Does the originate_timeout start as soon as the invite is sent? If we get a 180 ringing 6 seconds in, does it restart? How is post dial delay (PDD) handled in this case? Does that have to be added into the originate_timeout seconds?
We have some carriers that take several seconds (up to 10-12) to actually come back with a cause code, if we fail over to a new carrier it can mess things up if we get back a 503 10 seconds into a 20 second origination_timeout.