Topic Last Modified: 2012-10-10

Resilient Enterprise Voice refers to branch-site resiliency, that is, the ability to provide continuous Enterprise Voice service to branch site users in the event that the link to the central site becomes unavailable.

For small and medium-sized branch sites (branch sites with 25 to 1,000 users), we recommend deploying a Survivable Branch Appliance, which will terminate public switched telephone network (PSTN) calls by using its built-in PSTN gateway or a SIP trunk to a telephone service provider. A Survivable Branch Appliance is a third-party device that includes a blade server running the Windows Server 2008 R2 operating system, Lync Server 2013 Registrar, Mediation Server software, and a PSTN gateway, all in a single appliance chassis.

For branch sites with 1,000 to 5,000 users and no resilient WAN, we recommend a Survivable Branch Server connected to either a PSTN gateway or a SIP trunk to a telephone service provider. A Survivable Branch Server is a Windows Server-based computer that has Registrar and Mediation Server software installed on it.

Note:
For branch sites with more than 5,000 users and dedicated Lync Server administrators, we recommend a full Lync Server 2013 deployment, separate from that of the central site.

For details about choosing the best resiliency solution for the branch sites in your organization, including prerequisites and planning considerations, see Branch-site resiliency requirements in the Planning documentation.

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