[Sip-implementors] Can UAS send 200 OK final response before receiving PRACK for provisional response(without SDP body) ?

[Brett Tate]

Does this implies that UAS can send 200 OK final response to initial

INVITE

before receiving the PRACK for the unacknowledged provisional response
without SDP?

Yes.

If the above scenario is possible than when should UAS free the RPR
transaction as the RFC 3262 states that UAS should be able to process

the

PRACK for the unacknowledged provisional response even after sending the
final response.

My interpretation of the following is that the 64*T1 timer continues for
transaction cleanup even though retries should not continue. However, it
mostly depends upon how you interpret "prepared to process" in relation to
the infamous 2xx versus 481 paragraph. My interpretation is overly
influenced by RFC 5057 indicating to destroy the dialog usage upon
receiving PRACK 481 instead recommending behavior similar to CANCEL 481.

"If the UAS does send a
final response when reliable responses are still unacknowledged, it
SHOULD NOT continue to retransmit the unacknowledged reliable
provisional responses, but it MUST be prepared to process PRACK
requests for those outstanding responses."

"If a PRACK request is received by the UA core that does not match any
unacknowledged reliable provisional response, the UAS MUST respond to
the PRACK with a 481 response. If the PRACK does match an
unacknowledged reliable provisional response, it MUST be responded to
with a 2xx response. The UAS can be certain at this point that the
provisional response has been received in order. It SHOULD cease
retransmissions of the reliable provisional response, and MUST remove
it from the list of unacknowledged provisional responses."