Nortel Networks SRG 50 NN43001-307 User Manual

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Alternative Call Routing for Network Bandwidth Management

How Alternative Call Routing for NBWM works

When a user dials a station-to-station call between two different zones (that
is, the calling and called telephones are not located in the same geographic
area) and the bandwidth limit has been reached, then the Alternative Call
Routing feature is invoked.

The following steps occur in Alternative Call Routing scenarios.

Call from branch office telephone in Normal Mode

1. The interzone station-to-station call is attempted. There is insufficient

bandwidth available to make the call.

2. The main office inserts the ALTPrefix associated with the originator’s

zone (the branch office in this case) before the dialed digits.

3. The main office uses Coordinated Dialing Plan (CDP) or Vacant Number

Routing (VNR) to route the call to a virtual trunk.

4. A request is made to the NRS in order to determine the endpoint. The

NRS returns the branch office address as the endpoint.

5. The call is routed on the virtual trunk to the branch office.

6. The branch office treats the ALTPrefix as a steering code. The

branch office determines the Route List Index (RLI) and uses a
Digit Manipulation Index (DMI) to change the dialed number into a
PSTN/MCDN format number.

7. The call is routed over the PSTN/MCDN trunks to the telephone at the

main office or other branch office.

Call from main office telephone to branch office telephone

1. The interzone station-to-station call is attempted. There is insufficient

bandwidth available to make the call.

2. The main office inserts the ALTPrefix associated with the originator’s

zone (the main office in this case) before the dialed digits.

3. The main office uses CDP and recognizes the ALTPrefix as a steering

code.

4. The main office determines the RLI and uses a DMI to change the

dialed number into a PSTN/MCDN format number.

5. The call is routed over the PSTN/MCDN to the telephone at the branch

office.

With the ALTPrefix digits inserted, the resulting number must be one that
CDP or VNR software can process as a steering code.

Nortel Communication Server 1000

Main Office Configuration Guide for SRG 50

NN43001-307

02.02

Standard

Release 5.0

3 December 2007