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IETF fax WG                             G. Klyne, Content Technologies
Internet draft                                             [[[et al]]]
                                                       22 October 1999
                                                   Expires: April 2000


          Timely Delivery for Facsimile Using Internet Mail
               <draft-ietf-fax-timely-delivery-00.txt>

Status of this memo

  This document is an Internet-Draft and is in full conformance with
  all provisions of Section 10 of RFC 2026.

  Internet-Drafts are working documents of the Internet Engineering
  Task Force (IETF), its areas, and its working groups.  Note that
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  West Coast).

Copyright Notice

  Copyright (C) The Internet Society 1999.  All Rights Reserved.

Abstract

  This proposal is to describe a way to accomplish timely delivery of
  e-mail messages, with deterministic service quality guarantee,
  while preserving the traditional roles and responsibiltiies of the
  agents involved in e-mail transfers.

  It is essentially a profile of the DSN and DELIVERBY extentions for
  ESMTP, [[[and possibly]]] a new extension for establishing the
  deerministic service guarantee.









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Content Negotiation for Internet Fax                   22 October 1999
<draft-ietf-fax-timely-delivery-00.txt>


  NOTE: This is a first and very preliminary version of
  specification, rapidly drafted to indicate a possible way forward
  to achieve the timely delivery requirement for full mode Internet
  fax.  The content is very rough, and the intent at this time is to
  indicate just the outline of a mechanism.  Please address comments
  to major structural and semantic issues.


Table of contents

1. Introduction.............................................2
  1.1 Structure of this document ...........................2
  1.2 Document terminology and conventions .................2
  1.3 Discussion of this document ..........................3
2. Background and goals.....................................3
  2.1 Background ...........................................3
  2.2 Goals for timely delivery ............................4
3. Framework for timely delivery............................4
  3.1 Transmitting a message for timely delivery ...........4
  3.2 Relaying a message ...................................5
  3.3 Accepting a message by the final MTA .................6
4. Compliance-required ESMTP extension......................7
5. DSN reporting extensions.................................7
6. Notes....................................................7
7. Examples.................................................7
8. IANA Considerations......................................8
9. Internationalization considerations......................8
10. Security considerations.................................8
11. Acknowledgements........................................8
12. References..............................................8
13. Authors' addresses......................................9
Appendix A: Amendment history...............................9
Full copyright statement....................................9



1. Introduction

1.1 Structure of this document

  [[[TBD]]]

1.2 Document terminology and conventions

  [[[TBD]]]

       NOTE:  Comments like this provide additional nonessential
       information about the rationale behind this document.
       Such information is not needed for building a conformant






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       implementation, but may help those who wish to understand
       the design in greater depth.

  [[[Editorial comments and questions about outstanding issues are
  provided in triple brackets like this.  These working comments
  should be resolved and removed prior to final publication.]]]

1.3 Discussion of this document

  Discussion of this document should take place on the content
  negotiation and media feature registration mailing list hosted by
  the Internet Mail Consortium (IMC):

  Please send comments regarding this document to:

      ietf-fax@imc.org

  To subscribe to this list, send a message with the body 'subscribe'
  to "ietf-fax-request@imc.org".

  To see what has gone on before you subscribed, please see the
  mailing list archive at:

      http://www.imc.org/ietf-fax/


2. Background and goals

2.1 Background

  Traditional e-mail [2] is open-loop.  The sender of a message
  normally has no certainty if or when a message is delivered.  (A
  separate memo [6] contains a discussion of some open- and closed-
  loop issues in e-mail.)

  To be more than just a hint to the message transfer system, timely
  delivery requires a deterministic confirmation mechanism, to close
  the loop.  This is provided by DSN [4].

  Three kinds of timeliness can be identified:

  (a)  timely delivery to the receipient

  (b)  timely notification to the sender of delivery

  (c)  timely notification to the sender that the message has been
       processed

  This proposal focuses on (a) and (b).  A separate proposal is under
  consideration to address the final case (c).





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  The DELIVERBY extension [5] provides a mechanism to ensure timely
  delivery of a message.

  From the sender's point of view, timely confirmation of delivery is
  the most desirable requirement.

  [[[Need to consider how timely confirmation (i.e. delay in the
  return path transfer of the confrmation) is handled]]]

2.2 Goals for timely delivery

  The primary goal is to provide a mechanism that allows a consenting
  parties to establish a relationship with guarenteed delivery within
  a specified time, or notification that the delivery was not
  achieved.

  Further goals are:

  o  Deterministic behaviour.

  [[[TBD]]]


3. Framework for timely delivery

  Timely delivery is achieved through a number of ESMTP extensions
  used in concert:

  - Deivery Status Notification ("DSN") [RFC 1891]

  - Deliver-by ("DELIVERBY") []

  - Compliance-required [[[NEW!]]] [[[if needed: deliver-by looks
  nearly sufficient.]]]

  The confirmation loop for succesful delivery looks something like
  this.  The path through MTAs taken by the confirmation response is
  not defined, and may be different from the forward path of the
  original message.

     +-----------+     +--------+     +--------+     +---------+
     |Originating|-->--|Relaying| ... |Relaying|-->--|Receiving|
     |    MTA    |     |  MTA   |     |  MTA   |   --|   MTA   |
     +-----------+     +--------+     +--------+  |  +---------+
            |                                     |       |
     +-------------+                              |  +---------+
     | Originating |--<--  ...   ....   ...  --<--   |Receiving|
     |     MUA     |                                 |   MUA   |
     +-------------+                                 +---------+






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3.1 Transmitting a message for timely delivery

  A transmitted message for which timely delivery is required MUST
  include the following:

  - an ENVID parameter on the MAIL command, per DSN [4]

  - a NOTIFY=SUCCESS,FAILURE parameter on the corresponding RCPT
  command, per DSN [4]

  - an ORCPT parameter on the MAIL command, per DSN [4]

  - a 'BY' parameter on the corresponding RCPT command, per [5]

  - a COMPLIANCE-REQUIRED parameter on the corresponding RCPT, as
  described below

  The message MUST NOT be transmitted to any MTA that does not
  indicate support for all of these extensions in its response to the
  EHLO command.  In this case, a negative delivery status report MUST
  be generated indicating the non-compliant MTA, the extensions that
  it does not support, and the name of the reporting MTA (per DSN,
  using the non-compliance reporting extensions noted below).

3.2 Relaying a message

  An MTA that relays a message for timely delivery MUST support all
  of the ESMTP extensions noted above, otherwise it should not
  receive the message in the first place.  When a relaying MTA
  accepts a message (by its 2xx status response to receipt of the
  message data), it becomes responsible for its onward delivery,
  including satisfying all of the options associated with the
  message.

  In order to relay a message, an MTA must note when the message was
  received, note the time when the attempt to transmit the message to
  the next MTA is initiated, and reduce accordingly the time interval
  used for the 'deliver-by' parameter (see note below on handling
  fine-grained timing requirements).

  If the deliver-by interval is reduced to less than zero, (or less
  than some system-configurable value indicating that delivery within
  the indicated interval is unlikely to be achieved) then the message
  MUST NOT be relayed.  Instead, a negative  delivery status report
  MUST be generated indicating that the time for delivery of the
  message has expired, and the reporting MTA (per DSN, using the
  deliver-by extensions and/or non-compliance reporting extensions
  noted below).

  [[[Remove duplication between above and DELIVERBY spec]]]





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  If the first attempt to relay a message fails, the relaying MTA MAY
  assume that delivery within the desired time will not be achieved,
  and immediately indicate a delivery failure, indicating the name of
  the next-hop MTA.  Alternatively, the relaying MTA may wait and
  retry the transmission, provided that the retry attempt will be
  performed within the remaining deliver-by period;  if the
  transmission cannot be completed after one or more such retries
  then a negative DSN should be generated as noted above.

  In all cases, any DSN generated should indicate the number of
  retries attempted (where 0 means no retries).

  The choice to retry or not retry is installation dependent.
  Effectively, when a relay does not retry, any reposibility for
  overcoming the delivery failure is passed back to the original
  sender.  This strategy may be appropriate for cases where very
  rapid delivery is required or expected.

  [[[Need to limit the number and/or frequency of retries?]]]

3.3 Accepting a message by the final MTA

  The MTA that accepts final delivery of a message has responsibility
  for passing the message to a Mail User Agent.  The exact mechanism
  by which this is achieved is a local matter, and not defined here
  or by the Internet e-mail specifications.  The final MTA is also
  responsible for generating any successful DSN message.

  Before generating a DSN message, the final MTA must ensure that all
  of the conditions for delivery of the message have been achieved.

  Specifically, it should  ensure that final delivery to the MTA will
  be completed within the deliver-by interval indicated.  Exactly
  what constitutes final delivery to the MTA may depend somewhat on
  the nature of the MTA:  in the simplest case, depositing the
  message in a local mailbox probably constitutes final delivery;  a
  more complex case would be that of a fax offramp:  in this case it
  may be reasonable for final delivery to be completion of a
  successful outdial and transmission of the fax.

  [[[DISCUSS:  In environments where the timing of final delivery of
  the message is outside the control of the final MTA (e.g. the time
  required for an outdial, or waiting for a client to collect the
  message), an interim DSN report may be generated indicating that
  the message has been received pending final delivery.   This report
  bshould be clear whether final delivery is dependent on the
  receiving user (e.g. mail collection) or some other unknown
  infrastructure delay (e.g. fax out-dial or external e-mail
  environment).]]]






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  [[[I think the above is verging on trying to be too clever, getting
  too far into MDN teritory]]]


4. Compliance-required ESMTP extension

  [[[TBD]]]

  Essentially, the semantics will be to REQUIRE conformance to any
  SMTP extensions used for delivery to be successfully completed.

  [[[I am thinking the required extensions should be listed in the
  RCPT command; e.g. COMPLIANCE=DSN,DELIVER-BY]]]


5. DSN reporting extensions

  - Extension not supported

  - Delivery time exceeded

  - Delivered for further transmission:  final confirmation pending
  [[[???]]]

  - Delivered for collection by user:  final confimation pending
  [[[???]]]


6. Notes

  [[[These are placeholders for further discussion]]]

  - Use of alternative port (e.g. like message submission).

  - Scalability analysis.  Required state information -- all at the
  edges?

  - Discussion of race conditions.  Indeterminacy in time for status
  response to reach sender.  Message duplication as the worst case.

  - Return path different from forward path.

  - Handling fine-grained timing requirements (deliver-by
  modification and implementation techniques).  Must assume deliver-
  by interval is large relative to normal network transit times.

  - Partial non-delivery:  failure to some recipients.  Must be
  handled, since all-or-nothing cannot be imposed within the SMTP
  transfer environment.






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7. Examples

  [[[TBD]]]


8. IANA Considerations

  [[[TBD: ESMTP and DSN extension registrations]]]


9. Internationalization considerations

  [[[TBD?]]]


10. Security considerations

  [[[TBD]]]


11. Acknowledgements

  [[[TBD]]]


12. References

[1]  RFC 2542, "Terminology and Goals for Internet Fax"
     L. Masinter, Xerox Corporation
     March 1999.

[2]  RFC 821, "Simple Mail Transfer Protocol"
     Jonathan B. Postel, ISI/USC
     August 1982.

[3]  (SMTP extensions)

[4]  RFC 1891, "SMTP Service Extension for Delivery Status
     Notifications"
     K. Moore, University of Tennessee
     January 1996.

[5]  DELIVERBY: <draft-newman-deliver-02.txt>

[6]  <draft-ietf-fax-content-negotiation-00.txt>

[7]  RFC 2234, "Augmented BNF for Syntax Specifications: ABNF"
     D. Crocker (editor), Internet Mail Consortium
     P. Overell, Demon Internet Ltd.
     November 1997.





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13. Authors' addresses

  Graham Klyne (editor)
  Content Technologies Ltd.
  1220 Parkview,
  Arlington Business Park
  Theale
  Reading, RG7 4SA
  United Kingdom.
  Telephone: +44 118 930 1300
  Facsimile: +44 118 930 1301
  E-mail:    GK@ACM.ORG

  [[[et. al.  TBD]]]


Appendix A: Amendment history

  00a  22-Oct-1999  Memo initially created.

  TODO:




Full copyright statement

  Copyright (C) The Internet Society 1999.  All Rights Reserved.

  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain
  it or assist in its implementation may be prepared, copied,
  published and distributed, in whole or in part, without restriction
  of any kind, provided that the above copyright notice and this
  paragraph are included on all such copies and derivative works.
  However, this document itself may not be modified in any way, such
  as by removing the copyright notice or references to the Internet
  Society or other Internet organizations, except as needed for the
  purpose of developing Internet standards in which case the
  procedures for copyrights defined in the Internet Standards process
  must be followed, or as required to translate it into languages
  other than English.

  The limited permissions granted above are perpetual and will not be
  revoked by the Internet Society or its successors or assigns.










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  This document and the information contained herein is provided on
  an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
  ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
  THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
  WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

















































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