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Subject: RE: [ws-rx] New proposal for i019 and i1028

Thanks for the explanation. I have some more questions.
I am trying to evaluate the proposal with respect to the problem it is intending to solve. Is it fair to say that the intent of the Cancel proposal is to enable recovery without terminating (or more precisely needing to abort from RMS perspective) a sequence when there are problems? In this regard, can you clarify whether Filling the gaps is intended to be used specifically for recovery? For example, after a cancellation of a set of messages occur, the RMD notifies with the cancellation ack. If the RMS decides to fill the gap for those messages that have already been cancelled, it seems that RMS is allowed to resend those cancelled messages to fill the gaps and hence the allows those messages that were cancelled to be retransmitted. Did I get this right? 
If my previous assumption is correct,  it is not clear to me what happens when CancelAck and SequenceFill are out of sync. Could you clarify?
Again, if my assumptions/understanding is correct, is it fair to say that you are trying not to close a sequence but patch the problem with additional exchanges?
It helps me understand better if I understand the higher level motivation for the design.
Thanks again,

From: Stefan Batres [mailto:stefanba@microsoft.com]
Sent: Tuesday, Sep 13, 2005 6:56 PM
To: Yalcinalp, Umit; ws-rx@lists.oasis-open.org
Subject: RE: [ws-rx] New proposal for i019 and i1028



Thanks for taking the time to review this new proposal. First off I’ll give the two proposals names in an effort to simplify the discussion. I’ll call Doug’s proposal the “Close/FinalAck” proposal and I’ll call this new proposal the “Cancel” proposal.


Close/FinalAck and Cancel are not functionally equivalent. Cancel allows for the same semantics as Close/FinalAck and provides a separate and more general mechanism for resolving doubt.


As you mention, the fundamental problem with the spec today is the lack of a mechanism for resolving doubt. In the Close/FinalAck proposal it is necessary to end a sequence in order to resolve doubt, even if there is only a single message that can’t be transmitted. While that is adequate to address i019 and i028 as they are worded, it conflates the acts of ending a sequence and resolving doubt. The Cancel proposal allows for doubt resolution independent of whether a sequence is ended or not. Cancel can be composed with the existing sequence termination mechanism to achieve the same result as Close/FinalAck; ending a sequence with a final and accurate ack set.


Also note that the Cancel proposal maintains the spec as is in that there is one way to close a sequence and it remains unchanged.






From: Yalcinalp, Umit [mailto:umit.yalcinalp@sap.com]
Sent: Tuesday, September 13, 2005 6:01 PM
To: Stefan Batres; ws-rx@lists.oasis-open.org
Subject: RE: [ws-rx] New proposal for i019 and i1028


Hi Stefan,


Maybe I am looking at this in a simplistic way, but I can not follow the issue you have with the current proposal and how the alternate proposal addresses the issue.


It seems to me the fundemantal problem is for the RMS to determine the state of the RMD (thus resolving doubt) Thus, if the RMD were to send the final acknowledgement along with the ack ranges that indicate the messages that are received by the RMD, RMS has enough information to reconcile its own status with the RMD (basically it can diff the sequence numbers to obtain those messages which were in doubt but confirmed to be received by the RMD per the final ack). I am not clear as to why we need to do more here.


Perhaps you can clarify for me why your proposal is a better proposal and what the problem that Doug's proposal is not solving. It seems to me that in both cases the protocol is changed, but the proposal you are making is more complicated but functionally equivalent. I would like to understand the motivation for the complexity.







From: Stefan Batres [mailto:stefanba@microsoft.com]
Sent: Tuesday, Sep 13, 2005 12:50 PM
To: ws-rx@lists.oasis-open.org
Subject: [ws-rx] New proposal for i019 and i1028



After much discussion Doug has managed to make me understand his reasons for proposing his Close/FinalAck mechanism for addressing i019 and i028. We now agree, an accurate acknowledgement state can be helpful in order to resolve doubt and in addition, for cases where a sequence must be ended, that acknowledgement state must be final. These are preconditions for recovery and the protocol can aid in establishing these preconditions.


However, we still have an issue with the current proposal [1]. We think it conflates the notions of resolving doubt and closing sequences. Attached is an alternate proposal that we believe addresses this issue, allows for the exact semantics [1] provides and has other advantages. Details are in the document.


[1] http://www.oasis-open.org/apps/org/workgroup/ws-rx/email/archives/200509/msg00084.html


I look forward to the group’s comments.






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