Topic Last Modified: 2011-03-15

The reference topology with high availability and a single data center is designed for a small-to-medium size organization with one central site. The exact topology in the following diagram is for an organization of 15,000 users. Typically, the type of topology shown in the following diagram is recommended for organizations with 5,000 to 30,000 users, but it can support over 30,000 users.

MORG Reference Topology
  • Active Directory deployment.   All Microsoft Lync Server 2010 communications software deployments reside in a single Active Directory forest. For this topology, the customer has Lync Server deployed in the child domain,

  • Accommodate more users by adding more Front End Servers.   The exact topology in this diagram has three Front End Servers, so it supports up to 20,000 users. If you have a single central site and more users, you can simply add Front End Servers to the pool. The maximum number of users per pool is 80,000, with eight Front End Servers.

    However, the single site topology can support even more users by adding another Front End pool to the site. To support these extra users, you need to add only one additional Front End pool (that is, just one pool each of A/V Conferencing Servers, Edge Servers, and Directors are sufficient, although more servers may need to be added to these pools).

  • A/V Conferencing service can be collocated in smaller organizations.   If this organization has 10,000 or fewer users, you could decide to collocate the A/V Conferencing service with the Front End pool, instead of deploying a separate A/V Conferencing pool. For organizations with 10,000 or more users, collocating these services is not recommended for performance reasons.

  • Monitoring Server database options.   In this topology, the Monitoring Server is using the same pair of database servers that the Front End pool uses. A topology in which the Monitoring Server has its own database servers is also supported.

  • High availability for all server pools.   In this example organization with 15,000 users, just one Director server, Edge Server and A/V Conferencing Server would be sufficient for performance. However, there are pools of two servers of each type deployed to provide high availability for each feature.

  • Branch site deployment options.   The organization in this topology has Enterprise Voice deployed as their voice solution. Branch Site 1 does not have a resilient wide area network (WAN) link to the central site, so it has a Survivable Branch Appliance deployed to maintain many Lync Server features in case the WAN link to the central site goes down. Branch Site 2 however has a resilient WAN link, so only a public switched telephone network (PSTN) gateway is needed. The PSTN gateway deployed there supports media bypass, so no Mediation Server is needed at Branch Site 2. For details about deciding what to deploy at a branch site, see Planning for Branch-Site Voice Resiliency in the Planning documentation.

  • DNS load balancing.   The Front End pool, Edge Server pool, and the Director pool have DNS load balancing for SIP traffic deployed. This eliminates the need for hardware load balancers for the Edge Servers, and significantly lessens the setup and maintenance of the hardware load balancers for the other pools, as the hardware load balancers are needed only for HTTP traffic. For details about DNS load balancing, see DNS Load Balancing in the Planning documentation.

  • Exchange UM deployment. This reference topology includes an Exchange Unified Messaging (UM) Server, which runs Microsoft Exchange Server, not Lync Server. The Exchange UM routing functionality for Lync Server runs on the Front End pool.

    For details about Exchange UM, see On-Premises Exchange Unified Messaging Integration and Hosted Exchange Unified Messaging Integration in the Planning documentation.

  • Edge Servers are recommended.   Although deploying an Edge Server is not required, we recommend it for any size of deployment. 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! Note that 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 high availability and a single data center