Network Working GroupP. Saint-Andre
Internet-DraftJabber Software Foundation
Expires: March 11, 2004September 11, 2003


Status of this Memo

This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.

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Copyright Notice

Copyright (C) The Internet Society (2003). All Rights Reserved.


This document defines a URI scheme to address entities that can communicate via the Extensible Messaging and Presence Protocol (XMPP).


Table of Contents


1. Introduction

The Extensible Messaging and Presence Protocol (XMPP)[1] has been adapted by the XMPP WG from the open protocol originally developed by the Jabber community. Currently there exist tens of thousands of servers on the Jabber network, with millions of end users. The addresses of XMPP entities are not specified as full URIs on the network itself, i.e., within the context of the streaming XML technology that forms the foundation of XMPP. However, many applications external to the existing network would like to address XMPP entities as full URIs in compliance with RFC 2396[2].

Many types of applications can be built using XMPP. The best-known such application is instant messaging (IM) and presence as defined in XMPP IM[3]. Therefore it might seem appropriate to use the 'im:' and 'pres:' URI schemes defined in Common Profile for Instant Messaging (CPIM)[4] and Common Profile for Presence (CPP)[5], rather than to define an XMPP-specific URI scheme. Unfortunately, these URI schemes are limited to instant messaging (usually understood as exchanging messages with a single other user) and presence. However, fundamentally XMPP is a technology for near-real-time messaging, presence, and request-response services using streaming XML, rather than only an IM or presence technology. XMPP is already in use in applications quite distinct from IM, including network management, workflow applications, generic publish-subscribe, remote procedure calls, content syndication, gaming, and middleware. These applications require an addressing scheme that is not tied to the particular semantics of the 'im:' and 'pres:' URI schemes. Therefore, this document defines a generic URI scheme that will enable applications to fully address any entity that can communicate via XMPP.

On the XMPP network itself, entities must be addressed as <jid> rather than <xmpp:jid>. However, some interfaces to XMPP services may be provided by non-native applications (e.g., web browsers), and other applications may want to refer to XMPP entities using addresses that are full URIs. The xmpp: URI format is provided for the sake of such interfaces and applications, and MUST NOT be used by native applications for addressing on the XMPP network itself.

An xmpp: URI is opaque rather than hierarchical, and thus is similar to a mailto: URI as defined in RFC 2368[6]. Because an xmpp: URI is opaque, it SHOULD contain only the node identifier (optional) and domain identifier (required) portions of a JID as defined in Section 3 of XMPP Core[1] (including by reference all relevant stringprep profiles). An xmpp: URI MAY include the resource identifier portion of a JID if the XMPP entity must be addressed as such, but this is NOT RECOMMENDED since the delimiter used before a resource identifier in XMPP addresses is the slash character ("/"), which is discouraged by RFC 2396[2] in opaque URIs.

If an xmpp: URI is presented in an interface to an XMPP service (e.g., in a web browser), interacting with such a URI should trigger the application to present a user with an appropriate interface to complete an action such as sending a message, sending presence, managing a subscription, sending an information request (IQ get), or updating relevant information (IQ set).

This memo conforms to the requirements in Registration Procedures for URL Scheme Names[7]. This memo also follows the recommendations in Guidelines for new URL Schemes[8].

1.1 Terminology

This document inherits terminology defined in XMPP Core[1].

The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119[9].

1.2 Discussion Venue

The author welcomes discussion and comments related to the topics presented in this document. The preferred forum is the <> mailing list, for which archives and subscription information are available at <>.

1.3 Intellectual Property Notice

This document is in full compliance with all provisions of Section 10 of RFC 2026. Parts of this specification use the term "jabber" for identifying namespaces and other protocol syntax. Jabber[tm] is a registered trademark of Jabber, Inc. Jabber, Inc. grants permission to the IETF for use of the Jabber trademark in association with this specification and its successors, if any.


2. xmpp: URI IANA Registration

This section provides the information required to register the xmpp: URI scheme.

2.1 URI Scheme Name


2.2 URI Scheme Syntax

The syntax for the xmpp: URI is defined below in Augmented Backus-Naur Form as defined by RFC 2234[10].

XMPP-URI      = "xmpp:" jid [ "/" resource]
jid           = [ node "@" ] host
node          = *( alphanum / escaped /
                "-" / "_" / "." / "!" / "~" / "*" / "(" / ")" )
host          = hostname / IPv4address / IPv6reference
hostname      = *( domainlabel "." ) toplabel [ "." ]
domainlabel   = alphanum / alphanum *( alphanum / "-" ) alphanum
toplabel      = alpha / alpha *( alphanum / "-" ) alphanum
IPv6reference = "[" IPv6address "]"
IPv6address   = hexpart [ ":" IPv4address ]
IPv4address   = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
hexpart       = hexseq / hexseq "::" [ hexseq ] / "::" [ hexseq ]
hexseq        = hex4 *( ":" hex4)
hex4          = 1*4HEXDIG
resource      = *( unreserved / escaped )
reserved      = ";" / "/" / "?" / ":" / "@" / "&" / "=" / "+" /
                "$" / "," / "[" / "]"

2.3 Character Encoding Considerations

Representation of non-ASCII character sets in local-part strings is limited to the standard methods provided as extensions to RFC 2822[11].

2.4 Intended usage

The xmpp: URI is intended to be used by interfaces to the XMPP network from non-native user agents such as web browsers, as well as by non-XMPP applications in order to address XMPP entities as full URIs.

2.5 Security considerations

See Security Considerations of this document.

2.6 Relevant publications

XMPP Core[1], XMPP IM[3]

2.7 Person and email address to contact for further information

Peter Saint-Andre []

2.8 Author/Change controller

This scheme is registered under the IETF tree. As such, the IETF maintains change control.

2.9 Applications and/or protocols which use this URI scheme name

Applications that provide an interface to XMPP services or that need to address XMPP entities as full URIs.


3. IANA Considerations

This entire document addresses IANA considerations.


4. Security Considerations

Detailed security considerations for XMPP are given in XMPP Core[1]. Providing an interface to XMPP services from non-native applications introduces new security concerns. For example, the ability to interact with XMPP entities via a web browser may expose sensitive information to attacks that are not possible or unlikely on a native XMPP network. Due care must be taken in deciding what information is appropriate for representing in xmpp: URIs; in particular, passwords MUST NOT be represented.


Normative References

[1] Saint-Andre, P. and J. Miller, "XMPP Core", draft-ietf-xmpp-core-18 (work in progress), September 2003.
[2] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[3] Saint-Andre, P. and J. Miller, "XMPP Instant Messaging", draft-ietf-xmpp-im-17 (work in progress), September 2003.
[4] Crocker, D. and J. Peterson, "Common Profile for Instant Messaging (CPIM)", draft-ietf-impp-im-03 (work in progress), May 2003.
[5] Crocker, D. and J. Peterson, "Common Profile for Presence (CPP)", draft-ietf-impp-pres-03 (work in progress), May 2003.
[6] Hoffman, P., Masinter, L. and J. Zawinski, "The mailto URL scheme", RFC 2368, July 1998 (TXT, HTML, XML).
[7] Petke, R. and I. King, "Registration Procedures for URL Scheme Names", BCP 35, RFC 2717, November 1999.
[8] Masinter, L., Alvestrand, H., Zigmond, D. and R. Petke, "Guidelines for new URL Schemes", RFC 2718, November 1999.
[9] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[10] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997.
[11] Resnick, P., "Internet Message Format", RFC 2822, April 2001.


Author's Address

  Peter Saint-Andre
  Jabber Software Foundation


Intellectual Property Statement

Full Copyright Statement