User's Manual

Appendix E: Branch PSTN call routing
examples
Each B5800 Branch Gateway system can support its own external PSTN trunks. When deployed in an
Avaya Aura
®
network, you have considerable flexibility over where outgoing PSTN calls should emerge
from the network and similarly where incoming calls should be routed.
The following examples demonstrate some of the options available:
•
Centralized call control on page 325 — External calls at a branch site can be rerouted to be dialed
out at another site. This can be done for reasons of call cost and call control. For example, the central
site may have a bulk call tariff for national and international calls that would benefit all branches.
•
Branch PSTN Override on page 328 — Having configured the branch to send outgoing external
calls to the Avaya Aura
®
Session Manager for onward routing, there may be cases where a specific
number should still be routed via the branches own PSTN trunks.
•
PSTN Fallback on page 330 — The B5800 Branch Gateway can be configured to allow some calls
that would normally use the Avaya Aura
®
Session Manager line to be routed via the PSTN when the
Avaya Aura
®
Session Manager line is not available.
The various methods used in these examples can be combined to match the customer's needs. However
the main aim should be as follows:
• To keep the branch configuration as generic as possible, i.e. to use the same PSTN call control in
all branch configurations. This simplifies maintenance of multiple branches.
• To centralize as much of the PSTN call control in the Avaya Aura
®
Session Manager as possible.
Again this simplifies maintenance and control.
Centralized call control
External calls at a branch site can be rerouted to be dialed out at another site, typically the
headquarters site. This can be done for reasons of call cost and control and to reduce the
external PSTN capacity required at the individual branch sites.
In this example we route all national and international calls to the headquarters site. The Avaya
Aura
®
Session Manager there routes the calls out via PSTN services at that site. Note,
however, that the Avaya Aura
®
Session Manager could alternately use the trunks at a branch
for some calls. For example, if the national call is to an area code that is local to a particular
branch, the call could be routed to that branch for dialing on its PSTN trunks.
Implementing the Avaya B5800 Branch Gateway November 2011 325