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Subject: RE: [ws-rx] i144 - Editorial (maybe) RMS MessageNumberRollover behaviorunclear

Comments in line.

"Bob Freund-Hitachi" <bob.freund@hitachisoftware.com>

07/05/2006 12:36 PM

Doug Davis/Raleigh/IBM@IBMUS, <ws-rx@lists.oasis-open.org>
RE: [ws-rx] i144 - Editorial (maybe) RMS MessageNumberRollover behavior unclear

Comments in line:

From: Doug Davis [mailto:dug@us.ibm.com]
Wednesday, July 05, 2006 10:33 AM
[ws-rx] i144 - Editorial (maybe) RMS MessageNumberRollover behavior unclear




 Just to get the discussion going on this (again), I would prefer to close this with no action.  Your two questions:

1) It is unclear under what circumstances the RM Source generates a MessageNumberRollover fault

2) Assuming that the RM Destination Transmits a MessageNumberRollover fault upon receipt of a message with a MessageNumber that exceeds its internal limitations or the big number cited, whichever happens first, what mechanism is used by the RM Source to close or terminate the sequence?

Are either already covered in the spec or are implementation choices/details that the spec should not dictate.

For (1) the RMS may choose to generate this if the AS asks to use a msg# that is too big.  But this is not something the spec can (or should) have any say over.  This is not something that would appear on the wire and is an issue between the AS and the RMS.  I would point out that in the case of the AS trying to use a msg # that is too big (if the RMS allows the AS this choice at all), could result in some other fault too.  Since the RM spec deals with just faults related to the RM protocol, and this fault is not necessarily an RM protocol fault, there is no reason to mandate a specific fault for this condition.

No, this fault when generated by the RM Source is not likely a wire level event, but the spec says (June 27 version of WD 15) on line 583 that the “RM Source or Destination MUST generate a MessageNumberRollover fault”.  Should that text be changed to reflect your assertion?

Hmmm, interesting.  I wonder what the original intent of the RMS generating that Fault was for.  If I'm wrong and that fault should be used for AS->RMS interactions then the text you cite is ok but I still think your (1) isn't an issue for the spec.  If the fault isn't necessarily mandated in the AS->RMS interactions then I think that line should be changed.  I'm currently leaning towards saying it just applies to the RMD but if the RMS wanted to use it too then that's its own choice but I don't think we can use "MUST" in those cases since its not dealing with RMS->RMD interactions.

If your (1) was related to whether or not an RMS passes a MsgNumRollover fault that it received from the RMD back up to the AS (so it is in essence generating a MsgNumRollover fault on behalf of the RMD) then again this is an impl detail.  The RMS may choose to never expose this fault to the AS - we can't say.

No, this is not my interpretation; I am just trying to apply what the spec text says as it relates to the construction of the state tables.  To support the behavior as stated in the paragraph cited above, I assumed the need for this event (at either RMD or RMS) required some sort of state change that would permit the retransmission of unacknowledged messages while preventing the acceptance of new messages for transmission.  This is the only difference between the connected and the rollover state.  If this state is omitted, then the RMS would continue to fire new messages at the RMD.  The state is there since this behavior is sort of implied by the last sentence of that paragraph.

For (2) - why do you assume that the RMS should close or terminate the sequence?  There are other choices - like start a new sequence for that msg.

That would not be prohibited on a new Sequence; but the old sequence is not useful for the transfer of any new messages.  I guess that there is always either expiry or the RMS’s knowledge that all transferred messages have been acknowledged.  I added the closure option since the spec says in sec 3.2 that either the RMS or RMD MAY close a sequence before terminating it.  Terminating the sequence would be the humane thing to do once all messages have been acked or closure then termination otherwise.  I would hate to leave a rolled over sequence languishing and suffering in the RMD.
True, no more, higher numbered, messages can be transfered but lowered ones can be - that's why I'm not comfortable saying that the sequence should be closed or terminated - it depends on what's going on.  If there are no gaps in the sequence then it probably would be closed or terminated but the RMS may also choose to wait until a rollover sequence is created - we just don't know.  Either way, since the original sequence is still valid (just full) there is no reason to manadate anything happen to it.



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