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



Hi,

<Dean Willis hat on>

Offer/answer is a mess. Instead, let's regard media as an application on top of SIP, and use an Info Package for negotiating the media. There is no connection to the SIP transactions, which means we don't need complicated rules on when and where to insert SDP, and we don't need to describe how offer/answer works for re-INVITEs etc.

<Dean Willis hat off>

I don't disagree with what people are saying, but trying to read it from a I-am-a-new-implementor-and-I-would-like-to-get-it-right-from-the-beginning perspective I don't think anything is clarified. Eg. talking about that an SDP sent after the answer would be "missunderstood as a new offer" is confusing. The important thing is not whether the UAS includes the UAS answer in subsequent responses or not, because the UAC still has to handle such situation. What is important is that the UAS MUST NOT send a *new* offer.

Regards,

Christer





 

> -----Original Message-----
> From: sipping-bounces@xxxxxxxx 
> [mailto:sipping-bounces@xxxxxxxx] On Behalf Of OKUMURA Shinji
> Sent: 21. huhtikuuta 2010 8:45
> To: sipping@xxxxxxxx
> Subject: Re: [Sipping] Is SDP in an unreliable response "the 
> answer" ???
> 
> Hi,
> 
> Hans Erik van Elburg <ietf.hanserik@xxxxxxxxx> Tue, 20 Apr 
> 2010 21:53:17 +0200
> >On Tue, Apr 20, 2010 at 3:47 PM, Paul Kyzivat 
> <pkyzivat@xxxxxxxxx> wrote:
> >> 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.
> >>
> >[HE] I miss what the UAC should do in this case for subsequent 
> >responses, does the following hold as well:
> >"If the UAC sent an offer in the INVITE, then after it receives SDP 
> >(the answer) in an unreliable response to the INVITE, any SDP in 
> >subsequent responses to the INVITE MUST be ignored/granted/... ." ?
> 
> I agree. And it's certainly "ignored".
> 
> >Regardless what the correct behaviour is, it is missing in 
> your summary.
> >
> >> - 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.
> >>
> >> 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.
> _______________________________________________
> 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
> 
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Use sip@xxxxxxxx for new developments of core SIP

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