial facility to route the call. Note that the conditional call routing count is used during pattern selection to determine the call category for AAR calls on the System 85 and Generic 2.

∙Facility restriction level (FRL) — Used to select a route for both AAR and ARS calls on all communications systems. Each terminal and trunk is assigned an FRL (0-7) to help the switch determine how appropriate a particular facility is for a call. For a call to be completed over a particular facility, the FRL of the facility must be equal to or less than the FRL of the originating station or trunk. This is why important users are given FRLs of 7, and facilities that everyone can use are given FRLs of 0.

Note that the FRL associated with the line’s or trunk’s class of service is the default FRL for each call originating there. The default FRL can be raised when the caller enters an authorization code, the call has timed-out from a outgoing trunk’s queue (System 85 and Generic 2 only), the FRL associated with a trunk call (stored in the traveling class mark, see below) is higher than the trunk FRL, or the caller has dialed a 4- or 5-digit extension number and the call must be routed to another switch in the private network (System 85 and Generic 2 only).

∙Partition number — This parameter is used to route ARS calls when tenant services software is active. When communications system resources are shared among different companies, it becomes important for callers to use only those facilities that are allocated to them. The partition number (System 85 and Generic 2) or partition group number (System 75 and Generic 1) tells the system where the call originated so it can use allocated facilities to route the call. Note that the partition number is used in the System 85 and Generic 2 during pattern selection to determine the call category for ARS calls.