Lync Edge Server or Pool Server have uncommon call drops (30sec) and other IM issues
I came across a funny problem. I customer complained if a federated call was initiated the call always dropped after exactly 31 seconds. What we could figure out was this error message. SIP/2.0 504 Server time-out ms-client-diagnostics : 52085;reason="Dialog does not exist" So I continued the analysis and traced the calls. With the wonderful tool SNOOPER, I was able to get a see the "Call Flow Windows", which is really a very helpful visualization of the exact package flow. I saw now the SIP Session was initiated correctly. BUT I figured out, the PRACK message was not acknowledge, so the ACK 200/OK was missing. Even the message was send correctly the target host. "This is a kind of early media." The Voice stream is established, but need to be reconfirmed in case some port/ parameter should be changes/ optimized. Since the ACK is missing, truly the Lync Server must think the call has ended and actively dropped it. This all is happened on the...