Network Working Group J. Miller
Internet-Draft P. Saint-Andre
Expires: April 23, 2003 Jabber Software Foundation
October 23, 2002
XMPP Instant Messaging
draft-miller-xmpp-im-01
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 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . 7
2.3 Definition of the jabber:iq:register Namespace . . . . . . . 8
2.3.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3. Authentication . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Authentication Using SASL . . . . . . . . . . . . . . . . . 11
3.2 Authentication Using jabber:iq:auth . . . . . . . . . . . . 12
3.3 Definition of the jabber:iq:auth Namespace . . . . . . . . . 13
3.3.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Exchanging Messages . . . . . . . . . . . . . . . . . . . . 15
4.1 Specifying an Intended Recipient . . . . . . . . . . . . . . 15
4.2 Specifying the Sender . . . . . . . . . . . . . . . . . . . 15
4.3 Specifying a Message Type . . . . . . . . . . . . . . . . . 15
4.4 Specifying a Message Subject . . . . . . . . . . . . . . . . 16
4.5 Specifying a Message Thread . . . . . . . . . . . . . . . . 16
4.6 Specifying a Message Body . . . . . . . . . . . . . . . . . 17
4.7 Specifying Additional Information . . . . . . . . . . . . . 17
4.8 Message-Related Errors . . . . . . . . . . . . . . . . . . . 18
5. Exchanging Presence Information . . . . . . . . . . . . . . 19
5.1 Node and Host Responsibilities . . . . . . . . . . . . . . . 19
5.2 Sending Initial Presence . . . . . . . . . . . . . . . . . . 19
5.3 Specifying Availability Status . . . . . . . . . . . . . . . 20
5.4 Specifying Detailed Status Information . . . . . . . . . . . 20
5.5 Probing for Presence . . . . . . . . . . . . . . . . . . . . 20
5.6 Sending Final Presence . . . . . . . . . . . . . . . . . . . 20
6. Managing Subscriptions . . . . . . . . . . . . . . . . . . . 21
6.1 Requesting a Subscription . . . . . . . . . . . . . . . . . 21
6.2 Handling a Subscription Request . . . . . . . . . . . . . . 21
6.3 Cancelling a Subscription from Another Entity . . . . . . . 22
6.4 Unsubscribing from Another Entity's Presence . . . . . . . . 22
7. Managing One's Roster . . . . . . . . . . . . . . . . . . . 23
7.1 Receiving One's Roster on Login . . . . . . . . . . . . . . 23
7.2 Adding a Roster Item . . . . . . . . . . . . . . . . . . . . 23
7.3 Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 24
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7.4 Definition of the jabber:iq:roster Namespace . . . . . . . . 25
7.4.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.4.2 DTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.4.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8. Routing and Delivery Guidelines . . . . . . . . . . . . . . 28
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 29
10. Security Considerations . . . . . . . . . . . . . . . . . . 30
10.1 Secure Identity and Encryption . . . . . . . . . . . . . . . 30
10.2 Node Connections . . . . . . . . . . . . . . . . . . . . . . 30
References . . . . . . . . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 31
Full Copyright Statement . . . . . . . . . . . . . . . . . . 33
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1. Introduction
1.1 Scope
The core features of the XMPP protocol (XMPP Core [2]) 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 2778 [8] and RFC 2779 [9].
Many other functionality areas are defined in the Jabber protocol,
including service discovery, multi-user chat, search, remote
procedure calls, data gathering and forms submission, encryption,
feature negotiation, message composing events, message expiration,
and file transfer; however, such functionality is not described
herein.
1.2 Terminology
This document inherits the terminology defined in XMPP Core [2].
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 roster (a.k.a. contact list)
1.4 Conventions Used in this Document
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 [1].
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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 URI schemes, 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): Host informs node of failed registration:
<iq
type="error"
from="capulet.com"
id="reg_2"/>
<error code="406">Not Acceptable</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>
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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 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:stream/>
element with which it initiated communications with the host.
For the protocol describing how a node authenticates with a host,
refer to XMPP Core [2].
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"/>
<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.
o digest - the concatenation of the stream id and the password,
encrypted according to the SHA1 Secure Hash Algorithm [3] and
represented as all lowercase hex.
o resource - unique value to represent current connection.
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3.3.2 DTD
<!ELEMENT query ((username? | (password | digest)? | resource)*)>
<!ELEMENT username (#PCDATA)>
<!ELEMENT password (#PCDATA)>
<!ELEMENT digest (#PCDATA)>
<!ELEMENT resource (#PCDATA)>
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 the <message/> data
element, a node can send a message to any other node (or, more
generally, any entity).
4.1 Specifying an Intended Recipient
A node MAY 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 the Sender
A node MAY specify the sender's address by including a 'from'
attribute in the message chunk, and MAY specify any resource or full
JID in that 'from' attribute. However, a host MUST verify that the
value of the 'from' attribute matches the node@host/resource of the
connected resource that generated the message chunk. If no 'from'
attribute is included, the host MUST add the valid and authenticated
from address of the connected resource sending the chunk (i.e., the
node@host/resource).
4.3 Specifying a Message Type
As mentioned in XMPP Core [2], 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 no type is set or if the
type is set to a value other than those specified here, the value
SHOULD be defaulted to "normal" by the host. If included, the 'type'
attribute SHOULD have one of the following values:
o normal - A single message
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o chat - A message sent in the context of two-way chat between two
entities
o groupchat - A message sent in the context of multi-user chat among
multiple entities
o headline - A message that represents one of a list of items (e.g.,
in a news feed or information ticker)
o error - A message returned to a sender specifying an error
associated with a previous message sent by the sender to an
intended recipient (for a full list of error messages, see XMPP
Core [2])
4.4 Specifying a Message Subject
A message chunk MAY contain a child element specifying the subject of
the message. The subject MAY 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>
4.5 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 MAY NOT contain mixed content.
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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>
4.6 Specifying a Message Body
A message chunk MAY (and usually will) contain a child element
specifying the body of the message. The body MAY 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/> element other
than the <body/> element.
4.7 Specifying Additional Information
A <message/> element 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. The child element must possess an
'xmlns' namespace declaration (other than those defined for XML
streams) that defines all elements contained within the child
element.
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4.8 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 of type "error" along
with an appropriate error message (for a list of error messages, see
XMPP Core [2]).
A message-related error:
<message
to="juliet@montague.net"
from="romeo@montague.net">
<body>Sleep dwell upon thine eyes</body>
</message>
<message
to="romeo@montague.net"
from="juliet@montague.net"
type="error">
<body>Sleep dwell upon thine eyes</body>
<error code="404">Not Found</error>
</message>
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5. Exchanging Presence Information
Exchanging presence information is made relatively simple within XMPP
by using the <presence/> data element. 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/>
element to the host to express default availability.
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.
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. 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 the <presence/> element.
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 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>
7.2 Adding a Roster Item
At any time, a node MAY add an item to its roster.
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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 element of type "set".
This enables all connected resources to remain in sync with the host-
based roster information.
Host replies with an IQ result to the sending resource and pushes the
updated roster information to all connected resources:
<iq type="result" id="roster_2"/>
<iq type="set" id="roster_3" to="juliet@capulet.com/balcony"/>
<query xmlns="jabber:iq:roster">
<item
name="Nurse"
jid="nurse@capulet.com">
<group>Servants</group>
</item>
</query>
</iq>
<iq type="set" id="roster_3" to="juliet@capulet.com/chamber"/>
<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.
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Node adds a new 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 element 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. IANA Considerations
The IANA registers "jabber-client" and "jabber-server" as GSS-API [7]
service names, as specified in Section 6.1.1.
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10. Security Considerations
For general security considerations, refer to the relevant section of
XMPP Core [2].
10.1 Secure Identity and Encryption
Nodes MAY optionally support signing and encrypting messages and
presence by using the Public Key Infrastructure (e.g., PGP/GnuPG),
with the encrypted or signed data sent in an <x/> element within the
jabber:x:encrypted or jabber:x:signed namespace. (These are
informational protocols approved by the Jabber Software Foundation
and are not covered in this document.)
Implementations MAY choose to offer MIME-based security services
providing message integrity and confidentiality, such as OpenPGP [4]
or S/MIME [5].
10.2 Node Connections
The IP address and method of access of nodes MUST never be made
available by a host, nor are any connections other than the original
host connection required. This helps protect the node's host from
direct attack or identification by third parties.
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References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Miller, J. and P. Saint-Andre, "XMPP Core (draft-miller-jabber-
xmpp-core-00, work in progress)", June 2002.
[3] World Wide Web Consortium, "Secure Hash Algorithm - Version
1.0", October 1997, <http://www.w3.org/PICS/DSig/SHA1_1_0.html>.
[4] Elkins, M., Del Torto, D., Levien, R. and T. Roessler, "MIME
Security with OpenPGP", RFC 3156, August 2001.
[5] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC
2633, June 1999.
[6] Freier, A., Karlton, P. and P. Kocher, "The SSL Protocol -
Version 3.0", November 1996, <http://home.netscape.com/eng/ssl3/
draft302.txt>.
[7] Linn, J., "Generic Security Service Application Program
Interface, Version 2", RFC 2078, January 1997.
[8] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
Instant Messaging", RFC 2778, February 2000, <http://
www.ietf.org/rfc/rfc2778.txt>.
[9] 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>.
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/
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Peter Saint-Andre
Jabber Software Foundation
1899 Wynkoop Street, Suite 600
Denver, CO 80202
US
EMail: stpeter@jabber.org
URI: http://www.jabber.org/
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Full Copyright Statement
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Acknowledgement
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