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

[Christer Holmberg <christer.holmberg@xxxxxxxxxxxx>]

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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