Routes
,Routes in Lync Server 2010 are a definition of where to send calls that match a specific dial string. Administrators define a matching pattern and a gateway or gateways associated with the pattern to send a call. Each route is also associated with PSTN usages to define what type of call this might be.
The PSTN usage defined varies depending on the gateway associated with the route. For example, a route matching the +1312 area code associated with an IP/PSTN gateway in Chicago might be considered a PSTN usage of Local, but when associated with an IP/PSTN gateway in San Francisco, it necessitates a PSTN usage of Long Distance.
Route Resilience
Resiliency for routes is done by providing multiple gateways in a single route, or by creating a redundant route that uses a gateway in a different location. Routes are processed in from a top-to-bottom order so that the priority for a route can specified by adjusting the route placement within the list. For example, a route matching the +1312 area code using an IP/PSTN gateway in Chicago should be placed higher in the list than a route matching the same string using an IP/PSTN gateway in San Francisco because it is considered a local call to the Chicago gateways.
There are two aspects to consider when planning for route resilience in Lync Server 2010: high availability in the primary site and resilience in a failover scenario. High availability is typically achieved by associating multiple gateways within the same location with the route and PSTN usage. In this example, Lync Server 2010 round-robins requests across the two IP/PSTN gateways in Chicago when operating at full capacity. If one of the gateways fails, calls are sent only to the gateway still available.
If both of these gateways fail, an organization might want to still route calls to the destination number, but accept potential long distance charges and route calls out at the gateway in another physical site. This is accomplished by creating a second route with the same dial string, different gateway, and different PSTN usage.
Caution
This additional, backup PSTN usage associated with the backup route should be associated only with voice policies allowed to use this secondary route. For user accounts with a voice policy not including this usage, the calls would fail when both primary IP/PSTN gateways are unavailable.
Continuing the example, assume Company ABC also has an IP/PSTN gateway in San Francisco and a secondary route for the +1312 area code using this gateway. The primary route for +1312 should use the Chicago IP/PSTN gateway. Additionally, a PSTN usage of Chicago Backup Long Distance is associated with the secondary route. A voice policy including the Local and Chicago Backup Long Distance PSTN usages is created and assigned to San Francisco users. This ensures that in the event of both Chicago IP/PSTN gateways becoming unavailable, calls are routed out the San Francisco IP/PSTN gateway. This scenario is shown in Figure 28.1. The reason the San Francisco gateway is not associated with the same route as the Chicago gateways is that Lync Server will distribute outbound calls to each gateway equally. To use San Francisco only as a backup route, it needs to have a unique route and PSTN usage associated.
Figure 28.1 Route Resilience Example
