Re: Implementation question for RM spec!

[christopher ferris <chris.ferris@east.sun.com>]

Jim/All,

It isn't clear to me why it would be necessary to
block until the previously sent message is ack'ed.
That would be one manner of implementing, but not an
approach I'd choose. 

Since each message is ack'ed individually, you can
send as many messages as you like and process the
acks or retry (in the case of a timeout) oob.

The specification stipulates that one MAY use either
the sequence number OR the messageId (refToMessageId)
for the purposes of determining which message is being
ack'ed.

This is my understanding of what we have worked out for
phase one. Possibly, it is misguided, but I for one would
not advocate a (logically) blocking protocol.

Cheers,

Chris

Jim Hughes wrote:
> 
> Sanjay,
> 
> Reliable Message grouping (sending one ACK for a group of messages) was
> eliminated in phase 1 for a variety of reasons - error propagation not well
> understood, how to handle partially sent groups, how to recover, etc. The
> result is a very simple solution that does enforce a single pipeline as you
> point out, with each reliable message being acknowledged before the next
> one is sent (unreliable messages flow at any time). We will remove the
> restriction after Phase 1, when there will be more normative specifications
> for implementors. Simplicity rules for the moment...
> 
> Jim Hughes
> Fujitsu
> 
> At 06:56 PM 9/29/2000 -0700, Patil, Sanjay wrote:
> 
> >Jim,
> >
> >Could you please also comment on the third question in my original mail.
> >It's about parallelism between any given sender-receiver pair.
> >Is this restriction of working on one message at a time between
> >any given sender-receiver pair a result of some TRP
> >decision to get rid of the windowing. I vaguely remember
> >your initial RM spec talking about windowing.
> >
> >Please advise.
> >
> >thanks,
> >Sanjay Patil
> >----------------------------------------------------------------------------
> >------------------------------
> >Work Phone: 408 350 9619
> >http://www.netfish.com
> >
> >
> >-----Original Message-----
> >From: Jim Hughes [mailto:jfh@fs.fujitsu.com]
> >Sent: Friday, September 29, 2000 6:37 PM
> >To: ebxml-transport@lists.ebxml.org
> >Subject: Re: Implementation question for RM spec!
> >
> >
> >Marty's exactly right on the complexity issues.
> >
> >The current TRP resolution for RM requires each sending MSH to generate
> >sequence numbers for each sender-receiver pair (regardless of transport).
> >Whether a receiving MSH actually uses the sequence number or the globally
> >unique MessageID to detect duplications is implementation dependent. It's a
> >lot easier to detect dups using sequence numbers...
> >
> >Jim
> >
> >At 06:10 PM 9/27/2000 -0400, Martin W Sachs/Watson/IBM wrote:
> >
> > >I believe that you correctly understand the intent of the RM protocol and
> > >its implementation requirements.  There indeed has to be a separate
> > >"logical channel" for each pair of channels, if not for each conversation,
> > >using reliable messaging, precisely to avoid the  blocking you mention.
> > >That's what it takes to get the parallelism you mention.
> > >
> > >I believe that the implementation would be simplified and perform better if
> > >the sequence numbers were eliminated as someone (yourself?) has already
> > >suggested.  I assume that sequence numbers have been discussed at this
> > >week's TRP face to face.
> > >
> > >Except for the sequence number question, I believe that exactly the same
> > >implementation considerations would be present if reliable messaging were
> > >done in the transport layer instead of the message service.
> > >
> > >Regards,
> > >Marty
> > >***************************************************************************
> >**********
> > >
> > >Martin W. Sachs
> > >IBM T. J. Watson Research Center
> > >P. O. B. 704
> > >Yorktown Hts, NY 10598
> > >914-784-7287;  IBM tie line 863-7287
> > >Notes address:  Martin W Sachs/Watson/IBM
> > >Internet address:  mwsachs @ us.ibm.com
> > >***************************************************************************
> >**********
> > >
> > >
> > >
> > >"Patil, Sanjay" <Spatil@netfish.com> on 09/27/2000 02:45:15 PM
> > >
> > >To:   "Ebxml-Transport (E-mail)" <ebxml-transport@lists.ebxml.org>
> > >cc:   "Ebxml-Poc (E-mail)" <ebxml-poc@lists.ebxml.org>, "Askary, Sid"
> > >       <saskary@netfish.com>
> > >Subject:  Implementation question for RM spec!
> > >
> > >
> > >
> > >
> > >
> > >I was going through the Reliable Messaging spec for scoping the work
> > >involved in implementing the spec for the upcoming Tokyo POC.
> > >Questions about the same ...particularly in the context of the following
> > >requirement posed by the RM spec ...
> > >      A sender MSH should not send the next message till it receives
> > >      an Acknowledgement Message from the Receiver.
> > >
> > >   1>This will necessitate instantiating a separate MSH instance for each
> > >recipient
> > >      party, as it will not be fair for blocking outgoing messages to
> > >Parties
> > >having
> > >      a clear messaging channel while Messages to Parties with poor links
> > >are
> > >
> > >      successfully sent (tried to send).
> > >
> > >   2>This will also mean that separate outbound message queues are to be
> > >      maintained for each recipient. For each recipient Party, I will have
> > >to
> > >manage
> > >      the lifecycle of a dedicated SequenceCounter i.e.recycling the
> > >SequenceCounter
> > >      upon tripping over the max as well as when they get stale after "long
> > >time".
> > >      In hub scenarios, this will amount to a lot of runtime objects
> > >creation
> > >and
> > >      will also require an ongoing activity in the server to manage the
> > >queues and
> > >      lifecycles of the SequenceCounter objects.
> > >
> > >   3>With lots of outbound messages for the same recipient Party, there
> > >      should be some provision for parallelism. Typically when servers can
> > >handle multiples
> > >      of parallel message exchanges, the RM spec will necessitate using a
> > >single
> > >      pipeline resulting into underutilization of capacity and slowing down
> > >of the entire
> > >      process. Critical messages requiring immediate transfer might get
> > >stuck
> > >in the
> > >      queue for unreasonable amount of time.
> > >
> > >Or am I missing something very fundamental. It's been a while I have done
> > >ebXML,
> > >and with the Tokyo POC not very far, I got to catch up :-).
> > >
> > >thanks,
> > >Sanjay Patil
> > >---------------------------------------------------------------------------
> >-
> > >
> > >------------------------------
> > >Work Phone: 408 350 9619
> > >http://www.netfish.com