wang.libo@xxxxxxxxxx wrote: > > > > >>>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. 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. Thanks, Paul _______________________________________________ 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
