Content Negotiation for Messaging Services based on Email
RFC 3297

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 05

Network Working Group                                           G. Klyne
Request for Comments: 3297                        Clearswift Corporation
Category: Standards Track                                     R. Iwazaki
                                                             Toshiba TEC
                                                              D. Crocker
                                             Brandenburg InternetWorking
                                                               July 2002

       Content Negotiation for Messaging Services based on Email

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This memo describes a content negotiation mechanism for facsimile,
   voice and other messaging services that use Internet email.

   Services such as facsimile and voice messaging need to cope with new
   message content formats, yet need to ensure that the content of any
   given message is renderable by the receiving agent.  The mechanism
   described here aims to meet these needs in a fashion that is fully
   compatible with the current behaviour and expectations of Internet
   email.

Table of Contents

   1. Introduction................................................... 3
     1.1 Structure of this document ................................. 4
     1.2 Document terminology and conventions ....................... 4
        1.2.1 Terminology............................................ 4
        1.2.2 Design goals........................................... 5
        1.2.3 Other document conventions............................. 5
   2. Background and goals........................................... 5
     2.1 Background ................................................. 5
        2.1.1 Fax and email.......................................... 5
        2.1.2 Current facilities in Internet Fax..................... 6
     2.2 Closing the loop ........................................... 6

Klyne, et. al.              Standards Track                     [Page 1]
RFC 3297      Content Negotiation for Messaging Services       July 2002

     2.3 Goals for content negotiation .............................. 8
   3. Framework for content negotiation..............................10
     3.1 Send data with an indication of alternatives ...............11
        3.1.1 Choice of default data format..........................12
        3.1.2 MDN request indicating alternate data formats..........12
        3.1.3 Information about alternative data formats.............13
     3.2 Receiver options ...........................................14
        3.2.1 Alternatives not recognized............................14
        3.2.2 Alternative not desired................................14
        3.2.3 Alternative preferred..................................14
     3.3 Send alternative message data ..............................16
     3.4 Confirm receipt of resent message data .....................17
   4. The Content-alternative header.................................18
   5. The Original-Message-ID message header.........................18
   6. MDN extension for alternative data.............................19
     6.1 Indicating readiness to send alternative data ..............19
     6.2 Indicating a preference for alternative data ...............20
     6.3 Indicating alternative data is no longer available .........21
     6.4 Indicating loss of original data ...........................22
     6.5 Automatic sending of MDN responses .........................22
   7. Internet Fax Considerations....................................22
   8. Examples.......................................................23
     8.1 Sending enhanced Internet Fax image ........................23
     8.2 Internet fax with initial data usable ......................27
     8.3 Negotiate to lower receiver capability .....................28
     8.4 Sending an alternative content type ........................32
   9. IANA Considerations............................................36
     9.1 New message headers ........................................36
     9.2 MDN extensions .............................................36
        9.2.1 Notification option 'Alternative-available'............36
        9.2.2 Notification option 'Alternative-not-available'........36
        9.2.3 Disposition modifier 'Alternative-preferred'...........37
        9.2.4 Disposition modifier 'Original-lost'...................37
   10. Internationalization considerations...........................37
   11. Security Considerations.......................................37