A call is dropped when a media time-out occurs on the gateway side of the Office Communications Server 2007 R2, Mediation Server

On the Mediation Server for Microsoft Office Communications Server 2007 R2, a media time-out occurs. This time-out occurs if no Real-Time Transport Protocol (RTP) packets or Real-Time Transport Control Protocol (RTCP) packets are received for 30 seconds. When the Mediation Server interacts directly through Session Initiation Protocol (SIP) with Cisco CallManager (CCM), the following scenarios occur. In these scenarios, no RTP packets or RTCP packets are received for a call.

Scenario 1

For a call that is on hold, the direction attribute is inactive from the perspective of the Mediation Server and from the perspective of CCM. In this scenario, CCM does not send any RTP packets or RTCP packets. Existing Mediation Server code ignores the media time-out. Therefore, the call is not dropped.

Scenario 2

  • A CCM user joins in an Office Communications Server 2007 R2 conference and then mutes the telephone.
  • The direction attribute for the Mediation Server for the interaction with CCM is sendonly.
  • The direction attribute for the telephone is recvonly.

In this scenario, CCM does not send any RTP packets or RTCP packets while the telephone is muted. Therefore, the call is dropped after 30 seconds.

Scenario 3

An Office Communicator user calls a CCM user who is configured to use Cisco Unity voice mail. When the call is connected to Cisco Unity, the call obtains the original media packets from Cisco Unity. Then, the Office Communicator user is prompted to leave a voice mail. However, Cisco Unity does not send any RTP packets or RTCP packets when the Office Communicator user leaves a voice mail. Therefore, a media time-out occurs after 30 seconds. Then, the call is disconnected, and the Office Communicator user cannot leave a voice mail.

To resolve this problem, install the update that is described in the following article in the Microsoft Knowledge Base:
977937 

(http://support.microsoft.com/kb/977937/
)
Description of the cumulative update for Office Communications Server 2007 R2, Mediation Server: April 2010

After you install this update, the Mediation Server is configured to ignore media time-outs when the server interacts with gateway peers that do not support RTCP.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the “Applies to” section.
To make sure that the Mediation Server operates correctly with IP gateways that do not support RTCP, this fix adds a new configuration file setting to the Mediation Server. This configuration file setting is called GatewayIgnoreMediaTimeout. The default value for the GatewaySessionTimer key is False. Setting the GatewaySessionTimer key value to the nondefault value of True enables voice over Internet Protocol (VoIP) media sessions between the Mediation Server and the IP gateway without the expected RTCP response from the IP gateway. The configuration file is the MediationServerSvc.exe.config file. This file should be located in the same directory as the Mediation Server installation files. To find this directory, search for the Microsoft.RTC.MediationServerCore.dll file. 

Note By default, the Mediation Server is installed on drive Cat the following location:

C:Program FilesMicrosoft Office Communications Server 2007Mediation Server

If this file is set to ignore VoIP media timeouts for the gateway side of the Mediation Server, its contents are displayed as follows:

If the GatewayIgnoreMediaTimeout is set to True, the Mediation Server will automatically enable SIP session timers for the SIP signaling session that manages the VoIP communications between the Mediation Server and the IP gateway. The SIP session timers typically use a default value of 1,800 seconds (30 minutes) to make sure of a reasonable time-out period for the VIoP media session. To sustain VoIP media communications between the Mediation Server external interface and the IP gateway, add the GatewaySessionTimer key to the MediationServerSvc.exe.config file. The default value for the GatewaySessionTimer key is True. Setting the GatewaySessionTimer key value to the nondefault value of False enables VoIP media sessions between the Mediation Server and the IP gateway not to be ended by the SIP session timer. If this file is set to ignore media time-outs and SIP session time-outs for the gateway side of the Mediation Server, its contents will be displayed as follows:

 

For more information about SIP session time-outs, visit the following Internet Engineering Task Force (IETF) website:

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A call is dropped when a media time-out occurs on the gateway side of the Office Communications Server 2007 R2, Mediation Server

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