What PRACK usages are we adding???
We are talking about being allowed to send a non-200
response to a PRACK, and how to deal with it.
Regards,
Christer
From: gao.yang2@xxxxxxxxxx [mailto:gao.yang2@xxxxxxxxxx]
Sent: 8. huhtikuuta 2009 8:23
To: Paul Kyzivat
Cc: Christer Holmberg; sipping@xxxxxxxx; sipping-bounces@xxxxxxxx; Rockson Li (zhengyli)
Subject: 答复: Re: 答复: Re: 答复: Re: PRACK: Change MUST requirement to include SDP offer in first reliable provisional response
Hi
inline:)
Paul Kyzivat <pkyzivat@xxxxxxxxx> 写于 2009-04-08 12:37:40:
>
>
> gao.yang2@xxxxxxxxxx wrote:
> >
> > I do not think it is naivety of RFC3262.
> >
> > In theory, there are cases that UAS(PRACK's UAS) should return non-2xx,
> > as there is no explicit regulation of what can be in PRACK or not.
> >
> > But as UAS MUST return 2xx, then we can *deduce* that it is UAC's
> > obligation to make sure UAS will accept the PRACK. If UAS do not obey
> > this, UAC can terminate the session. And if UAS want to issue a
> > modification of session which may be rejected by UAC, it can use UPDATE
> > later.
>
> You have an opinion of what the UAS needs to do to resolve the
> inadequacies of 3262, and I have a different opinion about that. That is
> why we are discussing it. And I expect there are yet other opinions.
> That is why we are discussing it.
>
> IMO there are cases where a non-2xx response is called for, and
> terminating the session is an unreasonable remedy. The one I have given
> is where an Authorization header is included but the nonce has expired.
> There is no other way for the UAC to learn that it needs a new nonce,
> and having the session fail in that case is unreasonable. I'm sure there
> are other cases as well.
>
[Gao] If we adding more usage to PARCK, I'm sure there are other cases as well too.
My point is that we can do the thing with another UPDATE, while not the PRACK.
I think this is not a dialectic problem, it is just choice. So, I would not stick to my personal ponit of view if people want to making PRACK with more usage.
> > Considering UAC, it can judge from the 4xx to terminate the session(such
> > as 481), or send a new PRACK.
>
> If you acknowledge that the UAS may have need to send a non-2xx
> response, and the UAC may then want to retransmit the PRACK, then it
> seems you are agreeing with me.
>
> > And the process mentioned above just obeys RFC3262, and it practical
> > enough for the usage.
> > I can accept the UAC *judging from the 4xx to terminate the session(such
> > as 481), or send a new PRACK. But I think considering the UAS rejecting
> > the PRACK and retransmiting 18x(100rel) would make the problem too
> > complex.
>
> What is so hard?
[Gao] No hard, just complex :)
>
> Thanks,
> Paul
>
> > Thanks
> > Gao
> >
> >
> >
> > *Paul Kyzivat <pkyzivat@xxxxxxxxx>*
> >
> > 2009-04-07 20:59
> >
> >
> > 收件人
> > gao.yang2@xxxxxxxxxx
> > 抄送
> > Christer Holmberg <christer.holmberg@xxxxxxxxxxxx>, sipping@xxxxxxxx,
> > sipping-bounces@xxxxxxxx, "Rockson Li (zhengyli)" <zhengyli@xxxxxxxxx>
> > 主题
> > Re: 答复: Re: PRACK: Change MUST requirement to include SDP
> > offer in first reliable provisional response
> >
> >
> >
> >
> >
> >
> >
> >
> > We could write in an RFC that lead must be turned into gold, but when it
> > came time to implement that it would be discovered that it wasn't
> > feasible to always follow the RFC.
> >
> > The quotes below reflect a similar degree of naivety in 3262, at least
> > regarding the responses to PRACK. Plenty of examples have been given of
> > cases where it is inappropriate to return a 200 response.
> >
> > The statement that retransmissions shall cease when the matching PRACK
> > is received is, IMO, predicated on the assumption that a 200 will always
> > be returned. Once you reverse that assumption, then you must also
> > reconsider this statement.
> >
> > Thanks,
> > Paul
> >
> >
> > gao.yang2@xxxxxxxxxx wrote:
> > >
> > > More points of view to this question:
> > >
> > > By RFC3262:
> > > 1. "Retransmissions of the reliable provisional response cease when a
> > > matching PRACK is received by the UA core."
> > >
> > > 2. "If the PRACK does match an unacknowledged reliable provisional
> > > response, it MUST be responded to
> > > with a 2xx response."
> > >
> > > So, when UAs receive a matching PRACK, it will stop re-transmit the
> > > reliable provisional response(18x). And the response
> > > to PRACK MUST be 2xx.
> > >
> > > It is simple and clear. And when UAs receive non-2xx response to PRACK,
> > > it is clear that the other side do not receive the
> > > PRACK. It can send a new PRACK(CSeq++, the same RAck).
> > >
> > > And now, we can use PRACK to send "precondition notification" and "codec
> > > refine". When we need to issue session modification like adding codec,
> > > adding/removing media streams, we MUST using Re-INVITE/UPDATE.
> > >
> > > I think we should not re-write RFC3262 to allow the UA to reject the
> > PRACK.
> > >
> > >
> > >
> > >
> > >
> > > *Paul Kyzivat <pkyzivat@xxxxxxxxx>*
> > > 发件人: sipping-bounces@xxxxxxxx
> > >
> > > 2009-04-06 20:16
> > >
> > >
> > > 收件人
> > > "Rockson Li (zhengyli)" <zhengyli@xxxxxxxxx>
> > > 抄送
> > > sipping@xxxxxxxx, Christer Holmberg
> > <christer.holmberg@xxxxxxxxxxxx>
> > > 主题
> > > Re: PRACK: Change MUST requirement to
> > include SDP offer in
> > > first reliable provisional response
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > I think I also agree. There are a lot of things that in hindsight we
> > > probably would have done differently. But that is water over the dam. We
> > > are where we are.
> > >
> > > Paul
> > >
> > > Rockson Li (zhengyli) wrote:
> > > > I totally agree with Hadriel's insight here.
> > > >
> > > > It should have been avoided to put too many jobs into PRACK,
> > > >
> > > > I miss KISS(Keep It Simple and Stupid) principle
> > > >
> > > >
> > > >
> > > > Regards,
> > > >
> > > > -Rockson
> > > >
> > > >
> > ------------------------------------------------------------------------
> > > > *From:* sipping-bounces@xxxxxxxx [mailto:sipping-bounces@xxxxxxxx] *On
> > > > Behalf Of *Hadriel Kaplan
> > > > *Sent:* Tuesday, March 31, 2009 9:50 PM
> > > > *To:* Christer Holmberg; sipping@xxxxxxxx
> > > > *Subject:* Re: PRACK: Change MUST requirement to include SDP
> > > > offer in first reliable provisional response
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > In hindsight I’m thinking we probably also shouldn’t have made the SDP
> > > > answer (or another offer) required or even possible in the PRACK
> > > > either. I think it should have been for one and only one purpose: to
> > > > acknowledge receipt of the provisional response.
> > > >
> > > >
> > > >
> > > > -hadriel
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > ------------------------------------------------------------------------
> > > >
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