PSTN Reroute

Another feature within the voice policy that requires some additional planning is the PSTN Reroute check box. The idea of this feature is that if the WAN connection between two users is unavailable or constrained by Call Admission Control, the call is placed through the PSTN, even if toll charges are incurred. The configuration step that administrators often miss is that the user’s voice policy still controls what numbers can be called. So if a user has a voice policy that does not allow national or international dialing, a PSTN reroute to a number matching those patterns might fail.

The best practice here is to create PSTN usages and routes that match patterns for the organization’s own DIDs. This usage can then be inserted in voice policies to allow PSTN reroute to occur, independently of allowing national or international calls to other numbers.

When beginning to plan voice policies, use the following tips:

• Review the various features in voice policies and determine which ones will be allowed.

• Determine how many different voice policies, or classes of service, are required for each site.

• Decide whether tail-end hop off will be implemented in the voice policies.

• Consider the trunk capacity if allowing the simultaneous ring feature in voice policies.

• Create PSTN usages and routes for internal numbers for PSTN reroute purposes.