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

Hi,

Yes. As Paul's conclusion of BCP, UAS should not include SDP after sending 
the ANSWER.

My talking is , even UAS violate the BCP suggestion, there's no normative 
problem.

Thanks,

Gao

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Christer Holmberg <[email protected]> 
2010-04-21 19:44

收件人
"[email protected]" <[email protected]>
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OKUMURA Shinji <[email protected]>, "[email protected]" 
<[email protected]>, "[email protected]" <[email protected]>
主题
RE: [Sipping] Is SDP in an unreliable response "the answer" ???







Hi, 

>> 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. 
> 
>                I guess "missunderstood as a new offer" issue is clear: 
>                If the session-id of o= line is the same the ANSWER, UAC 
can treate it as just COPY of the answer; 
>                If the session-id is higher than the ANSWER's session-id, 
the UAC can treate it as *new* offer. As the UAC MUST ignore any SDP after 
ANSWER, it is OK for UAC doing nothing. But if UAC checks the SDP and find 
it is 
>                *new* offer and violation of O/A rules then terminate the 
session, I also think it is also OK(UAS do bad behavior at first). 

I am not talking about the UAC procedure. I fully support saying that the 
UAC ignores the SDP.

My problem is to say that the UAS shall not include SDP, because the UAC 
could "missunderstand it as a new offer". All we need to say is that the 
UAS MUST NOT include a new SDP.
 
Regards,

Christer













                 > > -----Original Message-----
                 > > From: [email protected] 
                 > > [mailto:[email protected]] On Behalf Of 
OKUMURA Shinji
                 > > Sent: 21. huhtikuuta 2010 8:45
                 > > To: [email protected]
                 > > Subject: Re: [Sipping] Is SDP in an unreliable 
response "the 
                 > > answer" ???
                 > > 
                 > > Hi,
                 > > 
                 > > Hans Erik van Elburg <[email protected]> Tue, 
20 Apr 
                 > > 2010 21:53:17 +0200
                 > > >On Tue, Apr 20, 2010 at 3:47 PM, Paul Kyzivat 
                 > > <[email protected]> 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.
                 > > _______________________________________________
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                 > > This list is for NEW development of the application 
of SIP 
                 > > Use [email protected] for questions on 
current 
                 > > sip Use [email protected] for new developments of core SIP
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                 > _______________________________________________
                 > Sipping mailing list  
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                 > This list is for NEW development of the application of 
SIP
                 > Use [email protected] for questions on 
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