Consider the following scenario:
You develop an auto-provisioning application by using Microsoft Unified Communications Managed API 3.0 (UCMA 3.0) in a Lync Server 2010 environment.
The UCMA application uses a Session Initiation Protocol (SIP) uniform resource identifier (URI) or a tel URI to create a user endpoint. The SIP URI is in the "user=phone" format.
The endpoint receives a call that is routed from a Mediation Server.
The call is connected.
In this scenario, the call is disconnected after 30 minutes because the SIP session is expired.
Note The session timer cannot be disabled or increased. If you set a lower value for the timer, the call will be disconnected after the timer you set.
This issue occurs because UCMA endpoint sends a 200 Response without a certain header to the update request from the MediationServer. After the call is connected, the Mediation Server sends a SIP UPDATE request to a UCMA endpoint to update the session. However, if the UCMA endpoint sends a 200 Response without a certain header to the request. This causes the Lync Server not to route the message correctly. Therefore, Mediation Server does not receive the response to the refresh request and disconnects the call.
To resolve the issue, install the following cumulative update:
2740406 Description of the cumulative update for Lync Server 2010, Unified Communications Managed API 3.0 Runtime: October 2012