Trunks

The term trunk is often overused, and its meaning has slightly changed in Lync Server 2013 now that a single gateway can be associated to multiple Mediation pools. In Lync Server 2013 a trunk consists of an IP/PSTN gateway name or IP, a listening port on the IP/PSTN gateway, a Mediation Server, and a listening port on the Mediation Server. Routes now include a list of trunks, instead of gateways, which can be used to place a call after a route is selected. Figure 32.3 shows how a single media gateway or IP PBX can now be associated with multiple Mediation pools using the new M:N trunk feature.

Figure 32.3. M:N trunk associations.

In a scenario with a single Mediation Server and gateway, not much has changed. The advantages are seen when multiple Mediation pools exist because each can be paired with the same gateway for redundancy. If one trunk is unavailable because a Mediation pool is offline, the other trunk and Mediation pool can connect to the same gateway. From an inbound perspective, the gateway can deliver calls to either Mediation pool in a round-robin or a primary/secondary configuration done on the gateway itself.

In Lync Server 2010 this same concept was possible, but because it required some DNS tricks with virtual PSTN gateway objects, it was a bit messier.