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

Topic Last Modified: 2010-07-14

In Microsoft Communications Server 2010, enhanced client registration, discovery, and routing improve service resiliency, and flexibility in design and deployment of your Enterprise Voice solution. A well-designed Enterprise Voice deployment can help meet your requirements for “always on dial tone.”

The Communications Server 2010 Registrar is a service that tracks clients, authenticates users, and provides routing services. The Registrar is not a standalone server role but is installed on Standard Edition servers, Front End Servers, and Survivable Branch Appliances.

Each user is assigned to a particular Registrar pool, which becomes that user’s primary Registrar pool. Each pool has a designated backup registrar pool which is used in failure scenarios.

Central Site Resiliency

In the case of data center failure, assuming a resilient WAN link between the two data centers, users whose primary Registrar pool is no longer available are automatically connected to the backup Registrar pool. A client does not need to know its primary or backup Registrar pool. The first logon server—typically a Director—will always direct the client to either the primary pool or, in the event of failover, to the backup pool.

If clients fail over to their backup Registrar pool, the following voice features will be available:

  • Outbound PSTN calls.

  • Inbound PSTN calls, if the carrier provides the ability to failover to a backup data center.

  • Enterprise calls both within a site and between sites.

  • Basic call handling, including call hold, retrieval, and transfer.

  • Advanced call handling, depending on user’s call-forwarding settings, including call forwarding, simultaneous ringing of endpoints, and call delegation features.

  • Call Detail Recording (CDR).

  • Location Information Service for emergency calls.

Branch Site Resiliency

For smaller branch sites without on-site IT administrators, a Survivable Branch Appliance (that is, a "branch in a box" that is easy to deploy, configure, and remotely manage) can provide basic voice services to users in the branch site during a WAN outage.

The Survivable Branch Appliance is a combination of a server (often a blade server) and a PSTN gateway, and runs in branch sites that do not have a Communications Server 2010 Enterprise pool or Standard Edition server. The Survivable Branch Appliance can provide basic phone services to users at the branch site when the WAN link to the Communications Server central site is down.

The blade server of the Survivable Branch Appliance runs the Windows Server 2008 operating system, and the Communications Server Registrar service and Mediation Server. Because the Survivable Branch Appliance runs at a remote site that may not have IT personnel, it is designed for easy deployment and remote management. Before a Survivable Branch Appliance is deployed, administrators can set up its account and configuration at the central site. A technician at the branch office then begins the deployment, and the rest of the deployment can be finished by the branch office technician, or done remotely by central site administrators, depending on the permissions given to the branch office technician.

In the event a branch office’s WAN connection to a data center fails, the Survivable Branch Appliance provides the following voice features to users in that branch office:

  • PSTN inbound and outbound calls

  • Intra-site and inter-site calls

  • Call hold, retrieve, and transfer

  • User authentication and authorization

  • Leaving and retrieving voicemail

  • Call forwarding, simultaneous ringing, boss-administrator, and team calling

  • Call Detail Recording (CDR).

  • All Two-party functionality, including instant messaging and audio-video conferencing

  • PSTN dial-in conferencing with Conferencing Auto-Attendant

See Also

Other Resources

Branch-Site Voice Resiliency