HI,
The terms “retry” and “resend”
are used in different ways in this Internet-Draft, and are not synonymous.
The idea is that a resend is sending the
message again after it was apparently successfully sent.
The resend operation only really makes
sense in the context of “asynchronous” MDNs where you are waiting
for a MDN and think the MDN may have gotten dropped on the floor, was not
created, or otherwise failed somehow, because no MDN has arrived _when_ you were expecting one.
[The term “retry” is used when
the message is not known to have been sent (no 200 OK, the connection was refused,
503 server busy, and so forth).
You can think of it as if the resend
timers only start when waiting for a MDN. If no MDN is requested, you are
expected to not be waiting for one. In other words, the operation of resending
never even starts unless a MDN had been requested, so there is no reason to say
what would stop it in the case, “no MDN requested.”
[In addition, the operation of resend never
starts when a synchronous MDN is requested. In that case, you can only retry if
you don’t get the MDN in the HTTP reply. Of course, you don’t retry
if you get the MDN and a 200 OK. One case we did not consider, come to think of
it, is requesting a synchronous MDN, getting a 200 OK, but no MDN! Should we
retry that one?]
Thanks for your comment and we will try to
make it more clearly evident that resend operations are very different from
retry operations.
From: Shan Harter
[mailto:Shan <at> systrends.com]
Sent: Monday, August 15, 2005 11:41
AM
To: duker.jp <at> pg.com;
ietf-ediint <at> imc.org
Cc: Dale Moberg
Subject: RE: AS2 Reliability Draft
for "Once and Only Once" Delivery
We really don't want to keep retrying if
receiving party did receive AS2 message but NO MDN is required:
"message, with the same content and
the same Message-ID value is sent
again. This operation is referred to as a resend of the message. This
document will suggest guidelines to prevent AS2 software
implementations that receive duplicate messages from distributing
that message to back-end business applications, as well as guidelines
on resend intervals and resend counts for various modes of AS2
operation. Resending ends when the MDN is received", when a HTTP 200 OK is received when NO MDN is requested, "or the resend
count is reached."
-----Original Message-----
From: owner-ietf-ediint <at> mail.imc.org
[mailto:owner-ietf-ediint <at> mail.imc.org]
On Behalf Of duker.jp <at> pg.com
Sent: Monday, August 15, 2005 7:45
AM
To: ietf-ediint <at> imc.org
Cc: dmoberg <at> cyclonecommerce.com
Subject: AS2 Reliability Draft for
"Once and Only Once" Delivery
A new Internet Draft addressing reliable delivery of
AS2 messages is available at:
http://www.ietf.org/internet-drafts/draft-duker-as2-reliability-00.txt
for review and discussion.
The
purpose of the draft is to define ways to ensure that AS2 messages are
delivered "once and only once". One key aspect is to ensure that AS2
implementations do not pass "Duplicate Messages" on to back-end
business applications. The ultimate goal is to gain agreement on standard
approaches so that all AS2 software implementations can deliver this
functionality. We look forward to comments and suggestions from all interested
parties.
John
Duker Dale Moberg
Procter
& Gamble Cyclone Commerce
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