[OpenSIPS-Users] ACK Timer

[Muhammad Shahzad]

Sorry i didn't see you are setting dialog timeout for sequential INVITE,
instead of initial INVITE, so this timeout would actually have no effect on
new call, it will effect only established call (e.g. when caller or callee
sets call on hold etc.) and when that sequential INVITE comes in the
destination has to accept it within 3 seconds, which is OK, since call is
already established, only its state being changed.

Secondly, a call is not considered established till ACK arrives from caller
party. Since caller never sends ACK, so destination should end call (after
32 seconds per RFC 3261) even if it does not receives CANCEL from caller.
And if destination receives CANCEL, then call should end anyway. Such call
can not be billed, since it was never established.