Topic Last Modified: 2011-03-15

The reference topology with limited high availability is for an organization that wants to deploy Microsoft Lync Server 2010 communications software functionality at a minimum cost. Typically, the specific topology shown in the following diagram is recommended for organizations with 5,000 or fewer users, although you can support additional users by adding additional Standard Edition servers.

SORG Topology diagram
  • Active Directory deployment.   All Lync Server deployments reside in a single Active Directory forest. For this topology, the customer has Lync Server deployed in the child domain,

  • Voice pilot.   The organization using the exact topology shown in this diagram is currently running a pilot program of the Enterprise Voice feature of Lync Server. Some users are using Lync Server as their sole voice solution.

    If they go on to fully deploy Enterprise Voice and remove the PBX system, they should provide high availability for their voice solution by deploying a second Standard Edition server or moving to a Front End pool. A single Standard Edition topology as shown in this diagram is recommended only if you are not deploying Enterprise Voice in a production environment. Because being able to make calls is mission critical for almost every organization, you should provide high availability if you use Enterprise Voice as your telephone solution.

  • Another Standard Edition server can be added.   A single Standard Edition server can support up to 5,000 users. If you want to accommodate more users or provide some high availability capability for Enterprise Voice (at a minimum cost), you could add another Standard Edition server to this topology.

    For a true high availability solution, you should deploy Enterprise Edition and deploy a Front End pool. Although having two Standard Edition servers would maintain Enterprise Voice functionality should one of these servers go down, a Front End pool provides much better continuity of service for other Lync Server features.

  • Branch site survivability.   This organization is running the Enterprise Voice pilot with some branch site users as well. The branch office does not have a reliable wide area network (WAN) link to the central site, so a Survivable Branch Appliance is deployed there. With this deployed, if the WAN link goes down users at the branch site can still make and receive calls (both calls within the organization and PSTN calls), have voice mail functionality, communicate with two-party instant messaging (IM). Users can also be authenticated when the WAN link is unavailable as well.

  • Edge Server deployment is recommended.   Although deploying an Edge Server is not required for internal IM, presence and conferencing, we recommend it even for small deployments. You can maximize your Lync Server investment by deploying an Edge Server to provide service to users currently outside your organization’s firewalls. The benefits include the following:

    • Your organization’s own users can use Lync Server functionality, if they are working from home or are out on the road.

    • Your users can invite outside users to participate in meetings.

    • If you have a partner, vendor or customer organization that also uses Lync Server, you can form a federated relationship with that organization. Your Lync Server deployment would then recognize users from that federated organization, leading to better collaboration.

    • Your users can exchange instant messages with users of public IM services, including any or all of the following: Windows Live, AOL, and Yahoo! A separate license might be required for public IM connectivity with Windows Live, AOL, and Yahoo!

    • If you also deploy the Lync Server XMPP Gateway, you can enable your users to exchange instant messages with the users of providers and servers that use Extensible Messaging and Presence Protocol (XMPP), such as Google Talk and Jabber.

      To use XMPP, you must install the XMPP Gateway. You can download the XMPP Gateway from the Microsoft Download Center at After you install the XMPP Gateway, you need to install the hotfix, which is available for download from

    Reference topology with limited high availability