Most of the time, Lync Enterprise voice deployments need debate for collocated or stand-alone mediation server. Collocation of Mediation Server can reduce the TCO and data center footprints. Can Mediation server collocation be a wise option? To choose a wise option out of collocated or stand-alone mediation server depends on the following:
- Number of users enabled for UC-PSTN calls
- Number of UC-PSTN calls per user per hour
- Number of UC-PSTN calls at the time of peak load
- Connected gateway / SBC and mediation server
- Percentage of calls that support media bypass
- Branch sites configuration for UC-PSTN deployment
If I have missed any point here, please leave your comment so that I can add the same.
Any call which initiate from any Lync endpoint has two components signaling and media. For UC-PSTN calls, signaling always goes through Mediation server if stand-alone or Standard Edition / Front End server collocated with mediation server role.
No Media Bypass:
If your gateways, SBC or IP-PBX support media bypass, you can use collocated mediation server. But if you are planning for an option which do not support media bypass, I will advise you not to use collocated mediation server as collocated meditation server will increase load on front end servers which can cause of poor performance.
If you still want to use collocated meditation server, you can increase number of front end servers which can help you to distribute the load among front end servers.
A Stand-alone Mediation server deployment also depends on Branch sites which are connected to central site. If your branch sites don’t have dedicated PSTN connectivity then you should go with stand-alone mediation server pool. Again this topic requires more debate. As we know Lync 2013 use M:N trunk, in simple way it means if you have mediation server deployed in branch site and that can support media bypass you can still go with collocated option.
You can use Lync Planning tool to try all options and choose best out of that which provide you better ROI and best performance.