Cisco Call manager 5.x & 6.x

The Microsoft document That explains how to set up the call manager systems is missing one part if you want to have the traffic come through on TCP rather than UDP for Unified Communications. This is important to remember to change this setting in the call manager system. during the setup of the new Sip trunk other wise there will be a situation like the following

If you call into an Auto attendant or Subscriber access the UM role on that is a part of exchange will not pick up it will either just ring or it will ring and answer to "Dead Air"

To fix this problem you will have to set the Traffic To TCP rather then the Default UDP.