In nearly every deployment, you should use the side-by-side migration path. In a side-by-side migration, you deploy a new server with Office Communications Server 2007 R2 alongside a corresponding server that is running Office Communications Server 2007, and then you transfer operations to the new server. This path is faster and easier than remove/reinstall migration, which is described later in this section, and it imposes very little downtime on your users. If it becomes necessary to roll back to Office Communications Server 2007, you have only to shift operations back to the original servers.

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