The IM-ID Header Field
draft-saintandre-header-im-00

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Abstract

This document defines a header field that enables the author of an email message to include an Instant Messaging (IM) URI in the message header block for the purpose of associating the author with an instant messaging address.

Table of Contents

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

1.  Introduction

Several technologies enable entities to exchange messages in close to real time, also known as "instant messaging" or IM [IMP‑REQS] (Day, M., Aggarwal, S., and J. Vincent, “Instant Messaging / Presence Protocol Requirements,” February 2000.). Such technologies include the Extensible Messaging and Presence Protocol [XMPP‑IM] (Saint-Andre, P., “Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence,” October 2004.) and the Session Initiation Protocol [SIP‑IM] (Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and D. Gurle, “Session Initiation Protocol (SIP) Extension for Instant Messaging,” December 2002.). To facilitate the exchange of instant messages, a URI scheme for IM is defined in [CPIM] (Peterson, J., “Common Profile for Instant Messaging (CPIM),” August 2004.).

Because almost all human users of instant messaging systems are users of email systems, it can be helpful for such users to specify their IM URIs in the email messages they author. The IM-ID header field provides a standard location for such information. This document documents the syntax and implementation of the IM-ID header field, including the information necessary to register it in the Permanent Message Header Field Registry maintained by the IANA.

2.  Syntax

The syntax of the IM-ID header field is defined below using Augmented Backus-Naur Form (as specified by [ABNF] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” October 2005.)), where the "IM-URI" rule is defined in [CPIM] (Peterson, J., “Common Profile for Instant Messaging (CPIM),” August 2004.) and the remaining rules are defined in [MESSAGE] (Resnick, P., “Internet Message Format,” April 2001.):

"IM-ID:" [FWS] IM-URI *WSP CRLF

3.  Implementation

3.1.  Inclusion

The IM-ID header field is associated with the author of the message; see [MESSAGE] (Resnick, P., “Internet Message Format,” April 2001.). If the "From:" header field contains more than one mailbox, the IM-ID header field should not be added to the message. There should be no more than one instance of the IM-ID header field.

3.2.  Generation

For a user whose instant messaging URI is "juliet@example.com", the corresponding IM-ID header field would be:

IM-ID: im:juliet@example.com

3.3.  Processing

Upon receiving an email message containing an IM-ID header field, a mail user agent (MUA) that supports the field should process the field by resolving the instant messaging URI in accordance with the procedures specified in [CPIM] (Peterson, J., “Common Profile for Instant Messaging (CPIM),” August 2004.).

3.4.  Disposition

A mail user agent (MUA) that has processed an IM-ID header field may provide appropriate interface elements if it has independent information linking the author of the email message with the specified instant messaging URI (e.g., via a user-controlled address book or automated directory lookup). Such interface elements might include an element that enables the user to initiate a text chat with the author.

4.  IANA Considerations

In accordance with [REG] (Klyne, G., Nottingham, M., and J. Mogul, “Registration Procedures for Message Header Fields,” September 2004.), the IANA registers the "IM-ID" header field in the Permanent Message Header Field Registry. The registration template is as follows:

Header field name:

IM-ID

Applicable protocol:

mail

Status:

permanent

Author/Change controller:

Peter Saint-Andre <mailto:stpeter@jabber.org>

Specification document(s):

draft-saintandre-header-im-00 [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 any]

Related information:

For detail information regarding instant messaging URIs, refer to RFC 3860.

5.  Security Considerations

Message headers are an existing standard and are designed to easily accommodate new types. Although the IM-ID header field may be forged, this problem is inherent in Internet email; however, because a forged IM-ID header field may break automated processing, applications should not depend on the IM-ID header field to indicate the authenticity of an email message or the identity of its author or sender. Including the IM-ID header field among the signer header fields in DomainKeys Identified Mail (DKIM) can help to mitigate against forging of the header (see [DKIMSIG] (Allman, E., Callas, J., Delany, M., Libbey, M., Fenton, J., and M. Thomas, “DomainKeys Identified Mail (DKIM) Signatures,” May 2007.)).

Advertising instant messaging URIs in email headers may make it easier for malicious users to harvest such URIs 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 IM-ID header field in outgoing email messages should provide an option for its user to disable inclusion of the IM-ID header field generally, on a per-recipient basis, and on a per-message basis.

The security considerations discussed in [URI] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) and [CPIM] (Peterson, J., “Common Profile for Instant Messaging (CPIM),” August 2004.) may also apply to the IM-ID message header.

6.  References

6.1. Normative References

6.2. Informative References

Author's Address

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