RE: T2, Proposed solution for ... Re: SyncReply andReliableMessagingMethod in QualityOfServiceInfo

[David Fischer <david@drummondgroup.com>]

Arvola,

Yes, the From Party MSH will retry if it does not receive a DeliveryReceipt.
The IM MSH will retry if it does not receive an Ack (or the From to the first
IM...).

No, we don't need another set of Retry/RetryInterval parameters.  There is a CPA
(or something like it) between the From and To Party's.  This set of parameters
already handles end-to-end.  There is an different CPA (or something like it)
between the From and the next IM (and also between each pair of IMs forming a
Hop).  The Retry/RetryInterval parameters in the IM CPA already cover that hop.

The only problem with all this is making sure the RetryInterval to the end is
longer than the RetryInterval to the first IM.  Some implementations w/o CPPA
may have only one Retry/RetryInterval setting for everything which might pose a
problem.  I think this is an implementation detail that will take care of itself
and we don't need to delve into it (out of scope).

I still disagree with sending a DeliveryReceipt Reliably (someone made this
suggestion?).  This is going overboard.  Effectively, DeliveryReceipt is the Ack
for end-to-end Reliable Messaging.  We shouldn't request Acks on Acks.  If it
doesn't get there, the sender will retry and any problems will be obvious.
OTOH, Business Process/Application Level Delivery Receipts SHOULD be sent
Reliably, but that is out of our scope (we probably picked a bad name for
end-to-end Acks -- too much confusion).

Regards,

David Fischer

-----Original Message-----
From: Arvola Chan [mailto:arvola@tibco.com]
Sent: Friday, August 24, 2001 8:14 PM
To: Burdett David; 'David Fischer'
Cc: ebXML Msg
Subject: Re: T2, Proposed solution for ... Re: SyncReply and
ReliableMessagingMethod in QualityOfServiceInfo


David and David:

Are you saying that a sending MSH must retry either if an intermediate
Ack has not been received or if the end-to-end DeliveryReceipt has not
been received, and that the resent message should carry an incremented
retry count if it is being resent due to non-receipt of the end-to-end
DeliveryReceipt?

If so, do we need two sets of retry parameters (i.e., retry count and
retry interval) to govern the two different kinds of retry?

Thanks,
-Arvola

-----Original Message-----
From: Burdett, David <david.burdett@commerceone.com>
To: 'David Fischer' <david@drummondgroup.com>; Arvola Chan
<arvola@tibco.com>
Cc: ebXML Msg <ebxml-msg@lists.oasis-open.org>
Date: Friday, August 24, 2001 5:46 PM
Subject: RE: T2, Proposed solution for ... Re: SyncReply and
ReliableMessagingMethod in QualityOfServiceInfo


>David
>
>I largely agree with you specifically see below marked with <db></db>
>
>David
>
>
>-----Original Message-----
>From: David Fischer [mailto:david@drummondgroup.com]
>Sent: Thursday, August 16, 2001 4:14 PM
>To: Arvola Chan
>Cc: ebXML Msg
>Subject: RE: T2, Proposed solution for ... Re: SyncReply and
>ReliableMessagingMethod in QualityOfServiceInfo
>
>
>Arvola,
>
><df> comments inline </df>
>
>David Fischer
>Drummond Group.
>-----Original Message-----
>From: Arvola Chan [mailto:arvola@tibco.com]
>Sent: Tuesday, August 14, 2001 10:35 AM
>To: HUGHESJIM (HP-Cupertinoex1); ebXML Messaging (E-mail)
>Subject: Re: T2, Proposed solution for ... Re: SyncReply and
>ReliableMessagingMethod in QualityOfServiceInfo
>
>
>My opinion is that the current spec is so broken that extensive
>changes may be necessary to get end to end reliable messaging
>over multiple hops to work properly. I agree with you and that
>intermediate Acks used by the intermediaries are the likely source
>of the problem.
><df> agreed </df>
>
>If we stipulate that only the sending MSH and the receiving MSH
>adopt the reliable messaging behavior, I believe end to end reliable
>messaging will work regardless of whether intermediaries are
>present. However, this may make reliable messaging not very
>useful for certain use cases, e.g., where the sending MSH does
>not have a permanent Internet presence.
>
><df>  This is not all that hard if we keep the present structure of
>DeliveryReceipt as the end-to-end Ack and the Acknowledgement element as
the
>IM
>hop Ack.
><db>Agreed</db>
>This is already in the spec and nothing about these elements needs to
>be changed.  We only need to specify in section 10 that if the To Party MSH
>gets
>a DeliverySemantics=1&o1 then send a DeliveryReceipt to the From Party MSH
>(along with ...).
><db>I think I agree.</db>
>
>Unfortunately, this does not deal with the duplicate problem.  If I (the
>From
>Party MSH) don't get a DR back, then I will retry (Retries and
RetryInterval
>are
>end-to-end parameters, not hop-to-hop).  I don't want any IMs rejecting my
>retry
>due to duplicates.  We can fix this by either:
> 1) telling the IMs not to worry about duplicates or
> 2) add a RetryCount attribute and change the way
> IMs handle duplicates.
><db>I think that a Retry Count is the best way to go handle this rather
than
>a different MessageId that I suggested earlier.</db>
>
>The way we handle duplicates now is definitely broke.  </df>
>
>I now realize there is a problem in my previous proposal to have
>the sending MSH stop retrying once it gets an Ack from the next
>intermediary, and then wait for the DeliveryReceipt from the
>receiving MSH. Unless the DeliveryReceipt is sent reliably, it
>may get lost, so the sending MSH may falsely notify the sending
>application that reliable messaging has failed.
><db>Yes and no. If the DR is being sent asynchronously on a spearate
session
>then it needs to be sent reliably. If it is being sent synchronously on the
>same channel then the DR is the acknowledgement and so does not need to be
>sent reliably.</db>
>
>If the DeliveryReceipt
>is sent reliably, then it may require end to end acknowledgement
>from the sending MSH, possibly triggering an infinite chain of
>DeliveryReceipt messages. (A possible workaround may be to
>require that if a DeliveryReceipt is sent reliably and on its own,
>then it must not request for DeliveryReceipt.)
>
><df> agreed -- no DR for a DR and no Ack for an Ack and no Error on an
>Error.
><db>Completely agree</db>
>We can get carried away with RM if we start sending Acknowledgements or DR
>reliably.  We also have to pick either Ack on Error or Error on Ack but not
>both.  I think I prefer Error on Ack... I'm not sure?
><db>This depends on whether the original message was being sent
>synchronously for the same reasons as in the Delivery Receipt discussion
>above.</db>
></df>
>
>-Arvola
>
>-----Original Message-----
>From: HUGHES,JIM (HP-Cupertino,ex1) <jim_hughes@hp.com>
>To: ebXML Messaging (E-mail) <ebxml-msg@lists.oasis-open.org>
>Date: Monday, August 13, 2001 7:17 PM
>Subject: RE: T2, Proposed solution for ... Re: SyncReply and ReliableMessa
>gingMethod in QualityOfServiceInfo
>
>
>>Question: Does "reliable messaging" mean that the initial MSH (and maybe
>>intermediate node MSHs) needs to consider this as a quality request and,
if
>>possible, pick the "most" reliable transport available? Or, is this just a
>>protocol for the receiving MSH to send a confirming ACK back to the
sending
>>MSH?
>>
>>I think it's the latter, and thus there is no directive for intermediate
>>node links to use the RM protocol to confirm among themselves that this
>>message got through. From their perspective, the overall MSH Ack looks
like
>>a higher level function to them... and, in fact, it seems to me that
having
>>the intermediate links try to use their own version of RM between their
>>endpoints really complicates the picture and maybe they should be
>prohibited
>>from trying to use RM since they aren't the start/end-points for the
>overall
>>message... IMO.
>>
>>jim
>>
>>
>>
>>> -----Original Message-----
>>> From: Arvola Chan [mailto:arvola@tibco.com]
>>> Sent: Sunday, August 12, 2001 9:30 PM
>>> To: David Fischer; Burdett David
>>> Cc: ebXML Messaging (E-mail)
>>> Subject: Re: T2, Proposed solution for ... Re: SyncReply and
>>> ReliableMessaging Method in QualityOfServiceInfo
>>>
>>>
>>> David:
>>>
>>> My comments are bracketed by <ac> and </ac>.
>>>
>>> Cheers,
>>> -Arvola
>>>
>>> ----- Original Message -----
>>> From: "David Fischer" <david@drummondgroup.com>
>>> To: "Arvola Chan" <arvola@tibco.com>; "Burdett David"
>>> <david.burdett@commerceone.com>
>>> Cc: "ebXML Messaging (E-mail)" <ebxml-msg@lists.oasis-open.org>
>>> Sent: Sunday, August 12, 2001 2:33 PM
>>> Subject: RE: T2, Proposed solution for ... Re: SyncReply and
>>> ReliableMessaging Method in QualityOfServiceInfo
>>>
>>>
>>> > Arvola,
>>> >
>>> > What if I am sending to you and you are using an IM for
>>> some reason, e.g.
>>> no
>>> > persistent connection?  I might not even know and since I have no
>>> agreement with
>>> > that IM (my agreement is only with you), I cannot be responsible for
>>> putting the
>>> > CPAid in the Via -- there is no CPAid.  What I can do is
>>> fill in the Via
>>> fields
>>> > as much as I am able in case there is an IM I am not aware
>>> of.  This, IMO
>>> will
>>> > be a very common use case.
>>> >
>>> > This exact same situation would arise if you used multiple
>>> MSHs where one
>>> was a
>>> > mailroom.
>>> >
>>>
>>> <ac>
>>> I must admit that your use case is a very valid one and I
>>> have not made
>>> provision for
>>> it.
>>>
>>> Come to think of it, when I suggested that the sender MSH
>>> should dictate if
>>> all intermediaries
>>> should use reliable message or not at all, it is not strictly
>>> necessary for
>>> the sender MSH to
>>> know that intermediaries are involved, all it is choosing is between
>>> reliable message with
>>> intermediate Acks vs reliable messaging without intermediate Acks.
>>>
>>> As you have indicated earlier, "Even though the ends don't
>>> need to know
>>> about the IMs,
>>>  it is critical that the IMs realize their role." There, the
>>> IMs should be
>>> able to respect the
>>> directive from the sender MSH to use intermediate Acks or not.
>>> </ac>
>>>
>>> > You are correct, I need to be more clear.  I believe the
>>> sender MSH would
>>> > construct the Via.  This Via would pass to the first IM MSH
>>> who would
>>> construct
>>> > a new Via (possibly very similar to the original) and pass
>>> this new Via to
>>> the
>>> > next hop's MSH.
>>> >
>>> > NEW PROBLEM WITH MULTI-HOP?
>>> > This brings up a good point.  I (the From Party MSH) know
>>> how to send to
>>> you
>>> > (the To Party MSH) because I can look up your connection
>>> info in the CPA
>>> > Database based upon a CPAid and a ChannelID.  This info
>>> might not reside
>>> in the
>>> > To PartyID element.  If my message goes through an IM, how
>>> does the IM
>>> know
>>> > where to send?  I don't send to you, I send to my IM.  If I
>>> am using an
>>> IM, does
>>> > that mean any time I make an entry in my database I also
>>> have to duplicate
>>> that
>>> > info to my IM (and they to each of their IMs etc.)?  This
>>> would not be
>>> > acceptable.  Maybe this connection info MUST reside in the
>>> To PartyID?
>>> This
>>> > would not be a problem for single-hop.  Maybe the Receiver
>>> connection info
>>> needs
>>> > to be put in the Via?
>>> >
>>>
>>> <ac>
>>> I agree with you this is a problem. The intermediary needs to
>>> be configured
>>> with the
>>> Endpoint and various characteristics for the To Party (or the
>>> Endpoint for
>>> yet another
>>> intermediary who can route messages to the To Party directly
>>> or indirectly
>>> and its
>>> characteristics). My understanding is that CPPs and CPAs
>>> currently deal only
>>> with
>>> the point to point case. Therefore, there is no automated way
>>> to configure
>>> intermediaries
>>> using CPAs. This is something the CPP/A TC will have to
>>> address in its 2.0
>>> spec.
>>> </ac>
>>>
>>> > Regards,
>>> >
>>> > David Fischer
>>> > Drummond Group.
>>> >
>>
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