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>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of Brett Tate
>Sent: Tuesday, February 16, 2010 3:11 PM
>To: Aneesh Naik
>Cc: [email protected]
>Subject: Re: [Sip-implementors] rfc3262: PRACK 481 response during race
>condition with INVITE 2xx
>
<snip>
>Processing the late PRACK and having to send 200 OK are two separate
>things. One of the common debates/ambiguities concerning rfc3262
>relates to some interpreting the RFC in a way which usually requires
>sending 200 responses. It has been and continues to be debated.>
>
>RFC 3262 section 3 indicates: "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."
>
>I'm attempting to find out if it is acceptable to send 481 response
>for unacknowledged reliable response's PRACK when the dialog still
>exists. However the answer likely falls within the typical 200
>response debate. Those that think the 200 typically needs to be sent
>would say that the 200 needs to be sent for the late PRACK if received
>within 64*T1 (or even not apply the 64*T1 limit). Those that don't
>think 200 is typically needed would say that a 481 can be sent since a
>200 is misleading if unwilling to fully update things per late PRACK's
>headers/content.
>
>
>> > The relevance is mainly associated with somehow trying to communicate
>> > unwillingness to fully update the dialog per PRACK's headers/content
>> > because of race condition.
>>
>> From RFC 3261: "If the PRACK contained a session description, it is
>> processed as described in Section 5 of this document. If the PRACK
>> instead contained any other type of body, the body is treated in
>> the same way that body in an ACK would be treated.".
>>
>> So, 481 cannot be the response in your case.
>
>I'm not sure that I understand the relevance of your RFC 3261 (actually RFC
>3262)
>quote in supporting opinion that 481 can't be sent.
>
I'm not sure if this was mentioned before, but 3262 clearly states that you
MUST send 2xx:
"If the PRACK does match an unacknowledged reliable provisional
response, it MUST be responded to with a 2xx response."
But I guess that's part of the debate you speak of.
If one follows the guidance in RFC 5057, then a 481 would destroy the
INVITE usage for the dialog and likely the dialog since that's
probably its only usage.
It seems to me that RFC 3262 ought to have allowed a 488 response if the
headers/content of the PRACK were not acceptable. Theoretically, this
would cause the UAC to revert to the previous state (e.g. SDP session
parameters).
cheers,
(-:bob
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