Migration of all Lync Server 2010 topologies and server roles is supported. You can migrate from one topology to a different topology, including from Standard Edition server to Enterprise Edition server.

Lync Server 2010 supports only the following migration method:

• Side-by-side migration. In side-by-side migration, Lync Server 2010 is deployed alongside an existing Office Communications Server 2007 or Office Communications Server 2007 R2 deployment, and then you transfer operations to the new servers and move users to Lync Server 2010. This method requires additional server platforms, including hardware and software, during migration, and system names and pool names are different in the new configuration. If it becomes necessary to roll back to the previous version, you can shift operations back to the previous servers.
  
  

Migration across Active Directory forests is not supported.

The recommended migration path is a phased approach. For details about migrating from a previous release, including the appropriate phasing of component deployment, see Migration from Office Communications Server 2007 R2 to Lync Server 2010 in the Migration documentation.

Lync Server 2010 can coexist with components of either an Office Communications Server 2007 deployment or an Office Communications Server 2007 R2 deployment. Concurrent deployment of Lync Server 2010 with both Office Communications Server 2007 and Office Communications Server 2007 R2 (concurrent deployment of all three versions) is not supported.

During a phased migration in which a previous Office Communications Server 2007 or Office Communications Server 2007 R2 deployment coexists temporarily with the new Lync Server 2010 deployment, support for mixed version routing is limited. For details, see the Migration documentation.

You can deploy a Lync Server 2010 database as new instance on an existing SQL Server on which you have deployed an Office Communications Server 2007 or Office Communications Server 2007 R2 database, if the hardware and software meet Lync Server 2010 requirements and minimum network requirements. You cannot use the same SQL instance for a Lync Server 2010 Front End pool that you use for an Office Communications Server 2007 or Office Communications Server 2007 R2 Front End pool.

Note:
If you intend to deploy server roles that are new to Lync Server 2010, such as a stand-alone A/V Conferencing Server or Survivable Branch Appliance, we recommend that you first upgrade your existing deployment as described in the Migration documentation and the Deployment documentation, and then deploy the new server roles as described in the Planning documentation and Deployment documentation.

For specific coexistence requirements and other details about coexistence and migration of Office Communications Server 2007 or Office Communications Server 2007 R2 and Lync Server 2010 components, see Migration from Office Communications Server 2007 R2 to Lync Server 2010 and Migration from Office Communications Server 2007 to Lync Server 2010 in the Migration documentation. For details about coexistence of Lync Server 2010 pools and Directors with Office Communications Server 2007 or Office Communications Server 2007 R2 pools and Directors, see Coexistence Changes in the Planning documentation. For details about mixed version support for clients, see Supported Clients from Previous Deployments. For details about support for previous UCMA applications, see Migrate Applications Built on Microsoft Unified Communications Managed API (UCMA) 2.0 Core SDK in the Planning documentation.