[Sipping] 答复: Rollback issue: a proposal

1. Using your pic, but UPDATE(6)/200OK(7) with no Offer/Answer:

                 UAC                                          UAS
                  |                                            |
                  |-------------(1) INVITE SDP1--------------->|
                  |                                            |
                  |<------------(2) 200 OK SDP2----------------|
                  |                                            |
                  |------------------(3) ACK------------------>|
                  |                                            |
                  |                                            |
                  |-------------(4) INVITE SDP3--------------->|
                  |                                            |
                  |<----(5) 183 Session Progress SDP4----------|
                  |                                            |
                  |                                            |
                  |<------------(6) UPDATE --------------------|
                  |                                            |
                  |-------------(7) 200 OK ------------------->|
                  |                                            |
                  |<---------------(8) 200 OK------------------|
                  |                                            |
                  |------------------(9) ACK------------------>|
                  |                                            |

Dialog state before Re-INVITE: dialog;

Re-INVITE(4) want to refresh to state: dialog';

UPDATE(6) is a newer refresh: dialog''

200OK(7) is the commitment of dialog''. And 200OK(8) is just using the 
committed state(dialog'') if UAS want to commit the session modification. 
And this is defined in RFC3311: 

If a UA
   uses an UPDATE request or response to modify the remote target while
   an INVITE transaction is in progress, and it is a UAS for that INVITE
   transaction, it MUST place the same value into the Contact header
   field of the 2xx to the INVITE that it placed into the UPDATE request
   or response.

2. I think the same is for session modification if UPDATE(6)/200OK(7) with 
Offer/Answer. That is, if the Offer/Answer in UPDATE(6)/200OK(7) is a new 
modification. Then the modification MUST be committed by 200OK(7). Then, 
it has nothing to do with (8).

Only with specific definition, the Offer/Answer in UPDATE(6)/200OK(7) can 
be treated as part of the modification triggered by Re-INVITE. 
Precondition is one case.

3. About racing condtion.
My proposal has no racing condition. And in later e-mail, I will explain 
it specificly.

Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com> 
发件人:  sipping-bounces@ietf.org
2009-03-03 21:32

收件人
sipping <sipping@ietf.org>
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主题
[Sipping] Rollback issue: a proposal

Hi,

I have put together the following draft. It contains a proposal for the 
rollback issue that has been discussed on the list:

http://www.ietf.org/internet-drafts/draft-camarillo-sipping-reinvite-00.txt

I have also written another short draft on an issue related to 
preconditions that was also discussed on the list in one of the 
rollback-related threads:

http://www.ietf.org/internet-drafts/draft-camarillo-sipping-precons-00.txt

Comments are welcome.

Cheers,

Gonzalo
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