Hi Paul, I've changed the subject, because I don't think this is related to the re-transmission of 18x. It is a little related to the discussion about relaxing the must-insert-SDP-in-first-reliable-18x, but let's still have a separate thread for it. > > > > > >>>Is the flows below valid according to recent arguments? > > > > > >>> > > > > > >>> UAC UAS > > > > > >>> |----invite(SDP)--->| > > > > > >>> |<--- 183(SDP)------| > > > > > >>> |-----prack(SDP)--->| > > > > > >>> |<--- 200(SDP)------| > > > > > >>> > > > > > >>> flow 1 > > > > > Does it means,the first flow is allowed? > > > > > > Yes. > > > > I think, the restriction the first reliable response > must contain > > SDP if > > the INVITE without SDP > > should restrict the called > > user. > > > > > > That's the way it is now. > > > > >>Sure, I means, the first reliable response from the called >>user must contain NORMAL SESSION SDP in order to communication,but >>AS(application server) shouldn't be restricted by this rule >>as AS may only concern about early-session for pronunciation. Or, the >>AS is also restricted if early-session plays the same role as normal session. > >The AS is an artifact of IMS, it has no role in any of the >ietf standards. It has been expected that components playing >various roles such as this are bound by normal distinctions >between UAC, UAS, Proxy, etc. > >IMO it isn't a good idea to introduce a new kind of UA (or >proxy) that is bound by different rules. I don't think a new role is proposed. The AS was just an example, but from a SIP perspective it is of course behaving as a UAS in this case :) >You might consider the "early-session" mechanism specified by RFC 3959. >But I have never heard of it being implemented, so it may not be useful to you. I have been assuming that we ARE talking about the 3959 mechanism, and the question has been whether an "early-session" SDP offer fullfills the MUST rule to include SDP offer in the first reliable response. IF we decide to relax the rule I guess it doesn't really matter, but if we maintain the rule I guess it is a valid question. Regards, Christer _______________________________________________ Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping This list is for NEW development of the application of SIP Use sip-implementors@xxxxxxxxxxxxxxx for questions on current sip Use sip@xxxxxxxx for new developments of core SIP
