I came across an interesting scenario yesterday related to early media:

A calls B and an early media session is setup. If A decides to "cancel" the request with a BYE (instead of CANCEL), TM ignores this as a tear down of the transaction. After a timeout, TM sends a "408 request canceled" upstream and a CANCEL request downstream (to B). This happens even though the BYE was correctly routed (loose routing) to B and the 200OK routed back. Both UAs (A and B) behave as if the session has been correctly terminated. Kamailio (TM) however seems to think otherwise???

According to the SIP RFC, a UE MAY send either a BYE OR CANCEL with Early Media. (See section 15 of RFC3261 on page 88) - "The caller's UA MAY send a BYE for either confirmed or early dialogs, and the callee's UA MAY send a BYE on confirmed dialogs, but MUST NOT send a BYE on early dialogs."

Is this a known issue or should I look into it?

Cheers

Jason