Call cannot get connected

Question

UCMA app receives an incoming call, but it cannot get connected.
the following is the states of that call:
Underlying call state changed from Incoming to Establishing
Underlying call state changed from Establishing to Terminating
Underlying call state changed from Terminating to Terminated
The following is the exception encountered:
Request is already terminated  FailureReason = 0 Microsoft.Rtc.Collaboration.CallOperationFailureException:Request is already terminated ---> Microsoft.Rtc.Collaboration.OfferAnswerException:Request is already terminated
   at Microsoft.Rtc.Signaling.SipAsyncResult`1.ThrowIfFailed()
   at Microsoft.Rtc.Collaboration.ComponentModel.MediaProvider.EndGetAnswerInternal(IAsyncResult result)
   at Microsoft.Rtc.Collaboration.Call.EstablishCoreAsyncResult.OfferAnswerRequestCompleted(IAsyncResult result) Detected at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
   at System.Environment.get_StackTrace()
   at Microsoft.Rtc.Signaling.RealTimeException..ctor(String message, Exception innerException)
   at Microsoft.Rtc.Collaboration.OfferAnswerException..ctor(OfferAnswerFailureReason reason, String message, Exception innerException, IEnumerable`1 signalingHeaders, DiagnosticsInformation diagnosticsInformation)
   at Microsoft.Rtc.Collaboration.AudioVideo.MediaSessionAgent.CreateOfferAnswerException(OfferAnswerFailureReason type, Exception e, UInt32 errorCode, RtpEndpoint endpointForDiagBlob)
   at Microsoft.Rtc.Collaboration.AudioVideo.MediaSessionAgent.TerminateAllPendingAsyncResults()
   at Microsoft.Rtc.Collaboration.AudioVideo.MediaSessionAgent.TerminateMediaSession(TerminateMediaSessionWorkitemAsyncResult workitem)
   at Microsoft.Rtc.Signaling.WorkitemQueue.ProcessItems()
   at Microsoft.Rtc.Signaling.SerializationQueue`1.ResumeProcessing()
   at Microsoft.Rtc.Signaling.SerializationQueue`1.ResumeProcessingCallback(Object state)
   at Microsoft.Rtc.Signaling.QueueWorkItemState.ExecuteWrappedMethod(WaitCallback method, Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
--- End of inner exception stack trace ---
   at Microsoft.Rtc.Signaling.SipAsyncResult`1.ThrowIfFailed()
   at Microsoft.Rtc.Signaling.Helper.EndAsyncOperation[T](Object owner, IAsyncResult result)
   at Microsoft.Rtc.Collaboration.Call.EndAcceptCore(IAsyncResult result)
Do you know what causes that exception?
I want to enable Lync Server Centralized Logging Services, which scenario should I run? The AlwaysOn Scenario?
Thank you.

Answer 1

Michael,
Those are not test calls but real calls made by our costumers.
The costumers dial the toll free number and the Internet service provider or SIP provider sends the call to our Lync pools. The call is cancelled a few seconds after it is initiated, sometimes 6 seconds, sometimes 9 seconds, sometimes 20 seconds or longer.
We called the costumers and made sure that it was not the costumer who hung up the call.
And we are also sure that an IP address outside our Lync pool sends the CANCEL request. Our system has been working well for a long time but the resent few months this kind of error happens almost everyday in the morning. When the error happens, some
of the calls cannot get connected and some of the calls are good, but the load of the Lync pool, UCMA app pool is not heavy. A few minutes later, everything becomes normal, no error happens.
How should we do the trouble shooting? Where should we focus on?  The SIP provider or Lync pool?
Thank you for your help.
Jrjack