Re: [Sipping] Summary of Closing the offer/answer rollback issue?

[OKUMURA Shinji <shin at softfront.co.jp>]

Hi,

comment inline.

"Ian Elz" <ian.elz at ericsson.com>
>Shinji,
>
>The summary that you have given provides a simple view of the issues.
>
>It does however highlight some other issues which need to be clarified.
>
>If I assume that your use of met/notmet refers to precondition
>negotiation then the sequence you have described highlights some
>specific issues.
>
>Here is a numbered copy of your sequence:
>
>   signaling            | O/A state                      | media in use
>   ---------------------+--------------------------------+--------------
>1. init-INVITE/200/ACK  | audio1(met)                    | audio1
>2. re-INVITE/183-rel    | audio2(notmet)                 | audio1
>3. (PRACK/200OK)        | audio2(met)    +video1(notmet) | audio2
>4. UPDATE/200OK         | audio2(met)    +video1(met)    | audio2+video1
>5. UPDATE/200OK         | audio2(met)    +video2(notmet) | audio2+video1
>   4xx/ACK              |                                |
>     Gonzalo's proposal | audio2         +video1         |
>     Gao's proposal     | audio1         +video1(?)      |
>
>1. This is OK. The original SDP offer/answer is agreed.
>
>2. In the re-INVITE the audio stream is being modified in some way. How
>this is being modified will result in whether preconditions are
>required.
>
>3. This creates an issue. The PRACK has made a new SDP offer as part of
>the precondition notification AND has also added a new media stream.
>
>I am unsure if this should be allowed during a precondition negotiation.
>Technically it is allowed but is does cloud the issue. Gao has stated in
>a separate response that the UPDATE (5.) should be rejected 504, and I
>agree with this, but as 3. is a PRACK I am unsure how this modified
>offer can be rejected. I would think that the receiving UA should reject
>the re-INVITE at this point.
>
>A simpler scenario would be:
>
>signaling            | O/A state                      | media in use
>---------------------+--------------------------------+--------------
>init-INVITE/200/ACK  | audio1(met)                    | audio1
>re-INVITE/183-rel    | audio1(met)    +video1(notmet) | audio1
>(PRACK/200OK)        | [no sdp]                       | audio1
>UPDATE/200OK         | audio1(met)    +video1(met)    | audio1+video1
>4xx/ACK              |                                |
>Gonzalo's proposal(?)| audio1         +video1         |
>Gao's proposal(?)    | audio1                         |
>
>I think that the end state should be to return the media back to state
>in which it was prior to the re-INVITE.

that is full-rollback, isn't it?
I like it, too.

>The question is how.
>
>The other issue that you have raised concerning new modification of the
>SDP during the precondition modification also needs to be addressed. My
>belief is that this modification should be rejected.

agree

> If the UPDATE with
>this modification crosses with the 4xx to the re-INVITE then we are back
>to the original issue from section 6.2 of the offeranswer draft. How
>does the UAS determine that this transaction is associated with the
>original re-INVITE or is a separate standalone transaction?

it seems to impossible.

>Offer/answer 5 in your original sequence is a modification to an agreed
>media stream and requires new precondition negotiation. While
>technically this is possible using UPDATE transactions I do not believe
>that this should be allowed. Any SDP modification using preconditions
>should require use of a re-INVITE.

I think so too.

>Ian Elz
>
>-----Original Message-----
>From: sipping-bounces at ietf.org [mailto:sipping-bounces at ietf.org] On
>Behalf Of OKUMURA Shinji
>Sent: 02 March 2009 09:44
>To: sipping
>Cc: Gonzalo Camarillo; Christer Holmberg
>Subject: Re: [Sipping] Summary of Closing the offer/answer rollback issue?
>
>Hi,
>
>The following table describes my understanding.
>Is this right?
>
>signaling            | O/A state                      | media in use
>---------------------+--------------------------------+--------------
>init-INVITE/200/ACK  | audio1(met)                    | audio1
>re-INVITE/183-rel    | audio2(notmet)                 | audio1
>(PRACK/200OK)        | audio2(met)    +video1(notmet) | audio2
>UPDATE/200OK         | audio2(met)    +video1(met)    | audio2+video1
>UPDATE/200OK         | audio2(met)    +video2(notmet) | audio2+video1
>4xx/ACK              |                                |
>  Gonzalo's proposal | audio2         +video1         |
>  Gao's proposal     | audio1         +video1(?)      |
>
>
>Regards,
>Shinji