Re: Draft: Essential correction for re-INVITE rollback in RFC3261

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>Why we do not choose automatic fallback by two peer(UAC and UAS) to rollback to the state before Re-INVITE , while it has no ambiguous state of session. >(please refer to "draft-gaoyang-sipping-session-state-criterion-00") 
We were actually planning to choose full rollback (to the state before the re-INVITE), but then someone raised a race condition problem. I don't remember the name of the thread discussing that, though.
	>While automatic fallback has no fault, so I think it is no a better solution to use "manual fallback". 
See the thread about the race condition.

>1、"manual fallback" has race condition too, while the two peer issue its own Re-INVITE/UPDATE. And I think "manual fallback" is much more >like a refresh process. It may be a optional process, but it can not be the theoretical explanation. 
The protocol can deal with the case when two peers send re-INVITE/UPDATE.
The race condition (ok, maybe the wording is bad) was related to the fact that the UAS does not know whether an offer is sent before or after the UAC received the re-INVITE error response.

>2、I am glad to get your comments on "draft-gaoyang-sipping-session-state-criterion-00", which has the attitude that >there has no ambiguous state of session for unsuccessful Re-INVITE. >	>"draft-gaoyang-sipping-session-state-criterion-00" has no new definition or violation of current RFC, it is just clarification for >debate on the topic of "Commit/Rollback of Offer/Answer on Unsuccessful re-INVITE".   
Please try to look for the problem I mentioned above, and see whether you think it can be solved.

Regards,
Christer

								"Christer Holmberg" <christer.holmberg@xxxxxxxxxxxx> 
	2009-01-13 15:33 
				收件人		<gao.yang2@xxxxxxxxxx> 		抄送		"sipping LIST" <sipping@xxxxxxxx>, <sipping-bounces@xxxxxxxx> 		主题		RE: RE:  Draft: Essential correction for re-INVITE rollback in        RFC3261
		



	  	Hi, 	  	I agree that pre-conditions may be performed before the user is prompted, which may then cause the re-INVITE to fail. That was also previously discussed on the list. 	  	Now, if resources have been reserved, and the re-INVITE fails, there is nothing which prevents entities to release those resources. 	  	Also, if additional m- lines have been added, you will need to send a new re-INVITE/UPDATE to remove it. That's what we call a "manual fallback". 	  	Also, if you look at the old thread, there was a discussion about a possible race condition which could occur if you do a full fallback. 	  	Regards, 	  	Christer 	  	  	  		________________________________
	From: gao.yang2@xxxxxxxxxx [mailto:gao.yang2@xxxxxxxxxx] 	Sent: 13. tammikuuta 2009 2:43	To: Christer Holmberg	Cc: sipping LIST; sipping-bounces@xxxxxxxx	Subject: 答复: RE:  Draft: Essential correction for re-INVITE rollback in RFC3261			"draft-gaoyang-sipping-session-state-criterion-00.txt", clarify that there is no 	ambiguous state of session modification using current RFC definition. 	Just using current RFC definition, and without violation or new definition. 		My points of view: 		1、It should make the user have the capability to accept or refuse session modification 	(see "Intuitionistic(user point of view) requirement for rejecting session modification"). 		In my points of view, IMS(3GPP) as the multimedia platform, it should be enriched with 	this intuitionistic(user point of view) requirement. 		Considering precondition, it is always exchange offer/answer(and modified the session parameters) 	before prompting the end user. 		2、offer/answer is atomic, but it can be part of a nested transaction. Such as modification with precondition 	may have more than one offer/answer pair. So the modification is atomic, and the offer/answer is its part. 		If the precondition is not just about resource reservation(for example, two precondition, one about 	resource reservation, another about other application aspect). 	So when meeting precondition about resource reservation, the session parameters have been modified(sucessfully). 	But if the precondition about other application aspect is not meeted, this modification should be discard. 		So, how the application level will using the offer/answer as part of a nested transaction, is just beyond the offer/answer definition. 	And we should open the gate for the application level extention. 						"Christer Holmberg" <christer.holmberg@xxxxxxxxxxxx> 
	2009-01-12 18:08 
					收件人		<gao.yang2@xxxxxxxxxx> 		抄送		"sipping LIST" <sipping@xxxxxxxx>, <sipping-bounces@xxxxxxxx> 		主题		RE:  Draft: Essential correction for re-INVITE rollback in        RFC3261

		

					Hi, 			>1. 	>In "draft-ietf-sipping-sip-offeranswer-08.txt ", there is a use case: 	>The case of 	>adding a new media (like adding video to audio only session) which 	>requires permission from the peer through some user interaction is 	>one example. 	>From the user's viewpoint, he(or she) just reject the modification of session, so 	>the offer/answer should be rollback. 	>So, "any session	>parameters that have been sucessfully changed during the duration of	>the re-INVITE transaction MUST remain unchanged" is not reasonable for all 	>application use case. 			We have agreed that we cannot define different rules for different use-cases. We need to have a generic rule, and implementors shall then use that.		There was a long discussion on which solution to go for, and the text now reflects the agreed solution (which we also informed 3GPP about).		Regards,		Christer			               	               	               2. 	               There are nested transactions concept in application level above of offer/answer 	               which use a offer/answer pair as a sub-transaction. So, commit/rollback is not just 	               offer/answer issue, it is a application issue(such as precondition may have more than 	               one offer/answer pairs).And application level usage of offer/answer should be open for 	               the future extension. 	               	               3. 	               I just submitted a draft talking about session state 2009-01-08: 	               	               https://datatracker.ietf.org/idst/status.cgi?submission_id=11690 	               	               the document URL: 	               	               http://www.ietf.org/proceedings/staging/draft-gaoyang-sipping-session-state-criterion-00.txt 	               	               (the URL "http://www.ietf.org/proceedings/staging/draft-gaoyang-sipping-session-state-criterion-01.txt"; 	               is not available, but the 00.txt is the current one) 	               	               	               	               	               	               "Christer Holmberg" <christer.holmberg@xxxxxxxxxxxx> 	               发件人:  sipping-bounces@xxxxxxxx 		               2009-01-09 17:32 		                                	                                收件人	                                "sipping LIST" <sipping@xxxxxxxx> 	                                抄送	                                	                                主题	                                 Draft: Essential correction for re-INVITE rollback in        RFC3261		                                						               Hi, 		               I've put together the first version of the draft related to the re-INVITE follback fix, based on the agreed solution. 		               I had some problems with the IETF submission tool, but the draft can be found at: 		               http://users.piuha.net/cholmber/drafts/draft-holmberg-sipping-reinvite-rollback-00.txt <http://users.piuha.net/cholmber/drafts/draft-holmberg-sipping-reinvite-rollback-00.txt>  		               Regards, 		               Christer _______________________________________________	               Sipping mailing list  https://www.ietf.org/mailman/listinfo/sipping	               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 		               	               	               --------------------------------------------------------	               ZTE Information Security Notice: The information contained in this mail is solely property of the sender's organization. This mail communication is confidential. 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