Re: [ws-rx] NEW ISSUE: Remove LastMessage

[Anish Karmarkar <Anish.Karmarkar@oracle.com>]

Our (Oracle) email server is having some problems (delays) with 
delivering external emails intermittently since yesterday. I'm therefore 
relying on the OASIS email archive [1], which is not very reliable 
(based on the complaints that I have seen on this list -- ironic given 
the work that this TC is doing ;-) ). Apologies if I missed emails in 
this thread that already repeat/refute the argument below.

I don't think we should remove the LastMessage marker, but not for the 
reasons that Marc is stating (security/consistency). I quite agree with 
Doug on the security/consistency part. The LastMessage marker serves a 
very important purpose:

Under non-failure/normal operating conditions, there would not be a 
CloseSequence message sent. The Sequence would start with CS/CSR 
messages followed by Seq/SeqAck/SeqNack/ReqForAck messages and end with 
TerminateSequence message. The TerminateSequence message does not 
contain the last sequence number and is a message that can get lost (is 
not reliable).

If the TerminateSequence message is not received by the RMD and the 
LastMessage marker is *not* present in the last message of the sequence, 
the RMD has to hang around and keep its resources around until it times 
out. Once it times out it is going to assume (incorrectly) an abnormal 
termination of the sequence (and perhaps take corrective action).

If the TerminateSequence message is not received by the RMD and the 
LastMessage marker *is* present in the last message of the sequence, the 
RMD knows that it is done with the sequence and has to only be around to 
receive the final terminate message (or request for acks/re-ack, if any 
ack was lost) and may free up some of its resources. In this case, the 
loss of the TerminateSequence message does not result in an abnormal 
termination of the sequence on the RMD side on time out and no 
corrective action is necessary on the RMD side.

If the LastMessage marker is removed, there is a possibility (when the 
TerminateSequence message is lost) that the RMD may abnormally terminate 
the sequence when in fact it is not necessary to do so.

Hope that makes sense.

Thx.

-Anish
--

[1] http://www.oasis-open.org/apps/org/workgroup/ws-rx/messages.php


Marc Goodner wrote:
> I’m not so sure. I need to think about this some more.
> 
>  
> 
> A couple of observations though. First removing this breaks at least one 
> point of consistency with the contributed spec. I suggest we think 
> carefully before doing that. Second I don’t see this as a “protocol 
> complexity” issue. While the Close operation could completely subsume 
> the LastMessage marker you can still use this marker today without using 
> Close at all. That seems valuable to retain as it provides a simpler 
> protocol interaction capability in normal circmstances.
> 
>  
> 
> I disagree that this should be removed because a security mechanism can 
> address part of the functionality. I might agree is the composition with 
> that security mechanism was actually defined. If that is part of the 
> rationale for this I suggest not doing this until we have that security 
> composition defined.
> 
>  
> 
> ------------------------------------------------------------------------
> 
> *From:* Jacques Durand [mailto:JDurand@us.fujitsu.com]
> *Sent:* Wednesday, November 02, 2005 10:47 AM
> *To:* 'Doug Davis'; ws-rx@lists.oasis-open.org
> *Subject:* RE: [ws-rx] NEW ISSUE: Remove LastMessage
> 
>  
> 
> +1
> 
> I thought about proposing this too. The new Close operation subsumes 
> almost completely the LastMessage marker  - the
> 
> added value is not worth the added protocol complexity.
> 
> -Jacques
> 
>  
> 
> ------------------------------------------------------------------------
> 
> *From:* Doug Davis [mailto:dug@us.ibm.com]
> *Sent:* Wednesday, November 02, 2005 7:30 AM
> *To:* ws-rx@lists.oasis-open.org
> *Subject:* [ws-rx] NEW ISSUE: Remove LastMessage
> 
>  
> 
> 
> Title:Remove LastMessage
> 
> Description:
> The LastMessage element, as part of a Sequence header element, appears 
> superfluous. It seems to serve 2 purposes:
> 1 - force a SeqAck to be sent back from the RMD
> 2 - force the RMD to reject any messages with a higher message #
> 
> #1 can be done with an AckReq header.  We should avoid having multiple 
> ways to do the same thing.
> #2 is really only an issue if someone tries to hijack the sequence - and 
> to protect against that we should be using a real security mechanism 
> like WS-SC/Trust, not the LastMessage element.
> 
> When an RMS is done with a sequence it is free to simply Close or 
> Terminate it (whether or not it has all of the Acks it wants - but 
> normally it will wait) - having an additional message exchange to send a 
> LastMessage is unnecessary.
> 
> Justification: See above.
> 
> Target: core
> 
> Proposal:  Remove all references to LastMessage (and related Fault) 
>  from the spec [1].  See attached diff/pdf file for the specific changes.
> 
> [1] 
> http://www.oasis-open.org/apps/org/workgroup/ws-rx/download.php/15001/wsrm-1.1-spec-wd-05.pdf 
> 
> 
> 
> Note the protocol flow/example picture was updated too.
>