The Mediation Server service has encountered a major connectivity problem with these Trunk peer(s). Affected PSTN Trunk Service ...

Lync Server 2013

The Mediation Server service has encountered a major connectivity problem with these Trunk peer(s).

Affected PSTN Trunk Service Cluster(s): 
%1
Cause: MEDIATIONSERVER_GATEWAY_OPTIONS_FAILED (Event ID: 25051) was recorded 5 times.  Check other MOM alerts for more details. The MEDIATIONSERVER_GATEWAY_IP_NOT_AVAILABLE (Event ID: 25036), MEDIATIONSERVER_GATEWAY_TLS_NEGOTIATION_FAILED (Event ID: 25040) are examples of events that signal connectivity error conditions with the Trunk peer.
Resolution:
If the failure is MEDIATIONSERVER_GATEWAY_IP_NOT_AVAILABLE (Event ID: 25036), make sure that the correct listening IP and port for the Trunk have been configured in the PSTN Trunk object in management store and that the Trunk is up and running and able to accept incoming connections from the Mediation Server.  If the failure is MEDIATIONSERVER_GATEWAY_TLS_NEGOTIATION_FAILED (Event ID: 25040), make sure that both the Mediation Server and the Trunk are configured for TLS and that the CA for the Trunk's certificate is the trusted certificate path on the Mediation Server and the CA for the Mediation Server's certificate is in the trusted certificate path on the Trunk.

The Mediation Server service failed a call because of too little bandwidth available on the Trunk leg of a call. The Mediation ... The Mediation Server service has encountered a major call completion problem with the Front End. Front End FQDN: %1 Cause: ... The Mediation Server service has encountered a major call completion problem with these Trunk peer(s). Affected PSTN Trunk ... The Mediation Server service has encountered a major connectivity problem with the Front End. Front End FQDN: %1 Cause: ... The Mediation Server service has encountered a major connectivity problem with these Trunk peer(s). Affected PSTN Trunk Service ... The Mediation Server service has encountered a major internal problem that may be causing it to fail calls. Cause: Check ... The Mediation Server service has encountered a major MRAS connection problem with the Front End. Cause: The MEDIATIONSER ... The Mediation Server service has encountered a major problem with its configurations. Cause: Check the following MOM alerts ... The Mediation Server service has received a call that does not support comfort noise. This event is throttled after 5 calls ...