All the features discussed in this chapter are compelling reasons to use Lync Server 2013 as an organization’s UC solution, but users have come to expect a certain degree of reliability with communications, especially with a phone system. In Lync Server, all the features can be made redundant and resilient to a single server or site failures so that users can continue to operate in the event of a malfunction.
The methods of providing high-availability and disaster recovery for each server role vary and are outlined later, but steps have been taken to ensure that users can always hear a dial tone when they pick up a phone. Some key advancements include allowing a Mediation Server role to use multiple gateways, allowing inter-trunk routing that enables Lync to route between multiple PBXs, users receiving primary and backup pool information when signing in, and endpoints that don’t depend on Active Directory during a network failure. These types of changes have made Lync Server 2013 a highly reliable, end-to-end UC solution for an organization.