Survivable Branch Office Telephony – the easy way!

Support for resilient telephony in branch offices during WAN outages is not a new feature – some vendors offer it for several years already. Microsoft’s new Lync based solution sets a new benchmark: no specialists are needed for deployment and it can be done in far less than an hour! Unbelievable? Let’s see…

Step 1: Preparation in Data Center

A few administrative settings have to be done before a Survivable Branch Appliance (SBA) can be installed:

  • Create SBA computer account and delegate domain join to RTCUniversalSBATechnicians group. Set the service principal name to HOST/sba-fqdn
  • Add user account of branch office technician to RTCUniversalSBATechnicians group.
  • Add SBA to branch office site using wizard in topology builder and publish topology.
  • Optional: Allow RTCUniversalSBATechnicians group to use WebServer template in Enterprise CA.

Step 2: SBA deployment in branch office

All qualified SBA products include a web based user interface pre-installed by the manufacturer. It supports deployment without the need to connect a keyboard and a monitor due to the nature of an appliance. Microsoft requires a minimum set of functions supported by this web UI – it’s up to the vendor to include optional features. I will use screenshots of our OfficeMaster SBA as an example here. At the end of this article you will find a link to a video demonstrating the full deployment process using this Silverlight-based UI.       Bootstrap steps consist of:

  • Network configuration
  • Changing preinstalled local administrator password
  • Setting time zone, date and time
  • Joining SBA machine to domain (and automatically adding RTCUniversalSBATechnicians group to local administrators).


After rebooting the machine and clicking “Done” the “Install” section is opened.  In this part all modules required to run the SBA are deployed:

  • SQL Express 2008
  • Lync Server core components
  • Lync Server (Registrar)
  • Mediation Server


Subsequently another reboot is required. After logging in using the branch office technician account the “Activate” section is shown. The steps in this part include:

  • “Find Central Management Store” – This is not mandatory but it helps to ensure that CMS can be accessed, which is necessary for downloading the configuration.
  • Download and install configuration to SBA – these steps avoid the necessity to wait for replication.
  • Starting replica process.
  • Activation of SBA.


Second part of activation (which is not shown here as a screenshot) consists of:

  • Requesting and installing a certificate, which is needed for (M)TLS. The easiest way is using online access to an Enterprise Certificate Authority. If that is not supported, the certificate signing request can be created and submitted to any certificate authority.
  • The certificate must be assigned to Lync services.
  • Finally all services are started – this completes SBA deployment; the only step left is the configuration of the integrated media gateway.

In OfficeMaster SBA the complete media gateway is contained on a full size PCIe card. The gateway is recognized by the host machine as another network interface. It typically gets assigned a static IP address, which is also resolved by DNS. In addition the type and number of ISDN interfaces must be configured:


Finally a basic dial plan for the gateway should be configured:


In this example extension length zero was used because the BRI port is connected to an ISDN interface using multiple subscriber numbers (MSNs) instead of extension digits. Clicking the “Browse” button supports assigning pre-configured analog phone numbers to gateway ports. This helps to avoid mistyping when entering that information manually. At this point the deployment is completed! Some optional steps supported by the UI are:

  • Placing an outbound PSTN test call
  • Testing inbound calls
  • Backup and restore of gateway configuration

During normal operation the web UI also provides diagnostic functions to show event log entries and to display PSTN interface status, state of replication and other useful information. Details on this and a complete walkthrough is shown in this video (100MB, 7 minutes).

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