Comments on Issue 66

[Tom Rutt <tom@coastin.com>]

Description from Issue 66 states:
"
            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
"

The ws-rm spec wording implies that there is a difference in behaviour 
(as described in the Hitachi proposed state tables) between
the RMD in states "closed" and "lastReceived".
   The RMD continues to "deliver" retransmitted messages with msgNo less 
than the last messageId value, when in the last state.
   The RMD does not deliver any messages when in the closed state.

This difference in behaviour is significant.  Last is used for orderly 
shutdown (with no lost messages at time of sequence terminiation).

Tom Rutt
.

-- 
The key issue here is 

----------------------------------------------------
Tom Rutt	email: tom@coastin.com; trutt@us.fujitsu.com
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