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RE: profiles in AS2
I will also chime in in favor of Kyle's original option
2.
However, I will disagree with John's latest point (a). Well
behaved software should ignore any headers it does not understand or support.
Therefore, I see no problem with a 1.2 (or greater) version system always
sending the EDIINT-Features header.
John Koehring
Cyclone Commerce, Inc.
I agree that a 1.1 version should
accept messages from a 1.2 version. I think that it is the responsibility
of the 1.2 (or greater) version to recognize that it is communicating with a
lower (1.0 or 1.1) version and
(a) not
send the Features Header to either, and
(b) not use compression with the 1.0 version.
So versions greater than 1.1 will need to check the
version values for every message, and if the version received is greater than
1.1, the receiver should check for a Features Header. The receiver should update
state information contained in the Version Header and Features Header for that
partner (if the state info changed).
John Duker
Procter &
Gamble
|
| "Richard Bigelow"
<richard.bigelow@xxxxxxxxxx>
Sent by: owner-ietf-ediint@xxxxxxxxxxxx
12/19/2005 01:56 PM
|
To:
"Dale Moberg" <dmoberg@xxxxxxxxxxxxxxxxxxx>, "Kyle
Meadors" <kyle@xxxxxxxxxxxxxxxxx>,
<ietf-ediint@xxxxxxx>
cc:
Subject:
RE: profiles in AS2 |
Concerning a 1.2 version interoperating with a 1.1 version:
The 1.1 version should accept the 1.2 messages. The compression
draft says that a version of 1.1 or greater indicates compression.
I have some concern about Kyle's comment that this WG may
be closing soon. Is this in response to IETF's requirement to make
progress on AS3? I hope that this WG will continue. We have some
proposals on the table, including Reliability and CEM and perhaps Profiles in
the future.
Richard Bigelow
Inovis
richard.bigelow@xxxxxxxxxx
From: owner-ietf-ediint@xxxxxxxxxxxx
[mailto:owner-ietf-ediint@xxxxxxxxxxxx] On Behalf Of Dale
Moberg
Sent: Saturday, December 17, 2005 7:49 AM
To: Kyle
Meadors; ietf-ediint@xxxxxxx
Subject: RE: profiles in AS2
The consensus seems to be that it should be possible to
support some AS2 features independently, rather than cumulatively. Although I
think the combinations of features of Reliability, CEM, and Multipart could be
coded up by 8 numbers, if more end user requirements get specified, that
encoding would become inconvenient to support. So moving to an EDIINT-Features
header seems to be a reasonable way to advertise capabilities.
Would AS1, AS2 and AS3 all use this header? I assume that CEM and
attachments are OK, but Reliability mainly pertains to AS2. Also, would AS1 have
to add an "X-" preface to the header? (So we would have somemething like
"X-EdiintFeatures" as the header value?)
I
take it that there is some concern about the waste of sending this header every
time and that partially motivates inventing new behavior to supply these values
in a MDN (when requested). While that might be more elegant, I guess the logic
would be that you can only use that form of request when the original has an
AS2-Version of "1.2"? My preference here is not to try to develop option 4 into
a new capability query and response pattern, but just accept that the
Ediint-Features header may waste a few bytes per message.
How will existing applications respond to this? Presumably they would (or
should) ignore an included "EdiintFeatures" header and also never send one. If
they never sent one (and their ASx-version was either 1.0 or 1.1), then they
must not be sent multiparts or CEM. In that case, messages with the new features
would not even be sent to older applications and could not cause them to
malfunction. So it should be stated that you may not use these features unless
the other side both has a version value greater than 1.1 and also has included
the feature in its EdiintFeatures header.
What should be said about a 1.2 version interoperating with a 1.1
version? Since a 1.1 level app. would be entitled to ignore a message with a
higher version, should a 1.2 app be advised to be configurable to advertise
itself as a 1.1 version to promote interoperation?
What should be done about detecting a change (upgrade) of versions when
the other side begins sending the higher "1.2" value? Are implementations
expected to check the version or is this left to the implementation? Richard B.
says "A should update some state for every message received from B" I think it
would be sufficient to check the state and update if a change is noticed. (Maybe
that is what Richard meant though.) I suppose an empty message could be sent to
announce a change in capabilities, but again only to ediint agents with a
version greater than 1.1.
So far the
specifications have not really required that the version be checked for every
message. For example, the AS3 draft says
The AS3-Version header is a header which
is required only if the value
of the header is not "1.0". Its purpose is to allow systems to
determine which version
of this specification, should the
specification evolve over time, the sender of a document
has used to
package the
document. A user agent MUST NOT reject a message if the
version header is missing.
AS3-Version: 1*DIGIT . 1*DIGIT
A version header value of "1.1" indicates an implementation
can
support EDIINT data
compression [18]. A user agent MUST NOT send
compressed messages to trading partners who do not use a
version
header of "1.1"
or greater.
It seems to me that versions greater than 1.1 will need to check the
version values for every message. If a version header is missing, it is version
1.0.
From: owner-ietf-ediint@xxxxxxxxxxxx
[mailto:owner-ietf-ediint@xxxxxxxxxxxx] On Behalf Of Kyle
Meadors
Sent: Thursday, December 15, 2005 3:21 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?
Kyle Meadors
DGI
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.
Richard
Bigelow
Inovis
richard.bigelow@xxxxxxxxxx
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
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