On Tue, 2008-11-25 at 17:16 +0000, Gabor Paller wrote: > " I believe that you're just seeing the normal 20-second expiration of > the > branch." > > This is probably true. > > " The other one is not CANCELed because it sent SDP - this > triggers some exception handling because early media sessions are > sometimes used by PSTN gateways for extended periods of time." > > Are the rules of this exception handling public? I am curious, after how > much time the branch with SDP would be CANCELed.
It won't be. This is a well-known (if poorly documented) problem. There are IVR systems out there in the PSTN that use early media to send back prompts and collect digits, while never actually completing the call setup. When such a call is established through a SIP/PSTN gateway, it shows up as a 18x response to the INVITE with SDP. By normal SIP rules, such an early dialog would be torn down at some (implementation-defined) expiration time when a 2xx failed to appear. But if (when, actually, since long ago it did) our proxy tore down such a call, your perfectly functional IVR session would be cut off. So, we treat a 18x response with SDP as equivalent (for timeout purposes) to a 2xx response. _______________________________________________ sipx-users mailing list [email protected] List Archive: http://list.sipfoundry.org/archive/sipx-users Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users
