答复: RE: 答复: RE: non-200 response to PRACK (was: Re: PRACK: Change MUST requirement to include SDP offer in first reliable provisional response)

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"Christer Holmberg" <christer.holmberg@xxxxxxxxxxxx>

2009-04-07 18:36

收件人
<gao.yang2@xxxxxxxxxx>
抄送
<sipping-bounces@xxxxxxxx>, "Paul Kyzivat" <pkyzivat@xxxxxxxxx>, <sipping@xxxxxxxx>
主题
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   out of date and returns this table to the offerer in the answer.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.
 
>
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.
 
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:
sipping-bounces@xxxxxxxx [mailto:sipping-bounces@xxxxxxxx] On Behalf Of gao.yang2@xxxxxxxxxx
Sent:
Tuesday, April 07, 2009 4:33 AM
To:
Paul Kyzivat
Cc:
sipping-bounces@xxxxxxxx; sipping@xxxxxxxx; 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 <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: [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:* 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: [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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> 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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_______________________________________________
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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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