The case of the missing 200 OK...
I have added a new trunk provider to our 3800, and have a strange problem. An incoming call is properly established, (INVITE, 200 OK, ACK) and then the PBX sends a re-INVITE message back to update some caller ID info. Not a big deal, but the when the carrier replies, the SBC sees the 100 TRYING message, but not the 200 OK. Call then times out and drops.
The carrier confirms they are sending the 200 OK, and the packet trace on the SBC interface (via remote capture-receiver) shows the 200 OK. Wireshark identifies the 200 OK as part of the call in the VoIP tools. Call-ID and CSEQ numbers look fine. However, the SBC does not process the 200 OK, and the sipmsg.log and log.sipd do not even show it.