Nortel Networks NN43001-314 User Manual

Page 142

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142

Alternative Call Routing for Network Bandwidth Management

2. The main office Call Server determines there is insufficient bandwidth

between the BO2 and BO1 zones.

3. The Call Server inserts the ALTPrefix configured for the BO2 zone prior

to IP Phone F’s telephone number, dialed by the user.

Example: ALTPrefix assigned is 222.The dialed number becomes 222
6020.

4. The call is routed to the virtual trunk by CDP or VNR. The virtual trunk

sends a request to the NRS for address resolution. The digit string sent
to the NRS contains the ALTPrefix. The NRS returns the IP address of
the Branch Office endpoint to the virtual trunk.

5. The virtual trunk places the call to the Branch Office.

The Branch Office receives the call and recognizes the first part of the
number as a Steering Code. The call is steered to an RLI. The DMI
manipulates the number into a PSTN number and the Branch Office
outpulses the digits to the Central Office (CO) serving the Branch Office.
(This may be the same CO as the one serving the main office.) If the
alternate route has MCDN trunks in the BO2 zone, the call is outpulsed
on one of these trunks, after the Branch Office uses Digit Manipulation
(action labeled 2 in

Figure 53 "Example of an alternately routed call

between a Branch Office telephone and another Branch Office te" (page
139)

Example: The digit string 2226 is programmed as a Distant Steering
Code (DSC) at the Branch Office. Calls starting with this DSC are
handled by an RLI with PSTN trunks as an entry. If the Public format
number for the destination telephone is a DID number, then the Digit
Manipulation Index associated with the PSTN route must:

•

delete 3 digits (remove the ALTPrefix 222)

•

insert 1506348 (to compose the DID number of the destination
telephone, which is 15063486020)

6. The call comes into IP Phone F from the PSTN in the BO1 zone (action

labeled 3 in

Figure 53 "Example of an alternately routed call between a

Branch Office telephone and another Branch Office te" (page 139)

Alternative Call Routing for NBWM feature used in All Calls mode

The situations illustrated in

Figure 49 "Example of an alternately routed call

between a Branch Office telephone in Normal Mode and a main of" (page
132)