Call Routing Overview
The system uses route plans to determine how to route calls between clusters, and how to route external calls to a private network or to the Public Switched Telephone Network (PSTN). The route plan that you configure specifies the path that the system uses to route each type of call. For example, you can create a route plan that uses the IP network for on-net calls, or that uses one carrier for local PSTN calls and another for international calls.
The system has a three-tiered approach to route planning that uses the following components:
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Route Patterns—The system searches for a configured route pattern that matches the external dialed string and uses it to select a gateway or a corresponding route list.
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Route Lists—A prioritized list of the available paths for the call.
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Route Groups—The available paths; the route group distributes the call to gateways and trunks.
In addition to these building blocks, the route plan can also include the following components:
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Local Route Groups—Decouple the location of a PSTN gateway from the route patterns that are used to access the gateway.
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Route Filters—Restrict certain numbers that are otherwise allowed by the route pattern.
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Automated Alternate Routing—Automatically reroute calls through the PSTN or other network when the system blocks a call due to insufficient bandwidth.
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Time-of-day Routing—Create a time schedule that specifies when a partition is available to receive incoming calls.