Nortel Meridian Meridian 1 Feature Description And Administration page 924

Page 924 of 1814
553-2901-301 Standard 9.00 January 2002
ISDN QSIG Alternate Routing
This feature uses the routing capability of Network Alternate Route Selection
(NARS) to re-route a congested call. For each QSIG call translated at a
Meridian 1 node, NARS selects one route from up to 512 routes to complete
the call. These routes are programmed in a route list. Each route in the list is
called an entry. There may be up to 64 entries in each route list. Any
combination of trunks (such as public exchange, TIE) can be specified in a
route list.
QSIG Alternate Routing may be configured for each of the 512 different
routes.
Congestion occurs when all trunks of a route are busy. With the introduction
of the QSIG Alternate Routing feature, each entry of a route list on one node
can be configured to take an alternate entry (route) from the route list of that
node (Private or Public Exchange), if congestion is encountered.
Using LD 86, the Electronic Switched Network (ESN) administration
overlay, the option defined for the Step Back On Congestion (SBOC) prompt
determines the type of alternate routing available to calls over a particular
route. These options may be as follows:
• NRR (no alternate routing is performed. The call receives congestion
treatment).
• RRO (reroute if a call encounters congestion at the originating node. If
congestion is encountered at a transit node, the call drops back to the
originating node, so that the originating node decides if re-routing is
required. The drop-back functionality, which is part of the ISDN Drop
Back Busy feature, is also configured in LD 86, using the IDBB prompt).
• RRA (reroute the call at any node, whether congestion is encountered at
the originating or transit node).
QSIG Alternate Routing is triggered at the controlling node when a Call
Clearing message (DISCONNECT or a REJECT) is received, and the cause
value is to activate QSIG Alternate Routing. The cause values are defined
using LD 86 (see page 932).