Network Working Group P. Saint-Andre
Internet-Draft JSF
Expires: March 29, 2007 September 25, 2006
The Jabber-ID Header Field
draft-saintandre-jabberid-04
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Copyright (C) The Internet Society (2006).
Abstract
This document defines a header field that enables a sender to include
a Jabber Identifier in the header block of an email message for the
purpose of associating the email message or sender with a particular
Extensible Messaging and Presence Protocol (XMPP) address.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Jabber-ID Syntax . . . . . . . . . . . . . . . . . . . . . . . 3
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8
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1. Introduction
The Extensible Messaging and Presence Protocol (XMPP), documented in
[RFC3920], 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
[RFC3921], and XMPP addresses are still referred to as Jabber
Identifiers or Jabber IDs.
Because almost all users of Jabber 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 send.
The Jabber-ID header defined in this document provides a standard
location for that information.
2. Jabber-ID Syntax
The syntax of the Jabber-ID header is defined below using Augmented
Backus-Naur Form (as specified by [RFC4234]), where the "pathxmpp"
rule is defined in [RFC4622] and the remaining rules are defined in
[RFC2822]:
"Jabber-ID:" [FWS] pathxmpp (*WSP / obs-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 [RFC2822]).
Therefore, any non-US-ASCII characters in an XMPP address must be
converted to US-ASCII before inclusion in a Jabber-ID header, in
accordance with the rules specified in [RFC4622].
3. Examples
For a user whose XMPP address is "juliet@example.com", the
corresponding Jabber-ID header 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. Consider the
following XMPP address:
jiři@čechy.example
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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 [RFC3987] to represent characters that cannot be
rendered in ASCII-only documents (note also that these characters are
represented in their stringprep canonical form; see [RFC3454]). For
those who do not read Czech, this example could be Anglicized as
"george@czech-lands.example".
Following the rules in [RFC4622] and the Jabber-ID header syntax, the
resulting header would be:
Jabber-ID: ji%C5%99i@%C4%8Dechy.example
4. IANA Considerations
In accordance with [RFC3864], the IANA registers the "Jabber-ID"
header field in the Permanent Message Header Field Registry. The
registration template is as follows:
Header field name: Jabber-ID
Applicable protocol: mail
Status: standard
Author/Change controller: IETF
Specification document(s): XXXX
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 may be forged,
this problem is inherent in Internet email; however, because a forged
Jabber-ID header may break automated processing, applications should
not depend on the Jabber-ID header to indicate the authenticity of an
email message or the identity of its sender.
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 communications. 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
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Jabber-ID header field generally, on a per-recipient basis, or on a
per-message basis.
6. References
6.1. Normative References
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
[RFC4622] Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)",
RFC 4622, July 2006.
6.2. Informative References
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004.
[RFC3920] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[RFC3921] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence",
RFC 3921, October 2004.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[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
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(http://www.unicode.org/reports/tr28/).
[US-ASCII]
American National Standards Institute, "Coded Character
Set - 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
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Author's Address
Peter Saint-Andre
Jabber Software Foundation
Email: stpeter@jabber.org
URI: xmpp:stpeter@jabber.org
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