I had a customer today struggling with an issue where certain incoming calls were being automatically dropped after around 30 seconds. They did some debugging and found the solution that I thought I’d share.
In this case it only affected incoming calls to an IVR, but I’ve since read other reports of it affecting certain outgoing calls. It’s caused by a call provider ignoring SIP UPDATE messages sent by Asterisk. After a certain number of these messages are ignored the call gets disconnected.
You can only really tell if this is the cause of the call being disconnected by capturing the SIP packets and checking what’s going on but the SIP UPDATE messages can be disabled in Asterisk by adding –
to the SIP trunk in question.
At least 2 providers that seem to do this are CallCentric and Spitfire. For more information see here – http://forums.asterisk.org/viewtopic.php?f=1&t=80237
Another possible cause of calls dropping are SIP session timers