XMPP Instant Messaging
From: http://www.jabber.org/ietf/draft-miller-xmpp-im-02.txt
Reference: draft-miller-xmpp-im-02
------------------------------------------------------------------------
Network Working Group J. Miller
Internet-Draft P. Saint-Andre
Expires: May 4, 2003 Jabber Software Foundation
November 03, 2002
XMPP Instant Messaging
draft-miller-xmpp-im-02
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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This Internet-Draft will expire on May 4, 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document describes the specific extensions to and applications
of the eXtensible Messaging and Presence Protocol (XMPP) that are
necessary to create a basic instant messaging and presence
application (specificlaly, an application that is compatible with the
open-source Jabber instant messaging system).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Conventions Used in this Document . . . . . . . . . . . . . 4
1.5 Discussion Venue . . . . . . . . . . . . . . . . . . . . . . 5
1.6 Intellectual Property Notice . . . . . . . . . . . . . . . . 5
2. Registration . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Registration Data Flow . . . . . . . . . . . . . . . . . . . 6
2.2 Cancellation Data Flow . . . . . . . . . . . . . . . . . . . 8
2.3 Definition of the 'jabber:iq:register' Namespace . . . . . . 8
2.3.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3. Authentication . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Authentication Using SASL . . . . . . . . . . . . . . . . . 12
3.2 Authentication Using' jabber:iq:auth . . . . . . . . . . . . 13
3.3 Definition of the 'jabber:iq:auth' Namespace . . . . . . . . 14
3.3.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4. Exchanging Messages . . . . . . . . . . . . . . . . . . . . 17
4.1 Specifying an Intended Recipient . . . . . . . . . . . . . . 17
4.2 Specifying a Message Type . . . . . . . . . . . . . . . . . 17
4.3 Specifying a Message Subject . . . . . . . . . . . . . . . . 18
4.4 Specifying a Message Thread . . . . . . . . . . . . . . . . 18
4.5 Specifying a Message Body . . . . . . . . . . . . . . . . . 19
4.6 Specifying Additional Information . . . . . . . . . . . . . 19
4.7 Message-Related Errors . . . . . . . . . . . . . . . . . . . 19
5. Exchanging Presence Information . . . . . . . . . . . . . . 20
5.1 Node and Host Responsibilities . . . . . . . . . . . . . . . 20
5.2 Sending Initial Presence . . . . . . . . . . . . . . . . . . 20
5.3 Specifying Availability Status . . . . . . . . . . . . . . . 21
5.4 Specifying Detailed Status Information . . . . . . . . . . . 21
5.5 Probing for Presence . . . . . . . . . . . . . . . . . . . . 21
5.6 Sending Final Presence . . . . . . . . . . . . . . . . . . . 21
6. Managing Subscriptions . . . . . . . . . . . . . . . . . . . 22
6.1 Requesting a Subscription . . . . . . . . . . . . . . . . . 22
6.2 Handling a Subscription Request . . . . . . . . . . . . . . 22
6.3 Cancelling a Subscription from Another Entity . . . . . . . 23
6.4 Unsubscribing from Another Entity's Presence . . . . . . . . 23
7. Managing One's Roster . . . . . . . . . . . . . . . . . . . 24
7.1 Receiving One's Roster on Login . . . . . . . . . . . . . . 24
7.2 Adding a Roster Item . . . . . . . . . . . . . . . . . . . . 25
7.3 Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 26
7.4 Definition of the 'jabber:iq:roster' Namespace . . . . . . . 27
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7.4.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.4.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.4.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8. Routing and Delivery Guidelines . . . . . . . . . . . . . . 30
9. Security Considerations . . . . . . . . . . . . . . . . . . 31
References . . . . . . . . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 32
Full Copyright Statement . . . . . . . . . . . . . . . . . . 33
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1. Introduction
1.1 Overview
The core features of the XMPP protocol are defined in XMPP Core [1].
These features, specifically XML streams as well as the
'jabber:client' and 'jabber:server' namespaces, provide the building
blocks for many types of near-real-time applications, which may be
layered on top of the core by sending XML chunks that are scoped by
specific XML namespaces. This document describes the specific
extensions to and applications of XMPP Core that are used to create
the basic functionality expected of an instant messaging and presence
application as defined in RFC 2779 [2]. Extended namespaces for many
other functionality areas have been defined and continue to be
defined by the Jabber Software Foundation [3], including service
discovery, multi-user chat, search, remote procedure calls, data
gathering and forms submission, encryption, feature negotiation,
message composing events, message expiration, delayed delivery, and
file transfer; however, such functionality is not described herein
because it is not required by [2].
1.2 Terminology
This document inherits the terminology defined in [1].
1.3 Requirements
For the purposes of this document, we stipulate that a basic instant
messaging and presence application needs to enable a node to perform
the following functionality:
o Register an account with a host
o Authenticate with a host
o Exchange messages with other nodes
o Exchange presence information with other nodes
o Manage subscriptions to and from other nodes
o Manage the items in the node's contact list (called a "roster")
1.4 Conventions Used in this Document
The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
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"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [4].
1.5 Discussion Venue
The authors welcome discussion and comments related to the topics
presented in this document, preferably on the "xmppwg@jabber.org"
mailing list (archives and subscription information are available at
http://www.jabber.org/cgi-bin/mailman/listinfo/xmppwg/).
1.6 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 Jabber trademark in association with this
specification and its successors, if any.
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2. Registration
Registering with a host is necessary in order for a node to engage in
any desired functionality. Certainly such registration MAY (and
frequently does) occur outside the context of an instant messaging
and presence application. However, XMPP also enables a node to
register with a host within the context of an IM system. This
functionality is enabled by sending and receiving IQ chunks in a
request-response pattern, where the IQ chunks contain
elements in the 'jabber:iq:register' namespace.
2.1 Registration Data Flow
Step 1: Node queries host regarding information that is required in
order to register:
Step 2: Host responds with the required registration fields:
Choose a username and password to register with this service.
Note: the node is REQUIRED to provide information for all of the
elements (other than ) contained in the IQ result.
(Note also that the XML chunk shown above does not include a 'to'
attribute, since the connected socket does not yet have an account.)
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Step 3: Node provides required information:
juliet@capulet.com
R0m30
juliet
Step 4: Host informs node of successful registration:
Step 4 (alt 1): Host informs node of failed registration (required
field not provided):
juliet@capulet.com
R0m30
Not Acceptable
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Step 4 (alt 2): Node is already registered:
juliet@capulet.com
R0m30
juliet
Bad Request
2.2 Cancellation Data Flow
The 'jabber:iq:register' namespace also makes it possible for a user
to cancel a registration with a host by sending a element
as shown below.
Step 1: Node sends request to unregister:
Step 2: Host informs node of successful unregistration:
2.3 Definition of the 'jabber:iq:register' Namespace
2.3.1 Children
While numerous fields are available for use in the
'jabber:iq:register' namespace, only those fields (other than
) sent from the host in an IQ result are REQUIRED in
order to register. The officially-recognized fields available for
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use are as follows:
o instructions
o username
o password
o name
o email
o address
o city
o state
o zip
o phone
o url
o date
o misc
o text
o remove - request to unregister (sent only in an IQ set)
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2.3.2 DTD
2.3.3 Schema
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3. Authentication
In order to gain access to the network of XMPP-compliant applications
and thus engage in standard IM functionality such as exchanging
messages and presence, a node must authenticate with a host. The
preferred authentication method is SASL. Authentication using the
older 'jabber:iq:auth' method is OPTIONAL and MAY be used if a node
does not support SASL.
3.1 Authentication Using SASL
If a node is capable of authenticating with SASL, it MUST include the
agreed-upon SASL namespace within the opening element with
which it initiated communications with the host.
For the protocol describing how a node authenticates with a host,
refer to [1].
Once a node has authenticated its streams with a host, it MUST
provide a resource associated with the connection. This is
accomplished by means of the 'jabber:iq:auth' namespace. The
protocol for doing so is described below.
Step 1: Node queries host regarding information that is still
required to begin a session:
juliet
Step 2: Host responds with the required fields (in this case, only
the username and resource):
juliet
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Step 3: Node sends resource information:
juliet
balcony
Step 4: Host informs node of successful session initiation:
3.2 Authentication Using' jabber:iq:auth
Earlier iterations of XMPP contained a client-server authentication
protocol that was enforced after the stream was negotiated; this
protocol, which uses the 'jabber:iq:auth' namespace, is described for
completeness in this section.
The 'jabber:iq:auth' namespace provides two things: (1) a simple way
for a node to authenticate with a host and (2) a way to create a
resource representing a specific connection or session associated
with the node.
The following is the data flow for a complete example of a node
authenticating with a host.
Step 1: Node queries host regarding information that is required in
order to authenticate:
juliet
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Step 2: Host responds with the required authentication fields:
juliet
Step 3: Node sends authentication information (encrypted password):
juliet
64d60e40febe09264c52bc9cbddd5dd1147fae97
balcony
Step 4: Host informs node of successful authentication:
Step 4 (alt): Host informs node of failed authentication:
juliet
64d60e40febe09264c5wrongpassword2bc9cbddd5dd1147fae97
balcony
Unauthorized
3.3 Definition of the 'jabber:iq:auth' Namespace
3.3.1 Children
o username - the unique username for this node (usually an IM user).
o password - the secret key or passphrase for the node's access to
the host.
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o digest - the concatenation of the stream id and the password,
encrypted according to the SHA1 Secure Hash Algorithm [5] and
represented as all lowercase hex.
o resource - unique value to represent current connection.
3.3.2 DTD
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3.3.3 Schema
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4. Exchanging Messages
Exchanging messages is simple within XMPP: using a message chunk, a
node can send a message to any other node (or, more generally, any
entity).
4.1 Specifying an Intended Recipient
A node SHOULD specify an intended recipient for the message by
providing an appropriate JID in the 'to' attribute of the
element. Normally, the value of the 'to' attribute specifies an
entity other than the sending node (for exceptions, see the next
paragraph). The intended recipient MAY be any valid JID (e.g., a
node on the same host, a node on a different host, the host itself,
or another host).
If no 'to' address is specified, it is implied that the message is
addressed to the sending node itself (i.e., the node@host sending the
chunk); furthermore, a message explicitly or implicitly addressed to
the sending node itself is processed by the host on behalf of that
node. A message addressed to a specific connected resource
associated with the sending node is delivered to that node@host/
resource (which MAY be different from the connected resource that
generated the message).
4.2 Specifying a Message Type
As mentioned in [1], there are several defined types of messages
(specified by means of a 'type' attribute within the
element). In the context of an instant messaging application, a node
MAY include a message type in order to capture the conversational
context of the message, thus providing a hint regarding presentation
(e.g., in a GUI). If included, the 'type' attribute SHOULD have one
of the following values (any other value MAY be ignored):
o chat -- The message is sent in the context of a one-to-one chat
conversation.
o groupchat -- The message is sent in the context of a multi-user
chat environment.
o headline -- The message is generated by an automated service that
delivers content (news, sports, market information, etc.).
o error - A message returned to a sender specifying an error
associated with a previous message sent by the sender (for a full
list of error messages, see [1])
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4.3 Specifying a Message Subject
A message chunk MAY contain a child element specifying the subject of
the message. The subject MUST NOT contain mixed content.
A message with a subject:
Imploring
Wherefore art thou, Romeo?
4.4 Specifying a Message Thread
A message chunk MAY contain a child element specifying the thread of
the message for the purpose of tracking a conversation thread. The
content of the element is a random string that is generated
by the sender; this string MAY be copied back to the sender in
subsequent replies. If included, the element MUST have no
attributes and MUST NOT contain mixed content.
A simple threaded conversation:
Art thou not Romeo, and a Montague?
283461923759234
Neither, fair saint, if either thee dislike.
283461923759234
How cam'st thou hither, tell me, and wherefore?
283461923759234
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4.5 Specifying a Message Body
A message chunk MAY (and usually will) contain a child element
specifying the body of the message. The body MUST NOT contain mixed
content. If it is necessary to provide the message body in an
alternate form (e.g., encrypted using the public key infrastructure
or formatted using XHTML), the alternate form SHOULD be contained in
an appropriately-namespaced child of the message chunk other than the