Topic Last Modified: 2012-09-21
Branch site users get most of their Lync Server 2013 functionality from the server at the central site that the branch site is associated with. Each branch site is associated with exactly one central site. To provide calls to and from the public switched telephone network (PSTN), a branch site might contain any of the following:
A PSTN gateway and possibly a Meditation Server
A SIP trunk
An existing voice infrastructure with a private branch exchange (PBX)
A Survivable Branch Appliance
A Survivable Branch Server
Branch sites with a Survivable Branch Appliance or a Survivable Branch Server are more resilient in times of wide-area network or central site failures than branch sites without one of these solutions. For example, in a site with a Survivable Branch Appliance or a Survivable Branch Server deployed, users can still make and receive PSTN calls if the network connecting the branch site to the central site is down. Another way to achieve branch-site resiliency is by using a PSTN gateway or a SIP trunk with a full-scale Lync Server deployment at the branch site.
For details about which branch site deployment is right for your organization, including prerequisites and other planning considerations, see Planning for PSTN Connectivity and Planning for branch-site voice resiliency in the Planning documentation.