Administrator's Guide

Features and technical reference
555-233-5061750 Issue 5 October 2002
Look-ahead routing
Look-Ahead Routing (LAR) allows the switch to reroute an outgoing ISDN call
that is not completing. The switch attempts to complete the call along a different
routing preference, or it tries the current routing preference a second time. If the
current preference fails twice, the next routing preference is tried.
LAR can be administered at an origination switch or a tandem switch. It can be
turned off at different points in the network to reduce network load. You use LAR
with AAR and ARS, GRS, and UDP) You can also use it with a FAC ISDN
Access Code. A LAR field is administered on the Route Pattern screen.
NOTE:
When LAR is used in a mixed network of Avaya MultiVantage Systems and
DEFINITY ECS switches, LAR ends at the DEFINITY ECS switch and
calls are rejected the normal way. However, if a LAR-triggering cause value
is passed back in the network to a DEFINITY server that is enabled for
LAR, LAR is attempted from that switch again.
Detailed description
LAR can be administered for each ISDN route preference in each Pattern Number.
The maximum number of LAR attempts per call per switch is 2 times the number
of route preferences in the route pattern. LAR can be administered at each
intermediate node that the call may be tandemed through to allow the attempt of
all possible routes.
You can control LAR by:
■ administering it on a per route-preference basis
■ partitioning trunks
■ limiting the number of hop counts