Network Working Group P. Saint-Andre Internet-Draft XMPP Standards Foundation Intended status: Informational November 5, 2007 Expires: May 8, 2008 The Presence-ID Header Field draft-saintandre-header-pres-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 8, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document defines a header field that enables the author of an email message to include a Presence URI in the message header block for the purpose of associating the author with an address that provides information about network availability, also known as "presence". Saint-Andre Expires May 8, 2008 [Page 1] Internet-Draft Presence-ID November 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Implementation . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Inclusion . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Generation . . . . . . . . . . . . . . . . . . . . . . . . 3 3.3. Processing . . . . . . . . . . . . . . . . . . . . . . . . 4 3.4. Disposition . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5 6.2. Informative References . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Saint-Andre Expires May 8, 2008 [Page 2] Internet-Draft Presence-ID November 2007 1. Introduction Several technologies enable entities to share information about their network availability, also known as "presence" [IMP-REQS]. Such technologies include the Extensible Messaging and Presence Protocol [XMPP-IM] and the Session Initiation Protocol [SIP-PRES]. To facilitate the exchange of presence information, a URI scheme for presence is defined in [CPP]. Because almost all human users of presence systems are users of email systems, it can be helpful for such users to specify their presence URIs in the email messages they author. The Presence-ID header field provides a standard location for such information. This document documents the syntax and implementation of the Presence-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 Presence-ID header field is defined below using Augmented Backus-Naur Form (as specified by [ABNF]), where the "PRES- URI" rule is defined in [CPP] and the remaining rules are defined in [MESSAGE]: "Presence-ID:" [FWS] PRES-URI *WSP CRLF 3. Implementation 3.1. Inclusion The Presence-ID header field is associated with the author of the message; see [MESSAGE]. If the "From:" header field contains more than one mailbox, the Presence-ID header field should not be added to the message. There should be no more than one instance of the Presence-ID header field. 3.2. Generation For a user whose presence URI is "juliet@example.com", the corresponding Presence-ID header field would be: Presence-ID: pres:juliet@example.com Saint-Andre Expires May 8, 2008 [Page 3] Internet-Draft Presence-ID November 2007 3.3. Processing Upon receiving an email message containing a Presence-ID header field, a mail user agent (MUA) that supports the field should process the field by resolving the presence URI in accordance with the procedures specified in [CPP]. 3.4. Disposition A mail user agent (MUA) that has processed a Presence-ID header field may provide appropriate interface elements if it has independent information linking the author of the email message with the specified presence URI (e.g., via a user-controlled address book or automated directory lookup). If the user is subscribed to the presence of the author, such interface elements might include an indicator that the author is online and available for communication over a network. 4. IANA Considerations In accordance with [REG], the IANA registers the "Presence-ID" header field in the Permanent Message Header Field Registry. The registration template is as follows: Header field name: Presence-ID Applicable protocol: mail Status: permanent Author/Change controller: Peter Saint-Andre Specification document(s): draft-saintandre-header-pres-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 presence URIs, refer to RFC 3859. 5. Security Considerations Message headers are an existing standard and are designed to easily accommodate new types. Although the Presence-ID header field may be forged, this problem is inherent in Internet email; however, because a forged Presence-ID header field may break automated processing, applications should not depend on the Presence-ID header field to indicate the authenticity of an email message or the identity of its author or sender. Including the Presence-ID header field among the signer header fields in DomainKeys Identified Mail (DKIM) can help to Saint-Andre Expires May 8, 2008 [Page 4] Internet-Draft Presence-ID November 2007 mitigate against forging of the header (see [DKIMSIG]). Advertising presence 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 Presence-ID header field in outgoing email messages should provide an option for its user to disable inclusion of the Presence-ID header field generally, on a per-recipient basis, and on a per-message basis. The security considerations discussed in [URI] and [CPP] may also apply to the Presence-ID message header. 6. References 6.1. Normative References [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 4234, October 2005. [CPP] Peterson, J., "Common Profile for Presence (CPP)", RFC 3859, August 2004. [MESSAGE] Resnick, P., "Internet Message Format", RFC 2822, April 2001. 6.2. Informative References [DKIMSIG] Allman, E., Callas, J., Delany, M., Libbey, M., Fenton, J., and M. Thomas, "DomainKeys Identified Mail (DKIM) Signatures", RFC 4871, May 2007. [IMP-REQS] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging / Presence Protocol Requirements", RFC 2779, February 2000. [REG] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004. [SIP-PRES] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004. Saint-Andre Expires May 8, 2008 [Page 5] Internet-Draft Presence-ID November 2007 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence", RFC 3921, October 2004. Author's Address Peter Saint-Andre XMPP Standards Foundation Email: stpeter@jabber.org URI: https://stpeter.im/ Saint-Andre Expires May 8, 2008 [Page 6] Internet-Draft Presence-ID November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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