Hi Paul, As long as the intermediates don't reject offers I don't think there should be a problem - as long as we can come up with some understandable rules, that is :) Regarding using media one is not being charged for, I agree with you. I don't think that has anything do to with this discussion. I can call you, being charged for audio (the SDP only contains audio), and we can verbally agree on what IP address/ports and codecs to use for video. If operators want to prevent that they need other mechanisms - offer/answer rules won't prevent it. Regards, Christer -----Original Message----- From: Paul Kyzivat [mailto:pkyzivat@xxxxxxxxx] Sent: Sunday, March 01, 2009 10:43 PM To: gaoyang Cc: Gonzalo Camarillo; gao.yang2@xxxxxxxxxx; sipping-bounces@xxxxxxxx; sipping@xxxxxxxx; Christer Holmberg Subject: Re: Closing the offer/answer rollback issue -- New drawbacks I just tried to catch up on the discussion here. I mostly see circular argument/counterargument with no changing of position. The only thing I have seen here that seems new is Gonzalo's proposal about "media in use". I see a lot of issues raised about UAs using media they are not being charged for. As Tom Taylor said, this is not a new argument, or unique to this situation. There is always the possibility that two UAs will attempt to communicate using media they did not signal in an obvious way in the signaling channel. If they succeed in doing so, it is presumably because they are using a media path that they have access to independent of the signaling. In that case the intermediary who feels it should be charging for this is simply hoping to charge for a service it is not providing, and so has no real grievance. The case where this might be a real problem is if a middlebox controls the media path (what resources are assigned, and whether media is / isn't permitted to flow), and yet the rules about session state are such that the middlebox and the endpoints have differing understandings of whether the active session includes a given media path or not. IMO that is the key issue that needs to be nailed down. Thanks, Paul gaoyang wrote: > > New drawbacks: > > 1. In the original mail, "in use" is after O/A and can be used. > In RFC3261, > If the session description has changed, the UAS > MUST adjust the session parameters accordingly, possibly *after asking > the user for confirmation*. > "*asking the user for confirmation*" can be user's preference(as Local > Policy). > > Then, the "in use" can be depend on "Local Policy". > > 2. As your original example: > some with precondition not OK, some without precondition or > precondition has been OK. > The modification part of the later(without precondition or > precondition has been OK) can need for "*asking the user for confirmation*". > > But the Re-INVITE failed for precondition not satisfied, and the user > will not be alerted or hinted. But the modification would go on beyond > user's idea. > > Another "Let alone" drawback, it is more serious than "rejected but > still let alone". > For "rejected but still let alone", user at least know what happened. > > 3. Partially comit and partially rollback of O/A which is considered atomic. > The impact is unknown now. > > > > > > Date: Fri, 27 Feb 2009 12:38:14 +0200 > From: > Gonzalo.Camarillo@xxxxxxxxxxxx > To: gao.yang2@xxxxxxxxxx > CC: > sipping-bounces@xxxxxxxx; sipping@xxxxxxxx; > christer.holmberg@xxxxxxxxxxxx > Subject: Re: 答复: Re: 答复: > Re: 答复: Re: ??: Re: ??: Re: > ??: Re: ??: Re: ??: Re: ??: Re: ??: Re: Closing the offer/answer > rollback issue > > Hi, > > at this point, the discussions are > going in circles and are not > productive any longer. No new ideas > are being introduced. > > > > I think I now understand your main points (media synchronization > and > session continuity) so that I can put together a more formal > description > of the straw-man proposal in my original email that > meets all the > requirements brought up here. > > > > The proposal will be what the WG had agreed on before with slight > > modifications (e.g., a clarification of the "in use" concept) in > order > to better address your concerns. > > > > Thanks for your input, > > > > Gonzalo > > > > gao.yang2@xxxxxxxxxx wrote: > > > > > > Yes. I think it is can, not MUST. > > > > > > And with precondition, the user can be hinted the new > modification just > > after Offer/Answer pairs. > > > > > > > > > > > > > > > *Gonzalo Camarillo <Gonzalo.Camarillo@xxxxxxxxxxxx>* > > > > > 2009-02-27 18:22 > > > > > > 收件人 > > > wang.libo@xxxxxxxxxx > > > 抄送 > > > christer.holmberg@xxxxxxxxxxxx, gao.yang2@xxxxxxxxxx, > sipping@xxxxxxxx, > > sipping-bounces@xxxxxxxx, Eric.wangxr@xxxxxxxxx > > > 主题 > > > Re: 答复: Re: 答复: Re: ??: Re: ??: Re: ??: Re: ??: Re: ??: > > > Re: ??: Re: ??: Re: Closing the offer/answer rollback issue > > > > > > > & gt; > > > > > > > > > > > Hi, > > > > UEB would have > rejected the video stream in the 183 response. > > > > > > Gonzalo > > > > > > wang.libo@xxxxxxxxxx wrote: > > > > > > > > HI, > > > > > > > > I think the video will be established.The figure below shows > the case. > > > > > > > > > > > > 1. REINVITE(audio，vedio) > > > > -----------------------------> > > > > 2. 183 > > > > <----------------------------- > > > > 3. PRACK/200 > > > > <------------------------------> > > > 4. UPDATE(audio，vedio) > > > > -----------------------------> > > > > 5. 200(audio，vedio) > > > > <----------------------------- > > > > > > > > 6. 4XX > > > > <----------------------------- > > > > > > > > After step 5, UEs' precondition are met ,and the video stream > is > > > established too. > > > > But UE-B send 4xx to reject 4XX (step 6). > > > > > > > > Regards. > > > > > > > > > > > > > > > > > > > > *Gonzalo Camarillo <Gonzalo.Camarillo@xxxxxxxxxxxx>* > > > > > > > 2009-02-27 17:30 > > > > > > > > > 收件人 > > > > wang.libo@xxxxxxxxxx > > > > 抄送 > > > > christer.holmberg@xxxxxxxxxxxx, > > gao.yang2@xxxxxxxxxx, > sipping@xxxxxxxx, > > > sipping-bounces@xxxxxxxx > > > 主题 > > > > Re: 答复: Re: ??: Re: ??: Re: ??: Re: ??: > > > Re: ??: Re: ??: > > > > Re: ??: Re: Closing the offer/answer rollback issue > > > > > > > > > > > > > > > ; > > > > > > > > > > > > > Hi, > > > > > > > > If UE-A wants to communicate with UE-B by video, but UE-B only > > > want to > > > > communicate by audio. > > > > > > > > then UE-B rejects the video stream and the video stream is > never > > > established. > > > > > > > > Cheers, > > > > > > > > Gonzalo > > > > > > > > > > > > -------------------------------------------------------- > > > > ZTE Information Security Notice: The information contained in > this > > mail is solely property of the sender's organization. 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