Microsoft Lync A/V Authentication Issue
In one of our most recent Lync implementations we ran into some issues of long post-dial-delay (PDD) on internal, external (Federated or Edge) and PSTN calls. The PDD was in the range of 8-10 seconds consistently. After troubleshooting, tracing packets, and pulling logs we found the issue. The issue was between the A/V Authentication service (living on the Edge server on an internal DMZ) and the Front End and Mediation servers (collocated). One of the required ports for TURN/STUN was not being allowed. All other ports were allowed, but port 443 was not specifically allowed. So – if you are experiencing long PDD delays on inbound and outbound calls, verify your firewall rules. The root cause of the issue was a typo in the access policy on the firewall. Fun experience and always a great way to remember to CHECK THE BASICS FIRST!
Emilio Rivera, PEI