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EDIINT Working Group                                              Chuck Shih
draft-ietf-ediint-as2-05.txt                                      Dale Moberg
Expires in six months                                             Rik Drummond
                                                                  Dick Brooks
                                                                  20 July 1999

                      HTTP Transport for Secure EDI

<Updates

x  Add section describing use of multipart/form-data for EDI transport
   one GISB and E5 fundamental alignment addition.
x  Add references to the RFCs, GISB, W3C that are needed
x  Only one sentence so far-- add section on 'authentication'
   (authorization to use resource-- denial of service deterrent)
   by mentioning how it is done  in [HTTP]. No specification of
    basic as preferred, so support 'em all.
x  Add support  for aysnchronous MDN indication, see Receipt-delivery-option
x  Add metadata jargon to get a higher abstraction level to help
    in discussing headers vs form-data implementations
x  Add generalized receipt section on multipart/report with more open machine-readable section,
    same approach to signing and inclusion of Hash value of original data.
x Resolve FROM overloading issue by permitting new receipt styles
   and adding some new headers to fulfill needed functional roles
   for sender id values that are not email addresses.
x  The names and value ranges used in the multipart/form-data--
    followed the lone submission.
x  The format of the returned messages in the human and
    machine readable parts. Semantics left very open for
    the machine readable parts of the 'generalized' receipt.
? New metadata and return fields -- do we have
   all these now Dick GISB E5 folks ? The name parameters within
    the Content-Disposition headers of multipart/form-data body parts
    should support the alignment of AS2 with GISB and E5.
? Removed all modality words and other language that might
    suggest we were respecifying the already specified- OK now?

/Updates>

Status of this Memo

This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.

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months and may be updated, replaced, or obsoleted by other
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Abstract

This document describes how to exchange EDI documents securely
using http transport for EDI data that is packaged in MIME messages
that use public key security body parts.

Feedback Instructions:

If you want to provide feedback on this draft, follow these guidelines:

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   section in question.

Table of Contents

1.  Introduction
   1.1 Purpose and relation to previous work
   1.2 Overall operation
2. Stages and Details of  HTTP EDI Transmission and Acknowledgment
    2.1   Requesting receipts in the POSTED request
    2.1.1   Requesting MDN-based receipts
    2.1.2   Requesting Generalized receipts
    2.1.3   Summary of Receipt request options
    2. 2  Sending EDI in HTTP POST Requests
    2 .3  Using Transport Layer Security for Transmission
    2.4.   Response Status Codes in Replies
    2 .5   Receipt Reply
    2.5.1  MDN based Receipts and Signed MDN Receipts
    2.5.2  Generalized Receipts and Signed Receipts
    2.6   Additional Reply Content
    2.7  Non-Repudiation of the POST Reply
    2 .8  Error Recovery
 3. Referenced RFCs and their contribution
   3.1  RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1 [HTTP]
   3.2  RFC 2246: Transport Layer Security [TLS]
   3.3  RFC 1847: MIME Security Multiparts [SECURITY]
   3.4  RFC 1892: Multipart/report [REPORT]
   3.5  RFC 1767: EDI Content [MIMEEDI]
   3.6  RFC 2015: PGP/MIME [MIMEPGP]
   3.7  RFC 2045, 2046, and 2049: MIME [MIME]
   3.8  RFC 2298: Message Disposition Notification [MDN]
   3.9  RFC 2311: S/MIME Version 2 Specification [SMIMEV2]
   3.10 RFC XXXX: MIME-based Secure EDI [AS1]
   3.11 RFC 2388: Multipart/form-data [FORMDATA]
4. Other differences to notice in HTTP and SMTP based transport
   4.1 Unused MIME headers and operations
    4.1.1  Content-Transfer-Encoding not used
    4.1.2  Epilogue must be empty
    4.1.3  Lengthy message bodies and Message/partial
   4.2 Differences in MIME or other headers or parameters used
    4.2.1  Content-Length needed.
    4.2.2  Final Recipient and Original Recipient
    4.2.3  Message-Id and Original-Message-Id
    4.2.3  Host header
   4.3 New Options for HTTP transport

5.  Acknowledgments

6.  References

7.  Authors' Addresses

A.  Example exchange.

1.  Introduction

    1.1 Purpose and relation to previous work

    Early work on Internet EDI focused on specifying MIME content
    types for EDI data [MIMEEDI] The functional requirements
    document , "Requirements for Interoperable Internet EDI,"
   [EDIINT] provides extensive information on EDI security
    and the business and user processes that can benefit
    from the use of EDI security. In addition, MIME structures
    appropriate for SMTP transport of the packaged EDI data are
    specified in ([AS1] "MIME-based Secure EDI" ) as well
    as details needed to support signed receipts as acknowledgments.
    The framework of [AS1] shows how to implement the security features--
    specifically data privacy, data integrity/authenticity,
    non-repudiation of origin and non-repudiation of receipt --
    found to be requirements for secure EDI.

    In this document, it is assumed that the reader is familiar
    with the SMTP/MIME transport document, the requirements document,
    and the RFCs applied or referenced in those documents.

    This draft, like the SMTP/MIME transport document, builds on
    previous RFCs and is attempting to "re-invent" as little
    as possible.  The goal here is to specify how previously specified
    MIME messaging structures and operations can be adapted for use with
    HTTP servers and clients to obtain secure, reliable,
    and acknowledged transport for EDI data.

    The applicability statement, [AS1] "MIME-based Secure EDI,"
    explained the basic EDI transaction using the concept of a
    "secure transmission loop" for EDI. This loop involves
    one organization sending a signed and encrypted EDI
    interchange to another organization,  requesting a signed receipt,
    followed later by the receiving organization sending this
    signed receipt back to the sending organization. The transmission
    involves the following stages:

       i. The organization sending EDI/EC data encrypts the data and
       provides a digital signature, using either PGP/MIME or S/MIME.
       In addition, they request a signed receipt.

       ii. The receiving organization decrypts the message and verifies
       the signature, resulting in verified integrity of the data and
       authenticity of the sender.

       iii. The receiving organization then sends a signed receipt
       using a signature over the hash of a message disposition
       notification, which contains a hash of the received message.

    The above describes functionality which, when implemented, would
    satisfy all security requirements. Other restricted subsets of
    functionality (for example, only signature and no signed receipt)
    have also been characterized.

    In this document, the goal is to make use of HTTP instead of SMTP
    as a transport protocol, and make changes that are needed to adapt
    to protocol packaging differences.

    In either transport case, the body of the message is a MIME structure,
    using MIME headers ("content-type" and other "content-X" tags)
    to convey information about the data being transported.

    Also, one primary use of SMTP RFC 822 headers within SMTP based transport
    of secure EDI has been to enable requests for acknowledgements and
    to specify options for signatures over acknowledgements (asymmetric
    encryption and cryptographic hash algorithm preferences).

    One way to convey this information within the HTTP transport context is
    to use either HTTP entity-headers or extension-headers
    [11, section 7.1] that have the syntax of  SMTP headers. Only the "From"
    header is overloaded by possibly different usages in the SMTP and HTTP context.
    The From header normally contains machine-usable email addresses
    as defined in [SMTPMSG]. The usage of the FROM header in [HTTP] section 14.22
    is to provide the email address of an administrative contact for the HTTP client.
    The function of the "From" header in the SMTP context of secure EDI transport
    has been to supply a value used in constructingthe MDN style receipt.
    But the MDN receipt has been found to be too restrictive for some commercial
    EDI transport scenarios [GISB]. So alternative receipt mechanisms will be provided
    that, among other things, will remove any conflicts arising from trying to reuse the SMTP-MDN
    roles of  "From"  within the context of HTTP reserved  usage of "FROM".

    Also, it is currently difficult to make use of HTML [HTML] and simple scripting
    to send HTTP entity-headers as part of the HTML FORM tag construct.
    For HTML-based POST situations [GISB], it is useful to specify
    ways to convey 'metadata' needed for the secure transmission loop that
    do not make use of HTTP headers. One way to specify this data is
    by using the MIME multipart/form-data packaging specified in [FORMDATA].

    For SMTP transport, the receipt and signed receipt functions are
    implemented using Message Dispostion Notifications [MDN] and Multipart/signed
    Message Disposition Notifications [AS1]. As mentioned previously, for HTTP transport,
    generalization  of the Message Disposition Notification is useful. The multipart/report [REPORT]
    MIME package is retained to support these generalizations, and multipart/
    signed packages are used to support signatures over these generalized receipts.

    Finally, within the HTTP transport context, it is useful
    to make use of Transport Layer Security [TLS] to provide
    privacy. Compression can be provided using HTTP content-codings
    [HTTP], sections 3.5, 14.3, 14.12]. (Content codings are not be be
    confused with the MIME concept of content transfer encodings.)

    A variety of other minor differences (for example, absence of content-transfer-encoding)
    are noted below and summarized in the concluding section.

   1.2 Overall operation

    A HTTP POST operation [HTTP] is used to send appropriately packaged
    EDI or other business data. The Request-URI ([HTTP], section 9.5)
    identifies a process to unpack and handle the message data
    and to generate a reply for the client that contains a message
    disposition acknowledgement or a multipart/report, signed
    or unsigned, and possibly other turnaround transactions.
    This request/reply transactional interchange provides secure,
    reliable, and authenticated transport for EDI or other business
    data using HTTP; the security protocols and structures used also
    support auditable records of these transmissions, acknowledgements,
    and authentication.

2.Stages and Details of  HTTP EDI Transmission and Acknowledgment

    An EDI data file or stream is first structured into one of the
    message templates described in [AS1], sections 4.2.1 to 4.2.4 or
    4.3.1 to 4.3.4 for PGP/MIME or S/MIME security. If TLS is to be used,
    the typical packaging will be that provided in 4.2.2 or 4.3.2;
    that is, a multipart/signed message will be created with no
    encryption in the message. Otherwise, if privacy
    is desired, message templates 4.2.4 or 4.3.4 are used.
    Content transfer encoding is not used and a content-length
    field is to be provided.

    If HTML-based POST is used (using the METHOD=POST attribute
    within the "FORM" tag) [HTML, 17 Forms], then the message templates
    will be packaged as the final part of a multipart/form-data.
    The metadata needed for application layer routing, identification,
    requesting a reply and other transaction operations
    can be packaged in message body parts in the multipart/form-data.
    The labels for the metadata values are found in the "name" parameter of
    the Content-Disposition header in each form-data part as discussed in
    [FORMDATA, section 3].

    In general, both HTTP servers and HTTP clients handling the message
    templates of [AS1] should be prepared to process these basic EDIINT
    data formats when they are embedded within MIME multiparts.

   2.1.1  Requesting MDN-based receipts

     For requesting MDN based receipts, the originator supplies
     metadata  using the syntax of   extension headers (the [SMTPMSG] header syntax)
     that precede  the message body.  The header "tags" are as follows:

      A Disposition-Notification-To header is added to indicate
      that a message disposition notification is requested
      in the reply to the POST request. This header is
      specified in [MDN].

      A Message-ID header is added to support message reconciliation,
      so that an Original-Message-Id value can be returned in the MDN
     body part of the receipt. (Receipts is here used to refer to the signed or unsigned
     multipart/report body parts.)

      Both "From" and "To" extension headers are to be supplied. The "From"
      value needs to have an email address as specified in [SMTPMSG] and
     [HTTP]. If other uses of "From" are needed, the generalized receipts
     to be next discussed should be used. There the role of From is replaced
     by tags not having a reserved HTTP and SMTP usage.

     Other headers, especially "Subject" and "Date", should be supplied;
     the values of these headers are often mentioned in the human-readable
     section of a MDN  to aid in identifying the original message.

     A Disposition-Notification-Options header is used to request
     a signed message disposition notification. The parameters
     used to select protocols for signed message disposition
     notification are found in [AS1].

     A  Receipt-delivery-option is a header whose value is a URL that indicates how
     the receipt is to be delivered. While the default mode of operation
     within HTTP transport is to return the receipt
     (be it MDN, signed MDN, generalized report receipt,
     or signed report receipt) in the reply body, asynchronous reply is
     allowed through use of this name. The "mailto", "http", and "https" will
     be the more common types of value for this information. If this header
     is found and contains the value "default" (case-insensitive), then
     any receipt is to be returned in the reply to the request.

   2.1.2  Requesting Generalized Receipts

     For requesting generalized receipts using the MIME template for
     multipart/reports [REPORTS], the following metadata can
     be supplied using the syntax of the name parameter within the
     Content-Disposition header of the multipart/form-data structure.
     Within HTML, these names correspond to the name attribute within
     the INPUT element, where the "type" attribute has a "text" value.
     [HTML], section  .

     The To name contains an identifier identifying the
     intended recipient of a data exchange and may be
     D&B D-U-N-S number [DUNS]  or other agreed upon
     identifier system. Applications should allow users to
     configure these elements in the automated HTTP agents
    processing these values. For example, the body
    part MIME header line looks like the following line:

          Content-Disposition: form-data; name="To"

    The From name contains a textual value identifying
    the sender of a data exchange, such as the a D&B D-U-N-S  number [DUNS]
    as in [GISB].   Because "From" has a specified use within [HTTP], the
    From name parameter is not to be considered equivalent to the
    extension header. If an extension header "From" is to be used it should
    within HTTP, it should conform to the usage, syntax, and semantics of
    [HTTTP] section 14.22. The extension header counterpart of the
    sender of a data exchange is the extension header version of
    " Receipt-disposition-to".

    The Input-format name identifies the type of data contained in a data file.

    The Agent name parameter indicates the network or agent where the data
    exchange originated.

    The Application  name identifies the application used to process the data next
    (after the URI-request process has finished with the stream).

    The DateTime name provides the date and time the data was created
    and uses the format specified in [SMTPMSG] as updated by
    RFC 1123.

    The RefNum is an integer value used to uniquely identify the
    communication exchange and is in a textual format. The RefNum is
    similar to the Message-ID and Content-Id headers of SMTP that
    are used in constructing values in receipts based on  MDNs.

    The UserParam is a user defined parameter.

    GISB-Version is a protocol version number [GISB].

    Transaction-set is an optional data element identifying the EDI transaction.

    Input-data is the sending side's local file system name for the file being sent

    Receipt-disposition-to name contains an identifer
    identifying the party to receive positive notification of delivery.
    This identifier may be a D&B D-U-N-S number [DUNS] as in [GISB].

    Receipt-delivery-option is a URL containing a value indicating how
    the receipt is to be delivered. While the default mode of operation
    within HTTP transport is to return the receipt
    (be it MDN, signed MDN, generalized report receipt,
    or signed report receipt) in the reply body, asynchronous reply is
    allowed through use of this name. The "MAILTO", "HTTP", and "HTTPS" will
    be the more common types of value for this information.
    For the HTTP and HTTPS schemes, the POST method is
    to be used.

    Receipt-security-selection is a name that indicates the
    protocol and algorithm choices for a digital signature
    over the receipt. Signatures are always in multipart/signed
    packages. The format for protocol and algorithm choices is
    that used in [AS1] and [MDN].

    Disposition-Notification-To is a name that, if present, indicates
    that the MDN style of receipt is to be used. It may have values
    other than email addresses when it is found as a name parameter
    in a form-data body part, such as a D-U-N-S number. When this
    tag is used in HTTP extension headers or in SMTP headers it follows
    the MDN usage.

    Disposition-notification-options identifies characteristics of message
    disposition notification in accordance with [AS1] and [MDN].

    Application are encouraged to support handling all metadata values
    whether they make use of the name parameter syntax within a
    multipart/form-data or whether they use the message header syntax
    used in SMTP or HTTP headers [SMTPMSG]. If metadata items are
    repeated in extension headers and in form-data parts, but the
    values are not the same, the extension header values will be
    selected for use.

   The presence of the metadata value "Receipt-Disposition-To"
    using the extension header syntax indicates a request
    for a generalized receipt. This value also fulfills the
    role of "From" when a value other than an email address
    needs to be used.  The value in Receipt-Disposition-To
    may have no significance for setting up the transport connection.
    Therefore, the extension header " Receipt-delivery-option"
     should be used to provide that information as a URL or as
     the special value "default." For signed generalized receipts,
     an extension header of  "Receipt-security-selection" should
     be added to indicate the desired security protocol for the
     multipart/signed over the multipart/report.

      2.1.3 Summary of Receipt request options

     In summary, the receipt request and construction process now has
     the following options. Receipt requests are made by conveying metadata
     values using a syntax of either the name parameter in a multipart/form-data's
     Content-Disposition headers or using a syntax of extension headers.
     Both MDN and generalized receipts can be requested in either way,
     though using an extension header syntax and requesting a MDN receipt
     means restricting the "From" values to email addresses. And either type
     of receipt comes in signed or unsigned versions. Finally, receipts may
     be delivered synchronously (HTTP only) or asynchronously by using
      the  " Receipt-delivery-option" header.


   [  TBD or omit

   >> ADD alternative XML syntax for metadata options
   >> as discussed at  May alignment conference?
    >> No known submissions to editors on this yet
    >> One editor thinks this is enough for AS2 unless it
   >>  clearly helps in specifying the semantics of the
   >> machine usable part of the multipart/report.
   >> Nothing much is really gained by yet another
  >> syntax for the client  to use in conveying
  >> metadata.-- there are already two.
  ]

    2.2  Sending EDI in HTTP Client Requests using POST

    For sending EDI, the following protocol elements are typically
    present: a request line ([HTTP], section 5.1), entity headers, a
    CRLF pair to mark the end of the entity headers, followed by the
    message-body.

    The request line will have the form: "POST Request-URI HTTP/1.1",
    with spaces and followed by a CRLF. The Request-URI is typically
    exchanged out of band, as part of setting up a bilateral
    trading partner agreement. Applications should be prepared
    to deal with an initial reply containing a status indicating a need
    for authentication of the usual types used for authorizing access
    to the Request-URI ([HTTP], section 10.4.2 and elsewhere).

    Automation of this process is not discussed in this document
    but might involve obtaining a session URL from a page requesting
    authentication and possibly other information about proposed
    EDI standard versions and other trading conventions to be used.

    The request line is followed by entity headers specifying content length
    ([HTTP] section 14.14) and content type [HTTP] section 14.18.
    The Host request header ([HTTP] sections 9 and 14.23) is also included.

    The entity or extension headers used for requesting a MDN
     (unsigned or signed) have previously been mentioned,
    as have those  ("To" "From" "Message-Id") that are needed as values
    for MDN fields or for other receipt requests.

    For generalized receipts based on the multipart/report content type,
    the metadata can be the values found  in  extension headers,
    but can also  be placed  in body parts of a multipart/form-data
    using "name" parameters in the content-disposition header.

   Finally, the payload is found in any of the message patterns
   of  [AS1]  sections 4.2.1 to 4.2.4 or  4.3.1 to 4.3.4 for PGP/MIME or S/MIME security.
   These payloads may arrive as the final part of a multipart/form-data
    or may even be enclosed in some other multipart.

    2.3 Using Transport Layer Security

    To use Transport Layer Security [TLS], the request-URI should indicate
    the appropriate scheme value, HTTPS. Usually only a multipart/signed
    message body would be sent using TLS, as encrypted message bodies
    would be redundant. Encrypted message bodies are not prohibited, however.
    For asynchronous receipt delivery requests,  use   the  " Receipt-delivery-option" header
    with a URL value making use of the HTTPS scheme to obtain security privacy.

    2.4  Response Status Codes in Replies

    The status line for response to errors in the POST request line
    will be provided by a status line with the following protocol
    elements present ( [HTTP], section 6.1 ) : HTTP version (normally,
    HTTP/1.1), a status code, reason phrase, and CRLF.

    The status codes return status concerning HTTP operations. For example,
    the status code 401, together with the WWW-Authenticate header,
    is used to challenge the client to repeat the request with an
    Authorization header.   Other explicit status codes are
    documented in [HTTP], sections 6.1.1 and throughout section 10.
    For errors in the request-URI, 400 ("Bad Request"),
    404 ("Not Found") and similar codes are appropriate status codes.
    These codes and their semantics are specified by [HTTP].
    A careful examination of these codes and their semantics
    should be made before implementing any retry functionality
    that is described below; specifically, retries should not
    be made if the error is not transient or if retries are
    explicitly discouraged (for real authentication failures, for example.)

    2.5  Receipt Reply

    The details of the response to the POST command vary depending
    upon whether  a receipt has been requested and upon what kind of receipt
    has been requested.

    With no extended header requesting a receipt, and no errors
    accessing the request-URI specified processing, the status
    line in the Response to the POST request should be in the
    200 range. Status codes in the 200 range should also be used when
    an entity is returned (a signed receipt in a multipart/signed
    content type or an unsigned receipt in a multipart/report).
     That is, even when the disposition of the data was an error condition
    at the authentication, decryption or other higher level, the
    HTTP status code should indicate success at the HTTP level.

    The HTTP server-side application may respond with an unsolicited
    multipart/report as a message body that the HTTP client
    might not have solicited, but this may be discarded by the
    client. Applications should avoid emitting unsolicited receipt replies
    because bandwidth or processing limitations might have led
    administators to suspend asking for acknowledgements.

    When a Disposition-Notification-To extension header is present
    in the POST request entity headers, then entity headers for
    the MDN should be included. The content type for the MDN receipt
    ( multipart/report [REPORT] or multipart/signed [SECURITY])
    should be included in the Response entity headers. The

    The basic responsibilities of responding to requests are discussed
    at length in [AS1] section 5, and in detail within section 5.2.1.

    2.5.1  MDN based Receipts and Signed MDN Receipts

    Message Disposition Notifications, when used in the HTTP reply
    context, will closely parallel a SMTP MDN. For example,
    the disposition field is a required element in the machine
    readable second part of a multipart/report for a MDN.
    The final-recipient-field([MDN] section 3.1) value should
    be derived from the entity headers of the request
    If the "To" field is missing, for signed messages,
    the value for Original-recipient may be the email
    address field from the signer's X.509 attribute for
    email addresses, if that value is available.
    For a MDN, an application must report the Message-ID
    of the request. The human readable part (the first
    part of the multipart/report) should include items
    such as the subject, date and other information
    when those fields are present in entity header fields following the
    POST request

    The HTTP reply should normally omit the third optional part of the
    multipart/report (used to return the original message or its
    headers in the SMTP context).

  2.5.2  Generalized Receipts and Signed Receipts

    In addition, a generalized receipt using the multipart/report [REPORT]
    and multipart/signed containing a multipart/report as the signed data
    is allowed. The basic structure of the multipart/report is used so that
    the first part is a "human-readable" message concerning the received
    message. The second part should be for automated process utilization
    so should at least possess some common Internet syntax for expressing
    names and values, such as the [SMTPMSG] header syntax, XML, or
    some MIME content type correlated with automated processing. The MDN
    requirements are removed for this second part but fields used in MDNs may
    be used here. The third part of the multipart report is usually omitted in the
    HTTP context, but would include the extension headers if used to provide
    diagnostic hints.  A multipart/signed over a multipart/report is constructed
    precisely in the same way as a multipart/signed over a MDN [AS1].

    To indicate a desire for a generalized receipt (which may be fulfilled
    by a MDN), the following metadata elements are to be included in
    the original message in either the extended header format or the
    form-data format:

    Receipt-delivery-option is either the key word (case-insensitive) value
    "default" or a URL that indicates how and where
    the receipt is to be delivered. While the default mode of operation
    within HTTP transport is to return the receipt
    (be it MDN, signed MDN, generalized report receipt,
    or signed report receipt) in the reply body, asynchronous reply is
    allowed through use of this metadata value. The  "MAILTO", "HTTP", and "HTTPS"
   will be the more common schemes found in the URL  value.

    Receipt-security-selection is a name that indicates the
    protocol and algorithm choices for a digital signature
    over the receipt. Signatures are always in multipart/signed
    packages. The format for protocol and algorithm choices is
    that used in [AS1] and [MDN].

    One metadata element should, if at all possible, be within the automated part.
    This is the Received-Content-MIC (also allowing X-Received-Content-MIC).
    This value is constructed and formatted as described in [AS1] and
    the syntax should be either RFC822:

          Received-Content-MIC: w7AguNJEmhF/qIjJw6LnnA==,rsa-md5

    or simple XML

          <ReceivedContentMic algid=rsa-md5 encode=base64 >
           w7AguNJEmhF/qIjJw6LnnA==
          </ReceivedContentMic>

    Any original metadata thought useful to include in the automated part
    may be reflected back using "Original-X", as in

           Original-Message-ID: <43141asfioufasd@somewhere.com>

    Otherwise the automated acknowledgement semantics are left open to further semantic
    specification by specific electronic commerce communities, such as in [GISB].


    2.6  Additional Reply Content

    In general, both HTTP servers and HTTP clients should be prepared
    to process the basic EDIINT data formats when they are embedded
    within MIME multiparts. This is true for HTTP request payloads
    as well as HTTP reply payloads.

    So, as previosuly mentioned, for HTML-based POSTS,
    any of the EDIINT templates described in [AS1], sections 4.2.1 to 4.2.4 or
    4.3.1 to 4.3.4 for PGP/MIME or S/MIME security, may be found as
    parts of a multipart/form-data.

    In addition, the response to the POST operation may include other MIME
    wrapped content besides an MDN Receipt, Signed MDN, Generalized Report
    Receipt or Signed Report Receipt. If a receipt was
    requested within the POST data, and additional content is to be
    returned, the receipt multipart/report must be combined with the
    other data using some MIME multipart pattern.
    Real-time EDI processing systems may use MIME
    multipart content-types to include a response EDI message,
    for example, a Quote in response to a Request-For-Quote transaction.

    Also, if requested, the sender may request an asynchronous mode
    for return of receipt. This mode is indicated by including the metadata
    for Receipt-delivery-option as explained above and choosing a
    URL rather than the value "default".


    2.7  Non-Repudiation of the POST Reply

    If the reply to a POST operation needs a MDN receipt for non-
    repudiation (for example, the reply includes content other than
    a receipt), the top-level headers in the response include
    the same headers required for POST data described above:
    Disposition-Notification-To, Message-ID, From, and To. Other
    headers described above used in a MDN should be included,
    for example, Date and Subject.

    The MDN receipt of the response data is returned using
    a subsequent POST operation. A POST operation used only
    to transmit an MDN should not include the Disposition-
    Notification-To receipt request, and only a 200 ("OK") response
    would be expected.

    An MDN in response to a reply may be combined with a
    subsequent EDI message sent with a POST operation, for example
    a Purchase-Order transaction in response to a Quote. The MIME
    multipart/mixed form is used to combine the MDN with the other
    data, the same as for a POST reply.


   2.8  Error Recovery

   If the HTTP client fails to read the HTTP server
   response data, the POST operation with identical content (including
   Message-ID) should be repeated, if the error condition is transient.
   The Message-ID on a POST operation can be reused if and only
   if all of the content (including the original Date) is identical.
   Details of the retry process -- including time intervals to pause, number of
   retries to attempt, timeouts for retrying -- are implementation dependent.

   Servers should be prepared to receive a POST with a repeated Message-ID.
   The MIME reply body previously sent should be resent, including the MDN
   and other MIME parts.



3. Referenced RFCs and their contribution

     3.1 RFC 2068 [HTTP] : The HyperText Transfer Protocol, HTTP,
     provides an application level protocol for distributed hypermedia
     information systems. This standard specifies the protocol HTTP/1.1.

     3.2 RFC 2246 [TLS] : Transport Layer Security
     Security specifies a protocol similar to SSL version 3 that provides
     communications privacy over the Internet.  Applications can
     communicate without eavesdropping, tampering, or message forgery.

     3.3 RFC 1847 [SECURITY] : MIME Security Multiparts

     This document defines security multiparts for MIME:
     multipart/encrypted and multipart/signed.

     3.4 RFC 1892 [REPORT] : Multipart/report

     This RFC defines the use of the multipart/report content type
     that the MDN RFC 2298 [MDN] presupposes.

     3.5 RFC 1767 [MIMEEDI] :  EDI Content

     This RFC defines the use of content type "application" for ANSI
     X12 (application/EDI-X12), EDIFACT (application/EDIFACT) and
     mutually defined EDI (application/EDI-Consent).

     3.6 RFC 2015 [MIMEPGP] : PGP/MIME

     This RFC defines the use of content types
     "multipart/encrypted", "multipart/signed", "application/pgp
     encrypted" and "application/pgp-signature" for defining MIME PGP
     content.

     3.7 RFC 2045, 2046, and 2049 [MIME] : MIME

     These are the basic MIME standards, upon which all MIME related RFCs
     build, including this one.  Key contributions include definition of
     "content type", "sub-type" and "multipart", as well as encoding
     guidelines,  which establishes 7-bit US-ASCII as the canonical
     character set to be used in Internet messaging.

     3.8 RFC 2298 [MDN] : Message Disposition Notification

     This RFC defines how a message disposition notification
     (MDN) is requested, and the format and syntax of the MDN.
     The MDN is the basis upon which receipts and signed receipts
     are defined in this and in [AS1].

     3.9 RFC 2311 [SMIMEV2] : S/MIME Version 2 Message Specification
     This specification describes how MIME shall carry PKCS7 1.5
     envelopes.

     3.10 RFC XXXX X [AS1] : MIME-based Secure EDI
     This applicability statement describes security patterns,
     MIME content types, and acknowledgement policies and
     mechanisms for EDI or business data transport.


4.  Other differences to notice in HTTP and SMTP based transport

    For HTTP version 1.1, TCP persistent connections are the default,
    ( [HTTP] sections 8.1.2, 8.2, and 19.7.1).

    A number of other differences exist because HTTP does not
    conform to MIME [MIME] as used in SMTP transport. Relevant
    differences are summarized below.

  4.1 Unused MIME headers and operations

   4.1.1  Content-Transfer-Encoding not used in HTTP transport

    HTTP can handle binary data and so there is no need to use
    the Content transfer encodings of MIME [MIME]. This difference
    is discussed in [HTTP] section 19.4.4.

   4.1.2  Epilogue must be empty

    The EBNF for a multipart [MIME] RFC 2046, section 5.1.1 allows
    a multipart to have trailing octets after the close delimiter.
    In [HTTP] section 3.7.2, it is explicitly noted that multiparts
    must have null epilogues.

   4.1.3  Lengthy message bodies

    In [AS1], section 5.4.1, options for large file processing are
    discussed for SMTP transport. For HTTP, large files should
    be handled correctly by the TCP layer. However, [HTTP] sections
    3.5 and 3.6 discuss some options for compressing or chunking
    entities to be transferred. Section 8.1.2.2 discusses a
    pipelining option that is useful for segmenting large
    amounts of data.

  4.2 Differences in MIME or other headers or parameters used

   4.2.1  Content-Length

    Because connections are persistent, closing a connection
    cannot be used to indicate the end of an entity. Therefore,
    [HTTP] sections 4.4 and 14.14 indicate the need for a
    Content-Length entity header in a request.

   4.2.2 Final and Original Recipient

    The final and original recipient distinction should not
    arise for HTTP transport because SMTP aliases and mailing
    lists should not be used.

   4.2.3 Message-Id and Original-Message-Id

    The Message-Id and Original-Message-Id distinction should not
    arise for HTTP transport because SMTP MTA alterations should
    not occur.

   4.2.4 Host header

    The host request header field must be included in the
    POST request made when sending business data. This field
    is to allow one server IP address to service multiple
    hostnames, and potentially conserve IP addresses.
    See [HTTP], sections 14.23 and 19.5.1.

5. Acknowledgments

   Carl Hage, Karen Rosenfeld, Chuck Fenton, Dick Brooks,
   and many others  have provided valuable suggestions
    improving this applicability statement.

6. References

[MIME]  N. Borenstein,  N.Freed, "Multipurpose Internet Mail Extensions (MIME)
     Part One: Format of Internet Message Bodies", RFC 2045,
     December 02, 1996.

     N. Borenstein, N.Freed, "Multipurpose Internet Mail Extensions (MIME)
     Part Two: Media Types", RFC 2046, December 02, 1996.

     N. Borenstein, N.Freed, "Multipurpose Internet Mail Extensions (MIME)
     Part Five: Conformance Criteria and Examples", RFC 2049 , December 02,
     1996.

[MIMEEDI]  D. Crocker, "MIME Encapsulation of EDI Objects",  RFC 1767,  March
     2, 1995.

[SMTPMSG]  D. Crocker, "Standard for the Format of ARPA Internet Text
     Messages", STD 11,  RFC 822,  August 13, 1982.
    (Also RFC 1123 provides important updates on date and time formats
    as well as email addresses.)

[MIMEPGP]  M. Elkins, "MIME Security With Pretty Good Privacy (PGP)",  RFC
     2015, Sept. 1996.

[MDN]  R. Fajman, "An Extensible Message Format for Message Disposition
     Notifications", RFC 2298, March 1998.

[SECURITY]  J. Galvin, S. Murphy, S. Crocker, N. Freed,  "Security Multiparts
     for MIME: Multipart/Signed and Multipart/Encrypted", RFC 1847, Oct.
     3, 1995

[SMTP]  J. Postel, "Simple Mail Transfer Protocol",  STD 10, RFC 821,
     August 1, 1982.

[SMIMEV2]  S. Dusse, P. Hoffman, B. Ramsdell, L. Lundblade, L. Repka,
     "S/MIME Version 2 Message Specification", RFC 2311.

[EDIINT]  C. Shih, "Requirements for Interoperable Internet EDI",
     Internet draft: draft-ietf-ediint-req06.txt.

[REPORT] G. Vaudreuil, "The Multipart/Report Content Type for the Reporting
     of Mail System Administrative Messages",  RFC 1892,
     January 15, 1996.

[HTTP] R. Fielding, J.Gettys, J. Mogul, H. Frystyk, T. Berners-Lee,
     "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068,
     January 1997.

[AS1] C. Shih, "MIME-based Secure EDI", Internet draft:
     draft-ietf-ediint-as1-08.txt.

[TLS] T. Dierks,C. Allen, "The TLS Protocol Version 1.0" RFC 2246, January 1999 .

[FORMDATA] L. Masinter, "Returning Values from Forms:  multipart/form-data", RFC 2388,
     August, 1998.

[HTML]  D. Raggett, A. Le Hors, I. Jacobs. "HTML 4.0
      Specification", World Wide Web Consortium Technical Report
      "REC-html40", December, 1997. <http://www.w3.org/TR/REC-html40/>

[GISB] Gas Industry Standards Board, "Electronic Delivery
       Mechanism Related Standards", Version 1.3 July 31, 1998


7.  Authors' Addresses

Chuck Shih
Chuck.Shih@gartner.com

Dale Moberg
dale_moberg@stercomm.com
Sterling Commerce
4600 Lakehurst Ct.
Dublin, OH 43016 USA

Rik Drummond
drummond@onramp.net
The Drummond Group
5008 Bentwood Ct.
Ft. Worth, TX 76132 USA



Appendix A. Example Exchange.

   NOTE:  This example is provided as illustration only
   If the example conflicts with the previous text,
   the example is wrong.

   Likewise, the use of entity or extension fields in
   this example is not to be construed as a definition for those type
   names or extension fields.


A.1 Sending a multipart signed for trading partner 1 back to
trading partner 2. "#" indicates a comment line.

POST https://tp2server.company2.com/cgi-bin/tp1drawer.pl HTTP/1.1
Host: tp2server.company2.com
From: tp1@company1.com
To: tp2@company2.com
Date: Tue, 06 Nov 2001 12:53:01 UT
Subject: Purchase orders for 6 November 2001
Message-Id: <20011106@company1.com>
Disposition-Notification-To: tp1@company1.com
# continuation lines not used in actual HTTP protocol data unit
Content-Type: multipart/signed; boundary="20011106RsXgYlvCNW" ;
 protocol=application/pkcs7-signature;  micalg=rsa-md5
Content-Length: 3056

--20011106RsXgYlvCNW
Content-Type: application/edi-x12
Content-Disposition: Attachment; filename=rfc1767.dat
Content-Length: 2605

ISA ...
# EDI transaction data
IEA  ...
--20011106RsXgYlvCNW
Content-Type: application/pkcs7-signature
Content-Length: 804

# omitted binary data
--20011106RsXgYlvCNW--

A.2
Returning a signed MDN (using the previously established TLS security)
from trading partner 2 back to trading partner 1.
"#" indicates a comment line.

HTTP/1.0 200 OK
Server: HTTPEDI/1.1
Content-type: multipart/signed;
Content-Length: 1200

--boundary1
Content-type: multipart/report
Content-length: 1133

--boundary2
Content-type: text/plain
Content-length: 85

Message <20011106@company1.com> was authenticated;
EDI processing was initiated.
--boundary2
Content-type: message/disposition-notification
Content-length: 213

Reporting-UA: Company2UA
Original-Message-Id: <20011106@company1.com>
Original-Recipient: tp2@company2.com
X-Received-Content-MIC: w7AguNJEmhF/qIjJw6LnnA==,rsa-md5
Disposition: MDN-sent-automatically/processed

--boundary2--

--boundary1
Content-Type: application/pkcs7-signature
Content-Length: 560

# Signature data omitted
--boundary1--


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