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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 7259

Network Working Group                                     P. Saint-Andre
Internet-Draft                                                       XSF
Intended status: Informational                        September 13, 2007
Expires: March 16, 2008

                       The Jabber-ID Header Field

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Copyright Notice

   Copyright (C) The IETF Trust (2007).


   This document defines a header field that enables the author of an
   email message to include a Jabber Identifier in the message header
   block for the purpose of associating the author with a particular
   Extensible Messaging and Presence Protocol (XMPP) address.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Implementation  . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.1.  Inclusion . . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.2.  Generation  . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.3.  Processing  . . . . . . . . . . . . . . . . . . . . . . . . 5
     3.4.  Disposition . . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9

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1.  Introduction

   The Extensible Messaging and Presence Protocol (XMPP), documented in
   [XMPP-CORE], is a streaming XML technology that enables any two
   entities on a network to exchange well-defined but extensible XML
   elements (called "XML stanzas") in close to real time.  Given XMPP's
   heritage in the Jabber open-source community, one of the primary uses
   for XMPP is instant messaging and presence as documented in
   [XMPP-IM], and XMPP addresses are still referred to as Jabber
   Identifiers or Jabber IDs.

   Because almost all human users of Jabber/XMPP instant messaging and
   presence systems are users of email systems, it can be helpful for
   such users to specify their Jabber Identifiers in the email messages
   they author.  The Jabber-ID header field provides a standard location
   for that information.  Members of the Jabber instant messaging and
   presence community have been experimenting with this usage for
   several years.  As a result, this document provides informational
   documentation regarding the syntax and implementation of the
   Jabber-ID header field, including the information necessary to
   register the Jabber-ID field in the Provisional Message Header Field
   Registry maintained by the IANA.

   Naturally it may be beneficial to define a more general header field
   (or fields) that can be used by non-XMPP instant messaging and
   presence systems.  In all likelihood the result would be one header
   field encapsulating a URI that conforms to the "im:" scheme (see
   [CPIM]) and a second header field encapsulating a URI that conforms
   to the "pres:" scheme (see [CPP]).  Experience gained with the
   Jabber-ID header field within the Jabber instant messaging and
   presence community should provide helpful input to the process of
   defining those more general header fields.

2.  Syntax

   The syntax of the Jabber-ID header field is defined below using
   Augmented Backus-Naur Form (as specified by [ABNF]), where the
   "pathxmpp" rule is defined in [XMPP-URI] and the remaining rules are
   defined in [MESSAGE]:

   "Jabber-ID:" [FWS] pathxmpp [FWS] CRLF

   Note: Although a native XMPP address may contain virtually any
   [UNICODE] character, an electronic mail header may contain only
   printable [US-ASCII] characters (see Section 2 of [MESSAGE]).
   Therefore, any characters outside the US-ASCII range in an XMPP
   address must be converted to US-ASCII before inclusion in a Jabber-ID

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   header field, in accordance with the rules specified in [XMPP-URI].
   In addition, characters allowed in XMPP node identifiers and XMPP
   resource identifiers but disallowed by the relevant URI rules must be
   percent-encoded in accordance with the rules specified in [URI]; for
   details, see [XMPP-URI].

3.  Implementation

3.1.  Inclusion

   The Jabber-ID header field is associated with the author of the
   message; see [MESSAGE].  If the "From:" header field contains more
   than one mailbox, the Jabber-ID header field should not be added to
   the message.  There should be no more than one instance of the
   Jabber-ID header field.

3.2.  Generation

   For a user whose XMPP address is "juliet@example.com", the
   corresponding Jabber-ID header field would be:

   Jabber-ID: juliet@example.com

   As noted, non-US-ASCII characters in XMPP addresses must be converted
   into US-ASCII before inclusion in a Jabber-ID header field.  Consider
   the following XMPP address:


   Note: The string "ř" stands for the Unicode character LATIN
   SMALL LETTER R WITH CARON and the string "č" stands for the
   Unicode character LATIN SMALL LETTER C WITH CARON, following the "XML
   Notation" used in [IRI] to represent characters that cannot be
   rendered in ASCII-only documents (note also that these characters are
   represented in their stringprep canonical form; see [STRINGPREP]).
   For those who do not read Czech, this example could be Anglicized as

   Following the rules in [XMPP-URI] and the Jabber-ID header field
   syntax, the resulting header field would be:


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3.3.  Processing

   Upon receiving an email message containing a Jabber-ID header field,
   a mail user agent (MUA) that supports the field should process the
   field by converting any escaped characters to characters outside the
   US-ASCII range in accordance with the rules specified in [XMPP-URI],
   thus yielding a Jabber Idenfitier that can be used for native
   communication on an XMPP network.

3.4.  Disposition

   A mail user agent (MUA) that has processed a Jabber-ID header field
   may provide appropriate interface elements if it has independent
   information linking the author of the email message with the
   specified Jabber Identifier (e.g., via a user-controlled address book
   or automated directory lookup).  Such interface elements might
   include an indicator of "presence" (i.e., that the author is online
   and available for communication via XMPP) if the user is subscribed
   to the presence of the author, and an element that enables the user
   to initiate a text chat with the author.

4.  IANA Considerations

   In accordance with [REG], the IANA registers the "Jabber-ID" header
   field in the Provisional Message Header Field Registry.  The
   registration template is as follows:

   Header field name:  Jabber-ID
   Applicable protocol:  mail
   Status:  provisional
   Author/Change controller:  XMPP Registrar <mailto:registrar@xmpp.org>
   Specification document(s):  draft-saintandre-jabberid-06 [Note to
      IANA and RFC Editor: Replace I-D name with RFC XXXX, where "XXXX"
      is the number of the RFC that results from this specification, if
   Related information:  For details regarding the native usage and
      format of Jabber Identifiers, see Extensible Messaging and
      Presence Protocol (RFC 3920).

5.  Security Considerations

   Message headers are an existing standard and are designed to easily
   accommodate new types.  Although the Jabber-ID header field may be
   forged, this problem is inherent in Internet email; however, because
   a forged Jabber-ID header field may break automated processing,
   applications should not depend on the Jabber-ID header field to

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   indicate the authenticity of an email message or the identity of its
   author or sender.  Including the Jabber-ID header field among the
   signer header fields in DomainKeys Identified Mail (DKIM) can help to
   mitigate against forging of the header (see [DKIMSIG]).

   Advertising XMPP addresses in email headers may make it easier for
   malicious users to harvest XMPP addresses and therefore to send
   unsolicited bulk communications to the users or applications
   represented by those addresses.  Care should be taken in balancing
   the benefits of open information exchange against the potential costs
   of unwanted communication.  An email user agent that is capable of
   including the Jabber-ID header field in outgoing email messages
   should provide an option for its user to disable inclusion of the
   Jabber-ID header field generally, on a per-recipient basis, and on a
   per-message basis.

   The security considerations discussed in [IRI], [URI], [XMPP-CORE],
   [XMPP-IM], and [XMPP-URI] may also apply to the Jabber-ID message

6.  References

6.1.  Normative References

   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [MESSAGE]  Resnick, P., "Internet Message Format", RFC 2822,
              April 2001.

              Saint-Andre, P., "Internationalized Resource Identifiers
              (IRIs) and Uniform Resource  Identifiers (URIs) for the
              Extensible Messaging and Presence Protocol (XMPP)",
              draft-saintandre-rfc4622bis-01 (work in progress),
              June 2007.

6.2.  Informative References

   [CPIM]     Peterson, J., "Common Profile for Instant Messaging
              (CPIM)", RFC 3860, August 2004.

   [CPP]      Peterson, J., "Common Profile for Presence (CPP)",
              RFC 3859, August 2004.

   [DKIMSIG]  Allman, E., Callas, J., Delany, M., Libbey, M., Fenton,
              J., and M. Thomas, "DomainKeys Identified Mail (DKIM)

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              Signatures", RFC 4871, May 2007.

   [IRI]      Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [REG]      Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004.

              Hoffman, P. and M. Blanchet, "Preparation of
              Internationalized Strings ("stringprep")", RFC 3454,
              December 2002.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard, Version
              3.2.0", 2000.

              The Unicode Standard, Version 3.2.0 is defined by The
              Unicode Standard, Version 3.0 (Reading, MA, Addison-
              Wesley, 2000.  ISBN 0-201-61633-5), as amended by the
              Unicode Standard Annex #27: Unicode 3.1
              (http://www.unicode.org/reports/tr27/) and by the Unicode
              Standard Annex #28: Unicode 3.2

   [URI]      Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

              American National Standards Institute, "Coded Character
              Set - 7-bit American Standard Code for Information
              Interchange", ANSI X3.4, 1986.

              Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

   [XMPP-IM]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Instant Messaging and Presence",
              RFC 3921, October 2004.

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Author's Address

   Peter Saint-Andre
   XMPP Standards Foundation

   URI:   https://stpeter.im/

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