There are many features that I just love when it comes to Lync Server 2010 and Lync 2010 clients. One of my favorite new features is the support of multiple SRV records.
In Office Communications Server 2007 and 2007 R2, you can configure an Service Location (SRV) record for remote users so that they can use the automatic configuration setting in the client to find the Edge server environment and sign-in. However, OCS 2007 and 2007 R2 are not able to handle multiple SRV records. So, if you have multi-site environment, all users would come in via a single Edge server environment even if you had two Edge servers like in the Visio diagram.
In this drawing, only one Edge environment is accessible via automatic configuration settings. So, let’s say that that Denver is the preferred Edge environment for remote users. Of course, any users in London will have to go through Denver and then route through the WAN link to get to their home pool.
The problem with this being OCS 2007 and the Office Communicator client for remote users is that in the event of a failure of the Denver Edge environment, we would have to go into DNS and reconfigure the SRV record to point to the London Edge environment. We would have no access for remote users until their DNS cache expires and the DNS change has propagated through the Internet.
In Lync, with Lync servers and Lync clients, we can create two SRV records. One each for the Denver and London Edge environments. We can adjust the priority and weight settings for the records to modify the behavior of clients. Also, in the event of a failure of one Edge environment, the other will still be accessible and will be able to be used by the remote users running the Lync client.
Of course, this will require a Host (A) record for each Edge environment and a Service Location (SRV) record for each Edge environment.