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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 From:
owner-ietf-ediint@xxxxxxxxxxxx [mailto:owner-ietf-ediint@xxxxxxxxxxxx] On Behalf Of Dale Moberg 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: 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] Seems to me that a combination of features
2 and 4 would provide everything we’d need. From: 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 From: 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. 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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