"Christer Holmberg" <[email protected]>
2009-04-07 19:33
收件人
<[email protected]>
抄送
"Paul Kyzivat" <[email protected]>, <[email protected]>,
<[email protected]>
主题
RE: RE: [Sipping] 答复: RE: non-200 response to PRACK (was: Re: PRACK:
Change MUST requirement to include SDP offer in first reliable provisional
response)
Hi,
>>I mean rejectable in app-level. 491 is beneath app-level.
>> And precondition notification is not a rejectable usage in app-level.
>
>Ok, so where is all that defined?
>
>[Gao] By RFC3312: The offerer generates a transaction
> status table, identical to its local status table, and sends it to
> the answerer in the offer. The answerer uses the information of this
> transaction status table to update its local status table. The
> answerer also updates the transaction status table fields that were
> out of date and returns this table to the offerer in the answer. The
> offerer can then update its local status table with the information
> received in the answer. After this offer/answer exchange, the local
> status tables of both user agents are synchronised.
>
>The precondition state is just notification/updating, not negotiating.
And where is it said that a notification/updating request cannot be
rejected?
I have nothing against recommending that PRACKs are only used for
notifications etc, but I don't think that will ensure that a PRACK is
never rejected.
[Gao] RFC3262 defines that when UA recv PRACK, it must send 2xx. As
RFC3262 defined so, UA MUST NOT send PRACK with rejectable usage.
And as "draft-ietf-sipping-sip-offeranswer" recommending that PRACKs are
only used for usage that would not be rejected, I think thing is OK.
>>BTW, I saw some points of view (just today and yesterday) which want to
make it simple.
>
>I also want to make it simple.
>
>Saying that something must never happen is a very simple solution. We
sould do that for other things also, and our specs would become very
short... :)
>
>[Gao] I am not sure we are talking the same thing :)
>I mean that some people do not want modification here.
I am only talking based on agreements we have made. If the group decides
to change those agreements - fine.
[Gao] OK.
Regards,
Christer
Hi,
>>I think we already a while ago agreed on the principle that it shall be
possible to send a non-200 response to a PRACK (not only for offer/answer,
but possibly also due to other reasons).
>
>[Gao] Then, it is a modification of RFC3262.
Yes.
>And, in that case, why would an intermeidate be allowed to reject a
PRACK, but not the UAS?
>
>[Gao] I think, by RFC3262, it is not suitable to put too much usage in
the PRACK to make it rejectable.
Every request is rejectable, no matter how much or little usage you have
in it.
Regards,
Christer
From: [email protected] [mailto:[email protected]] On Behalf
Of [email protected]
Sent: Tuesday, April 07, 2009 4:33 AM
To: Paul Kyzivat
Cc: [email protected]; [email protected]; Christer Holmberg
Subject: [Sipping] 答复: Re: PRACK: Change MUST requirement to include SDP
offer in first reliable provisional response
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 <[email protected]>
发件人: [email protected]
2009-04-06 20:16
收件人
"Rockson Li (zhengyli)" <[email protected]>
抄送
[email protected], Christer Holmberg <[email protected]>
主题
Re: [Sipping] 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:* [email protected] [mailto:[email protected]] *On
> Behalf Of *Hadriel Kaplan
> *Sent:* Tuesday, March 31, 2009 9:50 PM
> *To:* Christer Holmberg; [email protected]
> *Subject:* Re: [Sipping] 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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