I joined the Lync Dedicated team in Office 365 4 years ago to help launch our voice offering in the cloud.
The offering allows for PSTN connectivity using Sip Trunks from qualified UCOIP vendors who connect to our approved Edge Sites or the customer can deploy their own SBC, also from the UCOIP qualified devices.
In that time our customers have upgraded from Lync 2010 to Lync 2013 pools but we kept the Mediation Servers running at Lync 2010 versions. The time to upgrade them is now upon us and while I'd hope for a rinse repeat process, we are dealing with individual corporations and their production voice infrastructure.
Here are just some of the approaches we are taking
One customer is adding an SBC to an existing configuration with SIP Trunk vendor. The approach here is to create a new voice site with a new number range that will be assigned to test users. The dial plan details will include only the SBC as the outbound path for PSTN allowing us to test the infrastructure components without disrupting the SIP Trunk traffic using the 2010 Mediation Servers. When this test topology is fully tested and signed off, the plan is to modify the production dial plans to now use the SBC as the outbound path instead of the SIP Trunk vendor.
Another customer has 2 SIP Trunk vendors, one for the US and another for Canada. The contracts with each carrier are owned by the customer and ultimately they must approve of the change as well as provide us the approved day/time to do the work without disrupting the production service. The approach for this will be to work with each carrier independently and modify the topology to use the new Lync 2013 Mediation Servers instead of the 2010 servers. The nice thing about this approach is that both carriers can be done independent and service will function with a mix of Lync 2010 and 2013 Mediation Servers in use. The approach would be a hot cut in the change window and test the call flow. In the event a problem is identified, you can simply roll the change back to the 2010 servers.
These little differences are what offer the jolt to my day and not become stuck in a routine.