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

Topic Last Modified: 2010-07-18

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 IP/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, Communications Server 2010 Registrar, Mediation Server software, and an IP/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 an IP/PSTN gateway or a SIP trunk to a telephone service provider. A Survivable Branch Server is a Windows Server-based computer that has Communications Server 2010 Registrar and Mediation Server software installed on it.

For branch sites with more than 5,000 users and dedicated Communications Server administrators, we recommend a full Communications Server 2010 deployment, separate from that of the central site.

For guidance about choosing the best resiliency solution for the branch sites in your organization, as well as information about prerequisites and planning considerations, see Branch-Site Voice Resiliency, in the Planning Guide.

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