Paul, Paul Kyzivat <pkyzivat@xxxxxxxxx> Tue, 20 Apr 2010 09:47:58 -0400 >Here is my attempt at summarizing the discussion conclusions: > >Normative things (stated or implied in existing RFCs): > >- If the UAC sent an offer in the INVITE, then after it receives SDP >(the answer) in a reliable response to the INVITE, any SDP in subsequent >responses to the INVITE MUST be ignored. > >- Further, if SDP is received in an unreliable response to the invite >prior to receiving SDP in a reliable response, then it MUST be treated >as the answer for purposes of media processing, but not for purposes of >determining when another offer may be sent or received. > >- if the UAS receives an offer in the INVITE, it MUST NOT include SDP in >any response it sends until it has determined the intended answer SDP to >the offer. > >- once the intended answer SDP is determined, it MUST be sent in a >reliable response to the INVITE. It MAY be sent in one or more >*preceding* unreliable provisional responses. I agree. But I think one more sentence is necessary. - And the SDP in a *preceding* unreliable provisional responses to the INVITE MUST be identical to an answer SDP. >Non-normative, best practice suggestions: > >- if the UAS receives an offer in the invite, once it has sent the >answer in a reliable response, it should not send any SDP in subsequent >responses to the INVITE. I agree. And I add one more reason why it is necessary. 4. To avoid misunderstanding that UAS is sending new offer. Regards, Shinji > Thanks, > Paul > >Christer Holmberg wrote: >> Hi, >> >>>>> Before sending an answer, >>>>> - An UAS MAY send unreliable provisional responses with a SDP. >>>>> - And the SDP MUST be identical to an answer SDP. >>>>> >>>>> After sending an answer, >>>>> - The UAS should not insert a SDP in any response. >>>>> >>>>> Is this OK? >>>> That text still doesn't say what an SDP inserted after sending the >>>> answer means, only that it should not be sent. >>> The SDP means nothing. it is neither an offer nor an answer. >> >> Exactly. In my opinion that is what is important - not whether >> the UAS inserts SDP or not. >> >>>> I still don't see why we need to make a separation about SDP sent >>>> before and after the answer, because in both cases the SDP must be >>>> identical to the answer. >>> 1. RFC3261 says that UAS MAY send it before the answer and >>> doesn't say nothing after the answer. >> >> That is one reason why we are writing the draft - to clarify >> things which may not be clear in the specs. >> >>> 2. The SDP MUST be ignored by UAC. it is meaningless. >> >> I agree, and that is what we must be clear about. Because, >> as we know, some people want to send a NEW offer (or updated >> answer) in a subsequent response, and that is not allowed. >> >> >>> 3. if another o/a exchange is occured (using UPDATE or PRACK), >>> it is not even a confirmation. >>> >>> And, again, I know there are many implementations that send >>> a copy of the SDP after the SDP answer has been sent, so instead of >>> saying that it should not be done I think it is much more important to >>> say that, if it is done, it must be identical to the SDP answer. In other >>> words, to make it clear that the UAS can not send a NEW offer (or >>> updated answer) in a subsequent response after the SDP answer has been sent. >>> >>> Since UAC MUST ignored it, there is no problem on a interworking. >>> Why must it be identical to the SDP answer? >> >> Well, if you look at it that way, fine. But, then the important >> thing is that the UAC must ignore it - not that the UAS should >> not send it. >> >> Regards, >> >> Christer >> >> >> >> >>>> Regards, >>>> >>>> Christer >>>> >>>> Hans Erik van Elburg <ietf.hanserik@xxxxxxxxx> Mon, 19 Apr 2010 >>>> 13:55:41 +0200 >>>>>> - An UAS MAY insert a SDP body that is identical to the SDP answer, >>>>>> in an unreliable provisional response before the SDP answer has >>>>>> been sent. >>>>>> >>>>>> - The UAS MUST NOT insert a SDP body that is not identical to the >>>>>> SDP answer, in an unreliable provisional response before the SDP >>>>>> answer has been sent. >>>>>> >>>>> This is terribly confusing. Very probabe that noone will get it right. >>>>> Triple negation. And talking about sending and answer before the >>>>> answer has been sent. ??? >>>>> >>>>> >>>>>> - The UAS MUST NOT insert a SDP body in any response after the SDP >>>>>> answer has been sent. >>>>>> >>>>> This means that you can't send it again after you've send it in an >>>>> unreliable provisional response. Do you want tto say that? >>>>> >>>>> /Hans Erik van Elburg _______________________________________________ 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
