[This is pre-release documentation and subject to change in future releases. This topic's current status is: Milestone-Ready]

Topic Last Modified: 2010-07-13

In Microsoft Communications Server 2010, on your network you define sites that contain Communications Server 2010 components. A site represents a geographical location of your network, and is a set of computers well-connected by a high-speed, low-latency network, such as a single local area network (LAN) or two networks connected by a high-speed fiber optic network. Note that Communications Server sites are a separate concept from Active Directory sites and Microsoft Exchange sites.

Site Types

Each site is either a central site, which contains at least one Front End pool or Standard Edition Server, or a branch site. Each branch site is associated with exactly one central site, and the users at the branch site get most of their Communications Server functionality from the servers at the associated central site.

Each branch site contains one of the following:

  • A survivable branch appliance, which is a new device introduced in Communications Server 2010 that combines a PSTN gateway with some Communications Server functionality.

  • A public switched telephone network (PSTN) gateway and, optionally, a Mediation Server.

A branch office with a resilient WAN link to a central site can use the second option, a PSTN gateway and optionally a Mediation Server. Branch office sites with less-resilient links should use a survivable branch appliance, which provide resiliency in times of wide-area network failures. For example, in a site with a survivable branch appliance deployed, users can still make and receive Enterprise Voice calls if the WAN connecting the branch site to the central site is down. For details about the survivable branch appliance and this resiliency, see Branch-Site Voice Resiliency.

Site Topologies

Your deployment must include at least one central site, and can include zero to many branch sites. Each branch site is affiliated with one central site. The central site provides the Communications Server services to the branch site that are not located locally at the branch site.