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.
You can configure translation patterns to manipulate digits for any type of call. Translation patterns follow the same general rules and use the same wildcards as route patterns. As with route patterns, you assign a translation pattern to a partition. However, when the dialed digits match the translation pattern, Unified CM does not route the call to an outside entity such as a gateway; instead, it performs the translation first and then routes the call again, this time using the calling search space that is configured within the translation pattern.
For each translation pattern that you create, ensure that the combination of partition, route filter, and numbering plan is unique. If you receive an error that indicates duplicate entries, check the route pattern or hunt pilot, translation pattern, directory number, call park number, call pickup number, or meet-me number configuration windows.
Transformation patterns can be used to discard digits, add prefix digits, add a calling party transformation mask, and control the presentation of the calling party number before the system sends the call to the phone or to the PSTN.
Configure transformation patterns and associate them to a route partition, thereby assigning the pattern to the calling search space that contains the partition. You can assign the pattern to the call settings for a specific device, device pool, gateway, or trunk via the Calling Party Transformation CSS or Called Party Transformation CSS fields in the configuration windows.
You can configure the following transformation patterns:
Calling Party Transformation Patterns — Allow the system to adapt the global form of the calling party's number into the local form required by off-cluster networks connected to the route group devices, such as gateways or trunks.
Called Party Transformation Patterns — Allow the system to adapt the global form of the called party's number into the local form required by off-cluster networks connected to the route group devices.
The system has a three-tiered approach to route planning that uses the following components:
Route Patterns — The system searches for a configured route pattern that matches the external dial string and uses it to direct the call to a gateway or route list. You can assign route patterns to gateways, trunks, or to a route list that includes one or more route groups.
Route Lists — A prioritized list of the available paths for the call.
Route Groups — The available paths; the route group distributes the call to gateways and trunks.
Additional Call Routing
The route plan can also include the following optional components:
Local Route Groups — If you have multiple sites, you can use local route groups so that Off-Net calls can be routed to a gateway as specified by the device pool rather than by the route pattern configuration. This allows you to use a single set of route patterns for multiple locations.
Route Filters — Create route filters and add them to your route patterns or hunt pilots to restrict users from using the pattern. Route filters are mandatory is you are using a dial plan installer file, but are optional for manual dial plan configurations. For manual configurations, route filters apply only if your pattern uses the @ wildcard.
Automated Alternate Routing — Automatically reroute calls through the PSTN or another network when the system blocks a call due to insufficient bandwidth.
Time-of-day Routing — Create a time schedule that specifies when a given partition is available to receive incoming calls.