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
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all provisions of Section 10 of RFC2026.
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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 <query/>
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:
<iq type="get"
to="capulet.com"
id="reg_1">
<query xmlns="jabber:iq:register"/>
</iq>
Step 2: Host responds with the required registration fields:
<iq type="result"
from="capulet.com"
id="reg_1">
<query xmlns="jabber:iq:register">
<instructions>
Choose a username and password to register with this service.
</instructions>
<email/>
<password/>
<username/>
</query>
</iq>
Note: the node is REQUIRED to provide information for all of the
elements (other than <instructions/>) 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:
<iq type="set"
to="capulet.com"
id="reg_2">
<query xmlns="jabber:iq:register">
<email>juliet@capulet.com</email>
<password>R0m30</password>
<username>juliet</username>
</query>
</iq>
Step 4: Host informs node of successful registration:
<iq
type="result"
from="capulet.com"
id="reg_2"/>
Step 4 (alt 1): Host informs node of failed registration (required
field not provided):
<iq
type="error"
from="capulet.com"
id="reg_2"/>
<query xmlns="jabber:iq:register">
<email>juliet@capulet.com</email>
<password>R0m30</password>
</query>
<error code="406">Not Acceptable</error>
</iq>
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Step 4 (alt 2): Node is already registered:
<iq
type="error"
from="capulet.com"
id="reg_2"/>
<query xmlns="jabber:iq:register">
<registered/>
<email>juliet@capulet.com</email>
<password>R0m30</password>
<username>juliet</username>
</query>
<error code="400">Bad Request</error>
</iq>
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 <remove/> element
as shown below.
Step 1: Node sends request to unregister:
<iq type="set"
to="capulet.com"
id="unreg_1">
<query xmlns="jabber:iq:register">
<remove/>
</query>
</iq>
Step 2: Host informs node of successful unregistration:
<iq
type="result"
from="capulet.com"
id="unreg_1"/>
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
<instructions/>) 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
<!ELEMENT query ((instructions? | username? |
password? | name? | email? | address? |
city? | state? | zip? | phone? | url? |
date? | misc? | text? | remove?)*)>
<!ELEMENT instructions (#PCDATA)>
<!ELEMENT username (#PCDATA)>
<!ELEMENT password (#PCDATA)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT email (#PCDATA)>
<!ELEMENT address (#PCDATA)>
<!ELEMENT city (#PCDATA)>
<!ELEMENT state (#PCDATA)>
<!ELEMENT zip (#PCDATA)>
<!ELEMENT phone (#PCDATA)>
<!ELEMENT url (#PCDATA)>
<!ELEMENT date (#PCDATA)>
<!ELEMENT misc (#PCDATA)>
<!ELEMENT text (#PCDATA)>
<!ELEMENT remove EMPTY>
2.3.3 Schema
<?xml version='1.0' encoding='UTF-8'?>
<xsd:schema
xmlns:xsd='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://www.jabber.org/protocol'
xmlns='http://www.jabber.org/protocol'
elementFormDefault='qualified'>
<xsd:element name='query'>
<xsd:complexType>
<xsd:choice minOccurs='0' maxOccurs='unbounded'>
<xsd:element ref='instructions'/>
<xsd:element ref='username'/>
<xsd:element ref='password'/>
<xsd:element ref='name'/>
<xsd:element ref='email'/>
<xsd:element ref='address'/>
<xsd:element ref='city'/>
<xsd:element ref='state'/>
<xsd:element ref='zip'/>
<xsd:element ref='phone'/>
<xsd:element ref='url'/>
<xsd:element ref='date'/>
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<xsd:element ref='misc'/>
<xsd:element ref='text'/>
<xsd:element ref='remove'/>
</xsd:choice>
</xsd:complexType>
</xsd:element>
<xsd:element name='instructions' type='xsd:string'/>
<xsd:element name='username' type='xsd:string'/>
<xsd:element name='password' type='xsd:string'/>
<xsd:element name='name' type='xsd:string'/>
<xsd:element name='email' type='xsd:string'/>
<xsd:element name='address' type='xsd:string'/>
<xsd:element name='city' type='xsd:string'/>
<xsd:element name='state' type='xsd:string'/>
<xsd:element name='zip' type='xsd:string'/>
<xsd:element name='phone' type='xsd:string'/>
<xsd:element name='url' type='xsd:string'/>
<xsd:element name='date' type='xsd:string'/>
<xsd:element name='misc' type='xsd:string'/>
<xsd:element name='text' type='xsd:string'/>
<xsd:element name='remove'/>
</xsd: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 <stream/> 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:
<iq type="get" id="auth_1">
<query xmlns="jabber:iq:auth">
<username>juliet</username>
</query>
</iq>
Step 2: Host responds with the required fields (in this case, only
the username and resource):
<iq type="result" id="auth_1">
<query xmlns="jabber:iq:auth">
<username>juliet</username>
<resource/>
</query>
</iq>
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Step 3: Node sends resource information:
<iq type="set" id="auth_2">
<query xmlns="jabber:iq:auth">
<username>juliet</username>
<resource>balcony</resource>
</query>
</iq>
Step 4: Host informs node of successful session initiation:
<iq type="result" id="auth_2"/>
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:
<iq type="get" id="auth_1">
<query xmlns="jabber:iq:auth">
<username>juliet</username>
</query>
</iq>
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Step 2: Host responds with the required authentication fields:
<iq type="result" id="auth_1">
<query xmlns="jabber:iq:auth">
<username>juliet</username>
<digest/>
<resource/>
</query>
</iq>
Step 3: Node sends authentication information (encrypted password):
<iq type="set" id="auth_2">
<query xmlns="jabber:iq:auth">
<username>juliet</username>
<digest>64d60e40febe09264c52bc9cbddd5dd1147fae97</digest>
<resource>balcony</resource>
</query>
</iq>
Step 4: Host informs node of successful authentication:
<iq type="result" id="auth_2"/>
Step 4 (alt): Host informs node of failed authentication:
<iq
type="error"
from="capulet.com"
id="auth_2"/>
<query xmlns="jabber:iq:auth">
<username>juliet</username>
<digest>64d60e40febe09264c5wrongpassword2bc9cbddd5dd1147fae97</digest>
<resource>balcony</resource>
</query>
<error code="401">Unauthorized</error>
</iq>
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
<!ELEMENT query ((username? | (password | digest)? | resource)*)>
<!ELEMENT username (#PCDATA)>
<!ELEMENT password (#PCDATA)>
<!ELEMENT digest (#PCDATA)>
<!ELEMENT resource (#PCDATA)>
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3.3.3 Schema
<?xml version='1.0' encoding='UTF-8'?>
<xsd:schema
xmlns:xsd='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://www.jabber.org/protocol'
xmlns='http://www.jabber.org/protocol'
elementFormDefault='qualified'>
<xsd:element name='query'>
<xsd:complexType>
<xsd:choice minOccurs='0' maxOccurs='unbounded'>
<xsd:element ref='username'/>
<xsd:choice minOccurs='0' maxOccurs='1'>
<xsd:element ref='password'/>
<xsd:element ref='digest'/>
</xsd:choice>
<xsd:element ref='resource'/>
</xsd:choice>
</xsd:complexType>
</xsd:element>
<xsd:element name='username' type='xsd:string'/>
<xsd:element name='password' type='xsd:string'/>
<xsd:element name='digest' type='xsd:string'/>
<xsd:element name='resource' type='xsd:string'/>
</xsd: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 <message/>
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 <message/>
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:
<message to="romeo@montague.net" from="juliet@capulet.com/balcony">
<subject>Imploring</subject>
<body>Wherefore art thou, Romeo?</body>
</message>
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 <thread/> 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 <thread/> element MUST have no
attributes and MUST NOT contain mixed content.
A simple threaded conversation:
<message
to="romeo@montague.net/orchard"
from="juliet@capulet.com/balcony"
type="chat">
<body>Art thou not Romeo, and a Montague?</body>
<thread>283461923759234</thread>
</message>
<message
to="juliet@capulet.com/balcony"
from="romeo@montague.net/orchard"
type="chat">
<body>Neither, fair saint, if either thee dislike.</body>
<thread>283461923759234</thread>
</message>
<message
to="romeo@montague.net/orchard"
from="juliet@capulet.com/balcony"
type="chat">
<body>How cam'st thou hither, tell me, and wherefore?</body>
<thread>283461923759234</thread>
</message>
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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
<body/> element.
4.6 Specifying Additional Information
A message chunk MAY house an element containing content that extends
the meaning of the message (e.g., an encrypted form of the message
body). In common usage this child element is often the <x/> element
but MAY be any element, as long as the 'xmlns' namespace declaration
is something other than the streams namespace and the default
namespace; this extended namespace defines all elements contained
within the child element.
4.7 Message-Related Errors
If a message sent by a sender cannot be delivered, a host SHOULD
return that message to the sender in a message chunk of type "error"
along with an appropriate error message (for a list of error
messages, see [1]).
A message-related error:
<message
to="juliet@capulet.com"
from="romeo@montague.net">
<body>Sleep dwell upon thine eyes</body>
</message>
<message
to="romeo@montague.net"
from="juliet@capulet.com"
type="error">
<body>Sleep dwell upon thine eyes</body>
<error code="404">No Such JID</error>
</message>
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5. Exchanging Presence Information
Exchanging presence information is made relatively simple within XMPP
by using presence chunks. However, we see here a contrast to the
handling of messages: although a node MAY send directed presence
information to another entity, in general presence information is
sent from a node to a host and then broadcasted by the host to any
entities that are subscribed to the presence of the sending entity.
5.1 Node and Host Responsibilities
When a node connects to a host, it sends an initial presence chunk to
the host to express default availability. This presence chunk MUST
have no type.
Upon receiving initial presence from a node, the host sends presence
probes to any remote entities that are subscribed to that node's
presence (as represented in the node's roster) in order to determine
if they are available. (The remote host is responsible for
responding to the presence probe only when (1) the probing entity has
been allowed to access the probed entity's presence, e.g., by server
rules or user subscriptions, and (2) the probed entity is available;
the probing entity's host then informs the probing entity of the
probed entity's last known available presence, for all of the probed
entity's resources if applicable.) The host then sends the node's
initial presence chunk to any subscribed entities that are available.
Throughout the active session of a connected resource associated with
the node, the host is responsible for broadcasting any changes in the
availability status of the connected resource to the subscribed
entities that are available, so that such entities are apprised of
availability changes.
Finally, the host MUST notify all of the subscribed and available
entities when a connected resource becomes unavailable.
5.2 Sending Initial Presence
Upon authenticating, a node SHOULD send initial presence to its host
indicating that the connected resource is available for
communications. This presence chunk MUST have no type.
Initial presence sent from node to host:
<presence/>
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5.3 Specifying Availability Status
A node MAY provide further information about its availability status
by using the <show/> element. As defined in [1], the recognized
values for the show element are "away", "chat", "xa", and "dnd".
Availability status:
<presence>
<show>away</show>
</presence>
5.4 Specifying Detailed Status Information
In conjunction with the <show/> element, a node MAY provide detailed
status information by using the <status/> element. The content of
this element is a natural-language description of the node's current
availability status.
Detailed status information:
<presence>
<show>dnd</show>
<status>Busy fighting the Romans</status>
</presence>
5.5 Probing for Presence
A node or a host MAY probe for the current presence of another
entity. A node probing for the presence of another node MUST have
permission to view the presence of the probed node.
Presence probe:
<presence type="probe" to="romeo@montague.net"/>
5.6 Sending Final Presence
Upon ending its session with a host, a node SHOULD send a final
presence chunk that is explicitly of type unavailable.
Sending final presence to express unavailable state:
<presence type="unavailable"/>
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6. Managing Subscriptions
In order to protect the privacy of instant messaging users and any
other entities, presence and availability information is made
available only to other entities that the user has approved. When a
user has agreed that another entity may view its presence, the entity
is said to have a subscription to the user's presence information.
Note well that a subscription lasts across sessions; indeed, it lasts
until the subscriber unsubscribes or the subscribee cancels the
previously-granted subscription. Subscriptions are completed within
XMPP by sending presence chunks containing specially-defined
attributes of presence chunks.
6.1 Requesting a Subscription
A request to subscribe to another entity's presence is made by
sending a presence chunk of type "subscribe".
Sending a subscription request:
<presence
to="juliet@capulet.com"
from="romeo@montague.net"
type="subscribe"/>
6.2 Handling a Subscription Request
When a node receives a subscription request from another entity, it
MAY accept the request by sending a presence chunk of type
"subscribed" or decline the request by sending a presence chunk of
type "unsubscribed".
Accepting a subscription request:
<presence
to="romeo@montague.net"
from="juliet@capulet.com"
type="subscribed"/>
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Denying a presence subscription request:
<presence
to="romeo@montague.net"
from="juliet@capulet.com"
type="unsubscribed"/>
6.3 Cancelling a Subscription from Another Entity
If a node would like to cancel a previously-granted subscription
request, it sends a presence chunk of type "unsubscribed".
Cancelling a previously granted subscription request:
<presence
to="romeo@montague.net"
from="juliet@capulet.com"
type="unsubscribed"/>
6.4 Unsubscribing from Another Entity's Presence
If a node would like to unsubscribe from the presence of another
entity, it sends a presence chunk of type "unsubscribe".
Unsubscribing from an entity's presence:
<presence
to="juliet@capulet.com"
from="romeo@montague.net"
type="unsubscribe"/>
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7. Managing One's Roster
One's list of contacts is called a roster. A roster is stored by the
host so that a user may access roster information from any connected
resource.
7.1 Receiving One's Roster on Login
Upon connecting to the host, a node SHOULD request the roster
(however, because receiving the roster may not be desirable for all
resources, e.g., a connection with limited bandwidth, the node's
request for the roster is OPTIONAL).
Node requests current roster from host:
<iq id="roster_1" type="get">
<query xmlns="jabber:iq:roster"/>
</iq>
Node receives roster from the host:
<iq
from="capulet.com"
to="juliet@capulet.com/balcony"
id="roster_1"
type="result">
<query xmlns="jabber:iq:roster>
<item
jid="romeo@montague.net"
name="Romeo"
subscription="both"/>
<item
jid="mercutio@montague.net"
name="Mercutio"
subscription="both">
<group>Friends</group>
</item>
<item
jid="benvolio@montague.net"
name="Benvolio"
subscription="both">
<group>Friends</group>
</item>
</query>
</iq>
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7.2 Adding a Roster Item
At any time, a node MAY add an item to its roster.
Node adds a new item:
<iq type="set" id="roster_2">
<query xmlns="jabber:iq:roster">
<item
name="Nurse"
jid="nurse@capulet.com">
<group>Servants</group>
</item>
</query>
</iq>
The host is responsible for updating the roster information in
persistent storage, and also for pushing that change out to all
connected resources for the node using an IQ chunk of type "set".
This enables all connected resources to remain in sync with the host-
based roster information.
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Host replies with an IQ result to the sending resource and pushes the
updated roster information to all connected resources:
<iq
from="capulet.com"
to="juliet@capulet.com/balcony"
type="result"
id="roster_2"/>
<iq
from="capulet.com"
to="juliet@capulet.com/balcony"
type="set"
id="roster_3"/>
<query xmlns="jabber:iq:roster">
<item
name="Nurse"
jid="nurse@capulet.com">
<group>Servants</group>
</item>
</query>
</iq>
<iq
from="capulet.com"
to="juliet@capulet.com/chamber"
type="set"
id="roster_3"/>
<query xmlns="jabber:iq:roster">
<item
name="Nurse"
jid="nurse@capulet.com"
subscription="none">
<group>Servants</group>
</item>
</query>
</iq>
7.3 Deleting a Roster Item
At any time, a node MAY delete an item from its roster by doing an IQ
set and making sure that the value of the 'subscription' attribute is
"remove".
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Node removes a item:
<iq type="set" id="roster_2">
<query xmlns="jabber:iq:roster">
<item
name="Nurse"
jid="nurse@capulet.com"
subscription="remove">
<group>Servants</group>
</item>
</query>
</iq>
Note: as with adding a roster item, when deleting a roster item the
host is responsible for updating the roster information in persistent
storage, and also for pushing that change out to all connected
resources for the node using an IQ chunk of type "set".
7.4 Definition of the 'jabber:iq:roster' Namespace
7.4.1 Children
A <query/> element scoped by the 'jabber:iq:roster' namespace MAY
contain zero or more <item/> elements. An item element MAY contain
the following attributes:
o jid - A REQUIRED attribute that contains the complete JID of the
contact that this item represents
o name - An OPTIONAL attribute that contains a natural-language name
for the contact
o subscription - The current status of the subscription related to
this item. Should be one of the following (all other values are
ignored):
* none - no subscription.
* from - this entity has a subscription to the contact.
* to - the contact has a subscription to this entity.
* both - subscription is both to and from.
* remove - item is to be removed.
o ask - An OPTIONAL attribute specifying the current status of a
request to this contact. Should be one of the following (all
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other values are ignored):
* subscribe - this entity is asking to subscribe to that
contact's presence.
* unsubscribe - this entity is asking unsubscribe from that
contact's presence.
An <item/> element MAY contain zero or more instances of the
following element:
o group - Natural-language name of a user-specified group for the
purpose of categorizing contacts into groups.
7.4.2 DTD
<!ELEMENT query ((item)*)>
<!ELEMENT item ((group)*)>
<!ATTLIST item
jid CDATA #REQUIRED
name CDATA #IMPLIED
subscription ( to | from | both | none | remove ) #IMPLIED
ask ( subscribe | unsubscribe ) #IMPLIED
>
<!ELEMENT group (#PCDATA)>
7.4.3 Schema
<?xml version='1.0' encoding='UTF-8'?>
<xsd:schema
xmlns:xsd='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://www.jabber.org/protocol'
xmlns='http://www.jabber.org/protocol'
elementFormDefault='qualified'>
<xsd:element name='query'>
<xsd:complexType>
<xsd:sequence minOccurs='0' maxOccurs='unbounded'>
<xsd:element ref='item'/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name='item'>
<xsd:complexType>
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<xsd:sequence minOccurs='0' maxOccurs='unbounded'>
<xsd:element ref='group'/>
</xsd:sequence>
<xsd:attribute name='jid' type='xsd:string' use='required'/>
<xsd:attribute name='name' type='xsd:string' use='optional'/>
<xsd:attribute name='subscription' use='optional'>
<xsd:simpleType>
<xsd:restriction base='xsd:string'>
<xsd:enumeration value='to'/>
<xsd:enumeration value='from'/>
<xsd:enumeration value='both'/>
<xsd:enumeration value='none'/>
<xsd:enumeration value='remove'/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name='ask' use='optional'>
<xsd:simpleType>
<xsd:restriction base='xsd:string'>
<xsd:enumeration value='subscribe'/>
<xsd:enumeration value='unsubscribe'/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
</xsd:complexType>
</xsd:element>
<xsd:element name='group' type='xsd:string'/>
</xsd:schema>
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8. Routing and Delivery Guidelines
XML chunks that are not handled directly by a host (e.g., for the
purpose of data storage or rebroadcasting) are routed or delivered to
the intended recipient of the chunk as represented by a JID in the
'to' attribute. The following rules apply:
o If the JID contains a resource identifier (to="node@host/
resource"), the chunk is delivered first to the resource that
exactly matches the resource identifier, or secondarily to a
resource that matches partially (e.g., resource "foo" partially
matches resource identifier "foobar").
o If the JID contains a resource identifier and there are no
matching resources, but there are other connected resources
associated with the node, then message chunks are further
processed as if no resource is specified (see next item). For all
other chunks, the host should return them to the sender with a
type of "error" and an appropriate error code (503) and message.
o If the JID contains only a node@host and there is at least one
connected resource available for the node, the host should deliver
the chunk to an appropriate resource based on the availability
state, priority, and connect time of the connected resource(s).
(Existing XMPP implementations contain some hardcoded rules, based
on <priority/> and most recent connection time, for the routing of
such chunks. A more flexible approach to routing would be
desirable.)
o If the JID contains only a node@host and there are no connected
resources available for the node (e.g., an IM user is offline),
the host MAY choose to store the chunk (usually only message and
presence subscription chunks) on behalf of the node and deliver
the chunk when a resource becomes available for that node.
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9. Security Considerations
For security considerations, refer to the relevant section of [1].
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References
[1] Miller, J. and P. Saint-Andre, "XMPP Core (draft-miller-xmpp-
core-02, work in progress)", November 2002.
[2] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for
Presence and Instant Messaging", RFC 2779, February 2000,
<http://www.ietf.org/rfc/rfc2779.txt>.
[3] Jabber Software Foundation, "Jabber Software Foundation", August
2001, <http://www.jabber.org/>.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[5] World Wide Web Consortium, "Secure Hash Algorithm - Version
1.0", October 1997, <http://www.w3.org/PICS/DSig/SHA1_1_0.html>.
Authors' Addresses
Jeremie Miller
Jabber Software Foundation
1899 Wynkoop Street, Suite 600
Denver, CO 80202
US
EMail: jeremie@jabber.org
URI: http://www.jabber.org/people/jer.php
Peter Saint-Andre
Jabber Software Foundation
1899 Wynkoop Street, Suite 600
Denver, CO 80202
US
EMail: stpeter@jabber.org
URI: http://www.jabber.org/people/stpeter.php
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Full Copyright Statement
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Acknowledgement
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