I’m in favor of the features header
in combination with the version indicator, but the features (capabilities) should
always be negotiated during session setup. For each capability, the lowest “level”
wins. So if A sets up a connection with B and requests “Multiple
attachments=Yes” then B could say “Multiple attachments=No”.
The result will then be “Multiple attachments=No”.
Also, the mininum AS2 protocol version
supported should be 1.0. All the AS2 implementions should be backwards
compatible. Detecting an older version then the one that will support feature
negotiation always means that there are no features to be negotiated.
That way it’s very flexible. This is
how it’s done in other major protocols as well (for example OFTP).
Best,
Gijsbert in ‘t Veld
Covast CTO
From:
owner-ietf-ediint@xxxxxxxxxxxx [mailto:owner-ietf-ediint@xxxxxxxxxxxx] On Behalf Of Kyle Meadors
Sent: Thursday, December 15, 2005
11:21 PM
To: ietf-ediint@xxxxxxx
Subject: RE: profiles in AS2
Not a lot of comments on this thread. But
to summarize…
3 in favor of Option 2 (Features header)
and use of AS2–Version 1.2
1 in favor Option 3 where filtering is
done on a message
Still does not fully address the initial
start–up conditions as Richard pointed out, but perhaps that just can not
be done without some manual setup.
Since this EDIINT WG will likely be
closing relatively soon, I hope we can get some more to weigh in on this. Do
others object to Option 2 (with AS2–Version 1.2)?
For those AS2 vendors supporting Option 2, would this impact your product,
including those deployed in existing supply chains? Are their significant
backward compatibility problems with this choice?
From: Tim McCarthy
[mailto:TMcCarthy@xxxxxxxxxxxxx]
Sent: Wednesday, December 07, 2005
9:14 AM
To: Kyle Meadors;
ietf-ediint@xxxxxxx
Subject: RE: profiles in AS2
Seems to me that a combination of features
2 and 4 would provide everything we’d need.
From:
owner-ietf-ediint@xxxxxxxxxxxx [mailto:owner-ietf-ediint@xxxxxxxxxxxx] On Behalf Of Richard Bigelow
Sent: Tuesday, December 06, 2005
5:07 PM
To: Kyle Meadors;
ietf-ediint@xxxxxxx
Subject: RE: profiles in AS2
These are my comments. Option 2 is
preferred. This memo essentially supports John Duker's memo of Dec. 5,
Features Profile in AS2.
1. This option requires that implementers
of feature 1.n also implement all earlier features. Is that
reasonable? What if 1.5 is difficult and many vendors don't want to do
it, but many want to support 1.6? Not recommended.
2. The features header allows the
partner A receiving the message to know the other partner's (B's)
capabilities. So when A sends to B, A knows what is allowed. A can
also check B's AS2-version; 1.1 does not allow any of the controlled features,
but does allow compression. A should update some state for every message
received from B. B might stop supporting some feature. Recommended.
A possible variant of (2) is that a
partner could send some message to all its trading partners when its
capabilities change. This message would have headers only, no
content. It might be useful to send this capabilities message to partners
that would rarely receive normal messages.
3. This option allows receivers to ignore
messages they don't understand, and to detect those messages without looking
for unknown headers. But it does not provide a mechanism for the sender
to know whether a receiver can receive the message. Suppose we had done
compression this way. A could send a compressed file to B, and B could
ignore it based on the feature header, but then the file is lost. B could
return a new MDN code indicating unsupported-feature, and A could then send the
uncompressed file, in this example. In other cases, A would have to use
some other mechanism. A could remember that B rejected the file and not
try that feature again, but how would A know if B upgraded and can now support
the feature? The original intent of the features header was that the
sender could know in advance if the receiver supports the feature. 3 is
not recommended.
4. Before sending a message to B, A should
ask B for B's capabilities, and check if B supports the feature. Since B
might stop supporting a feature, A should ask each time. This is ok for
rare messages, like CEM, but not for common ones, like Multiple Attachments.
Not recommended.
None of these protocols fully addresses
the initial case. Before any messages are exchanged, how do the partners
know each other's capabilities? Each partner must assume that the other
supports only the basic 1.0 AS2 protocol. Hopefully, they will be
able to exchange normal messages, which will contain at least the 1.2 version
header. They can then use option 2 to discover each other
capabilities. This probably works for most features. For CEM, either
they must first exchange test messages that are unencrypted and unsigned to
establish CEM capability, or exchange initial certificates manually.
Alternatively, the partners would
configure each other manually the first time. Thereafter, they would be
automatically updated on each other's capabilities.
From:
owner-ietf-ediint@xxxxxxxxxxxx [mailto:owner-ietf-ediint@xxxxxxxxxxxx] On Behalf Of Kyle Meadors
Sent: Thursday, December 01, 2005
9:04 AM
To: ietf-ediint@xxxxxxx
Subject: profiles in AS2
I am needing the opinion of the AS2 community on the use of
a feature profiles within AS2. Back in 2002, compression was added as an extra
feature. Using "AS2–Version: 1.1" in a message indicated the UA
could support compression even if the actual message did not contain the
compressed envelope. This assisted implementers in knowing if their trading
partners could support compression.
Moving
to the present, users are requesting new features. These include I–Ds for
Reliability (from GS1), Multiple–Attachments (oil & gas users) and
Certificate Exchange Messaging (Wal–mart, P&G and others GS1
companies). Given AS2's adoption, I am sure there will be others in the future.
My
question to those on this elist is how to do move forward with new features.
What do we do to insure only those who support a feature receive it (e.g., only
sending CEM message to trading partners who support that profile)? Also, can
anything be done to insure backward compatibility to keep new Feature Header
messages from being sent to & breaking older, existing implementations
(e.g. older implementation errors gracefully when getting an unrecognized MA
message).
Here
are some options. I would like to hear your thoughts on what is best or other
ideas.
1. Use AS2–Version header to indicate UA support of
profiles (e.g. 1.2 indicates CEM, 1.3 indicates CEM, Reliability). Works like
compression (e.g. “1.2” indicates capability of CEM but not an
actual CEM message).
2. Use a new header, e.g. EDIINT–Features. The
features header shows all features supported by UA (e.g. EDIINT–Features:
CEM, multiple–attachment) but like AS2–Version does not indicate
every message contains profile.
3. Use a new header for each feature which is present ONLY
in the message using that feature. For example, “CEM–Profile”
for CEM messages. This could allow receiving UA to filter in only profiles it
recognizes.
4. Create a “Capability Query” AS2 Message which returns a
Capability MDN. MDN indicates what features receiving UA can support.
Kyle Meadors
Principal, Test Process
Drummond Group Inc.
615.212.0826
