Topic Last Modified: 2010-10-07

In Microsoft Lync Server 2010, you define sites that contain Lync Server 2010 components. A site in Lync Server is a set of Lync Server computers that are well connected by a high-speed, low-latency network, such as a single local area network (LAN) or two LANs connected by a high-speed fiber optic network.

Although the use of sites in Lync Server and Active Directory Domain Services are similar, your Lync Server sites can be different from your Active Directory Domain Services and Microsoft Exchange Server sites. Lync Server does not use the sites you have defined for Active Directory Domain Services.

A Lync Server site can be either a central site or a branch site. A central site contains at least one Front End pool or one Standard Edition server. A branch site is associated with exactly one central site, and the users at the branch site get most of their Lync Server functionality from the servers at the associated central site.Each branch site contains at least a public switched telephone network (PSTN) connection and can also include a Mediation Server. Alternatively, a branch site could run a Survivable Branch Appliance, which is a new device introduced in Lync Server 2010 that combines a PSTN gateway with a Lync Server Registrar and Mediation Server.

Branch sites with a Survivable Branch Appliance can retain Enterprise Voice communications if the WAN fails or the central site goes offline. For details about the Survivable Branch Appliance and branch site resiliency, see Planning for Enterprise Voice Resiliency in the Planning documentation.