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Re: [Sipping] Is SDP in an unreliable response "the answer" ???



Do remember that there are certain cases where the UAC will not ignore it. These are the cases where the message containing original answer has not yet arrived or been lost, and the protocol has not yet recovered from that.

regards

Keith

> -----Original Message-----
> From: sipping-bounces@xxxxxxxx 
> [mailto:sipping-bounces@xxxxxxxx] On Behalf Of Christer Holmberg
> Sent: Tuesday, April 20, 2010 1:47 PM
> To: OKUMURA Shinji; sipping@xxxxxxxx
> Subject: Re: [Sipping] Is SDP in an unreliable response "the 
> answer" ???
> 
> 
> 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
> > 
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