Also RFC 3261 page 80
o Once the UAS has sent or received an answer to the initial
offer, it MUST NOT generate subsequent offers in any responses
to the initial INVITE.
Cheers
Shaun
Shaun Bharrat Sonus Networks
www.sonusnet.com The Voice of the New Public Network
>-----Original Message-----
>From: Christer Holmberg (JO/LMF)
>[mailto:[EMAIL PROTECTED]
>Sent: Thursday, January 22, 2004 1:30 PM
>To: 'Paul Kyzivat'
>Cc: Krishna Kanth T; [EMAIL PROTECTED]
>Subject: RE: [Sip-implementors] Few doubts in sip protocol
>
>
>
>Hi,
>
>Chapter 5 in RFC 3262 says:
>
>"If the UAC receives a reliable provisional response with an offer
>(this would occur if the UAC sent an INVITE without an offer, in
>which case the first reliable provisional response will contain the
>offer), it MUST generate an answer in the PRACK."
>
>To me this sounds like you can only receive an offer in a
>reliable response (which also must be the FIRST reliable
>response, said in the same chapter).
>
>The chapter also says:
>
>"If the INVITE contained an offer, the UAS MAY generate an answer in a
>reliable provisional response (assuming these are supported by the
>UAC)."
>
>To me this sounds that only an answer to the offer in the
>INVITE request can be sent in the reliable response.
>
>No, the text doesn't forbid other usage, and I do think it
>could be more clear, but at least what I've just written is my
>understanding of the text and previous discussions.
>
>Also, which I asked earlier, IF you're allowed to send new
>offers in provisional responses, what happens if I have sent
>you a new offer before that, which you yet haven't received
>when sending me your offer (ie we have a race condition). I
>can't send a 490 response to your provisional response, so do
>I have to accept your offer and ASSUME that you will reject my
>offer (which I sent in a request, eg UPDATE)?
>
>Regards,
>
>Christer Holmberg
>Ericsson Finland
>
>
>
>> -----Original Message-----
>> From: Paul Kyzivat [mailto:[EMAIL PROTECTED]
>> Sent: 22. tammikuuta 2004 20:01
>> To: Christer Holmberg (JO/LMF)
>> Cc: Krishna Kanth T; [EMAIL PROTECTED]
>> Subject: Re: [Sip-implementors] Few doubts in sip protocol
>>
>>
>> Christer,
>>
>> Once we get beyond 3261, adding 3262 and 3311, it no longer
>> makes sense
>> to talk about relating offers and answers to particular
>transactions,
>> because a single offer/answer pair can be split across multiple
>> transactions. It really only makes sense to think about the
>> offers and
>> answers in the context of dialog and independent of transactions.
>>
>> What is it that make you think you can't send multiple offers and/or
>> answers within a single transaction?
>>
>> If anybody shares this belief with you I would like to get it
>> resolved.
>>
>> It is my understanding that *in the presence of 100rel*, INVITE,
>> reliable provisional responses to invite, PRACKs, responses
>to PRACK,
>> UPDATEs, responses to UPDATES, and ACK all provide
>> opportunities to send
>> offers and answers, subject only obeying the offer/answer
>> protocol and
>> the rule that the first offer must be in INVITE or in first reliable
>> response to it. (Of course UPDATE can only be used if it is
>> also supported.)
>>
>> Paul
>>
>>
>> Christer Holmberg (JO/LMF) wrote:
>> > Hi,
>> >
>> > Comments inline ([CHH])
>> >
>> >
>> >>>[CHH] My understanding is that only the first reliable
>> >>>provisoinal response may contain an offer, and only in the
>> >>>case that the initial INVITE didn't contain one (in which the
>> >>>answer is sent in the first PRACK).
>> >>>
>> >>>I think that there can only be one offer/answer exchange
>> >>>per transaction, so once a SDP (offer or answer) has been
>> >>>sent in a provisional response no more can be sent for that
>> >>>transaction (INVITE). Or?
>> >>>
>> >>>IF we were allowed to send more offers in provisional
>> >>>responses, how would we handle race conditions if the UAC at
>> >>>the same time sends a new offer (we can't send 491 to a
>> >>>provisional response)?
>> >>>
>> >>
>> >>Well, RFC 3312 certainly calls for multiple offer/answer
>cycles per
>> >>INVITE. (It isn't really one transaction, since it requires
>> PRACK and
>> >>the prack is a separate transaction.)
>> >
>> >
>> > [CHH] Yes, but every 18x provisional response is part of
>> the INVITE transaction, and within that single transaction I
>> don't think you can send multiple offers and/or answers.
>> >
>> >
>> >>It is my understanding that once you take account of 3361,
>> 3362, 3364
>> >>and 3311, offer/answer has been decoupled from specific
>> >>messages. Within an invite dialog you may have a sequence
>> of offer/answer
>> >>exchanges. The main limitations are that each offer must be
>> answered and
>> >>that you can't send another offer until the prior one has
>> been answered.
>> >
>> >
>> > [CHH] I agree on that, but I still think you can't send
>> multiple offers and/or answers within a single transaction.
>> >
>> > Regards,
>> >
>> > Christer Holmberg
>> > Ericsson Finland
>> > _______________________________________________
>> > Sip-implementors mailing list
>> > [EMAIL PROTECTED]
>> > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
>> >
>>
>_______________________________________________
>Sip-implementors mailing list
>[EMAIL PROTECTED]
>http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
>
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
