Network Working Group P. Saint-Andre
Internet-Draft J. Miller
Expires: December 3, 2003 Jabber Software Foundation
June 04, 2003
XMPP Instant Messaging
draft-ietf-xmpp-im-12
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 December 3, 2003.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document describes specific extensions to and applications of
the Extensible Messaging and Presence Protocol (XMPP) that provide
the basic instant messaging and presence functionality defined in RFC
2779.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Discussion Venue . . . . . . . . . . . . . . . . . . . . . . 5
1.5 Intellectual Property Notice . . . . . . . . . . . . . . . . 5
2. Establishing a Session . . . . . . . . . . . . . . . . . . . 6
3. Exchanging Messages . . . . . . . . . . . . . . . . . . . . 8
3.1 Specifying an Intended Recipient . . . . . . . . . . . . . . 8
3.2 Specifying a Message Type . . . . . . . . . . . . . . . . . 8
3.3 Specifying a Message Body . . . . . . . . . . . . . . . . . 9
3.4 Specifying a Message Subject . . . . . . . . . . . . . . . . 10
3.5 Specifying a Conversation Thread . . . . . . . . . . . . . . 10
4. Exchanging Presence Information . . . . . . . . . . . . . . 12
4.1 Client and Server Responsibilities . . . . . . . . . . . . . 12
4.2 Specifying Availability Status . . . . . . . . . . . . . . . 14
4.3 Specifying Detailed Status Information . . . . . . . . . . . 15
4.4 Specifying Presence Priority . . . . . . . . . . . . . . . . 15
4.5 Determining When a Contact Went Offline . . . . . . . . . . 16
4.6 Presence Examples . . . . . . . . . . . . . . . . . . . . . 17
5. Managing Subscriptions . . . . . . . . . . . . . . . . . . . 22
5.1 Requesting a Subscription . . . . . . . . . . . . . . . . . 22
5.2 Handling a Subscription Request . . . . . . . . . . . . . . 22
5.3 Cancelling a Subscription from Another Entity . . . . . . . 23
5.4 Unsubscribing from Another Entity's Presence . . . . . . . . 23
6. Managing One's Roster . . . . . . . . . . . . . . . . . . . 24
6.1 Retrieving One's Roster on Login . . . . . . . . . . . . . . 24
6.2 Adding a Roster Item . . . . . . . . . . . . . . . . . . . . 25
6.3 Updating a Roster Item . . . . . . . . . . . . . . . . . . . 26
6.4 Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 27
7. Integration of Roster Items and Presence Subscriptions . . . 28
7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.2 User Subscribes to Contact . . . . . . . . . . . . . . . . . 28
7.2.1 Alternate Flow: Contact Declines Subscription Request . . . 32
7.3 Creating a Mutual Subscription . . . . . . . . . . . . . . . 33
7.3.1 Alternate Flow: User Declines Subscription Request . . . . . 36
7.4 Unsubscribing . . . . . . . . . . . . . . . . . . . . . . . 37
7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual . . . 38
7.4.2 Case #2: Unsubscribing When Subscription is Mutual . . . . . 39
7.5 Cancelling a Subscription . . . . . . . . . . . . . . . . . 42
7.5.1 Case #1: Cancelling When Subscription is Not Mutual . . . . 42
7.5.2 Case #2: Cancelling When Subscription is Mutual . . . . . . 44
7.6 Removing a Roster Item and Cancelling All Subscriptions . . 46
8. Blocking Communication . . . . . . . . . . . . . . . . . . . 49
8.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.2 Business Rules . . . . . . . . . . . . . . . . . . . . . . . 51
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8.3 Retrieving One's Privacy Lists . . . . . . . . . . . . . . . 52
8.4 Managing Active Lists . . . . . . . . . . . . . . . . . . . 55
8.5 Managing the Default List . . . . . . . . . . . . . . . . . 56
8.6 Editing a Privacy List . . . . . . . . . . . . . . . . . . . 57
8.7 Adding a New Privacy List . . . . . . . . . . . . . . . . . 58
8.8 Removing a Privacy List . . . . . . . . . . . . . . . . . . 58
8.9 Blocking Messages . . . . . . . . . . . . . . . . . . . . . 59
8.10 Blocking Inbound Presence Notifications . . . . . . . . . . 60
8.11 Blocking Outbound Presence Notifications . . . . . . . . . . 62
8.12 Blocking IQs . . . . . . . . . . . . . . . . . . . . . . . . 64
8.13 Blocking All Communication . . . . . . . . . . . . . . . . . 65
8.14 Blocked Entity Attempts to Communicate with User . . . . . . 67
8.15 Higher-Level Heuristics . . . . . . . . . . . . . . . . . . 68
9. Server Rules for Handling XML Stanzas . . . . . . . . . . . 70
9.1 No 'to' Address . . . . . . . . . . . . . . . . . . . . . . 70
9.2 Foreign Domain . . . . . . . . . . . . . . . . . . . . . . . 70
9.3 Subdomain . . . . . . . . . . . . . . . . . . . . . . . . . 70
9.4 Bare Domain or Specific Resource . . . . . . . . . . . . . . 70
9.5 User in Same Domain . . . . . . . . . . . . . . . . . . . . 71
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 73
10.1 XML Namespace Name for Session Data . . . . . . . . . . . . 73
11. Security Considerations . . . . . . . . . . . . . . . . . . 74
Normative References . . . . . . . . . . . . . . . . . . . . 75
Informative References . . . . . . . . . . . . . . . . . . . 76
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 76
A. vCards . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
B. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 78
B.1 session . . . . . . . . . . . . . . . . . . . . . . . . . . 78
B.2 jabber:iq:last . . . . . . . . . . . . . . . . . . . . . . . 78
B.3 jabber:iq:privacy . . . . . . . . . . . . . . . . . . . . . 78
B.4 jabber:iq:roster . . . . . . . . . . . . . . . . . . . . . . 81
C. Revision History . . . . . . . . . . . . . . . . . . . . . . 83
C.1 Changes from draft-ietf-xmpp-im-11 . . . . . . . . . . . . . 83
C.2 Changes from draft-ietf-xmpp-im-10 . . . . . . . . . . . . . 83
C.3 Changes from draft-ietf-xmpp-im-09 . . . . . . . . . . . . . 83
C.4 Changes from draft-ietf-xmpp-im-08 . . . . . . . . . . . . . 84
C.5 Changes from draft-ietf-xmpp-im-07 . . . . . . . . . . . . . 84
C.6 Changes from draft-ietf-xmpp-im-06 . . . . . . . . . . . . . 84
C.7 Changes from draft-ietf-xmpp-im-05 . . . . . . . . . . . . . 84
C.8 Changes from draft-ietf-xmpp-im-04 . . . . . . . . . . . . . 85
C.9 Changes from draft-ietf-xmpp-im-03 . . . . . . . . . . . . . 85
C.10 Changes from draft-ietf-xmpp-im-02 . . . . . . . . . . . . . 85
C.11 Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . . . 85
C.12 Changes from draft-ietf-xmpp-im-00 . . . . . . . . . . . . . 85
C.13 Changes from draft-miller-xmpp-im-02 . . . . . . . . . . . . 86
Intellectual Property and Copyright Statements . . . . . . . 87
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1. Introduction
1.1 Overview
The core features of the Extensible Messaging and Presence Protocol
are defined in XMPP Core [1]. These features -- specifically XML
streams, stream authentication and encryption, and the ,
, and children of the stream root -- provide the
building blocks for many types of near-real-time applications, which
may be layered on top of the core by sending application-specific
data qualified by particular XML namespaces. This document describes
extensions to and applications of XMPP Core that provide the basic
functionality expected of an instant messaging (IM) and presence
application as defined in RFC 2779 [2].
1.2 Requirements
For the purposes of this document, the requirements of a basic
instant messaging and presence application are defined by RFC 2779
[2]. At a high level, RFC 2779 stipulates that a user must be able to
complete the following use cases:
o Exchange messages with other users
o Exchange presence information with other users
o Manage subscriptions to and from other users
o Manage items in a contact list (in XMPP this is called a "roster")
o Block communications to or from specific other users
Detailed definitions of these functionality areas are contained in
RFC 2779, and the interested reader is directed to that document
regarding the requirements addressed herein.
Note: while XMPP-based instant messaging and presence meets the
requirements of RFC 2779, it was not designed explicitly with RFC
2779 in mind, since the base protocol evolved through an open
development process within the Jabber open-source community before
RFC 2779 was written. Note also that although protocols addressing
many other functionality areas have been defined in the Jabber
community, such protocols are not included in this document because
they are not required by RFC 2779 [2].
1.3 Terminology
This document inherits the terminology defined in XMPP Core [1].
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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 [3].
1.4 Discussion Venue
The authors welcome 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 .
1.5 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.
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2. Establishing a Session
Most instant messaging and presence applications based on XMPP are
implemented via a client-server architecture that requires a user to
establish a session on a server in order to engage in the expected
instant messaging and presence activities. However, there are several
pre-conditions that must be met before a user may establish such a
session. These include:
1. Account Provisioning -- methods for account provisioning include
account creation by a server administrator as well as in-band
account registration using the 'jabber:iq:register' namespace;
the latter method is documented by the Jabber Software Foundation
[4] at but is out of scope for
this document.
2. Authentication and Resource Authorization -- methods for
completing these pre-conditions are documented in XMPP Core [1];
note that client authentication with a server MUST include an
authorization identity that specifies the full JID () associated with the connection for addressing
purposes.
Once a client has authenticated with a server and has authorized a
full JID, it SHOULD request that the server activate an instant
messaging session for the client. This is accomplished by means of
the 'urn:ietf:params:xml:ns:xmpp-session' namespace:
Step 1: Client requests session with server:
Step 2: Server informs client that session has been created:
Several error conditions are possible. For example, the server may
encounter an internal condition that prevents it from creating the
session, the username or authorization identity may lack permissions
to create a session, or there may already be an active session
associated with an authzid of the same name.
If the server encounters an internal condition that prevents it from
creating the session, it MUST return an error.
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Step 2 (alt): Server responds with error (internal server error):
If the username or authorization identity is not allowed to create a
session, the server MUST return an error.
Step 2 (alt): Server responds with error (username or authzid not
allowed to create session):
If there is already an active session associated with an authzid of
the same name, the server MUST either (1) terminate the active
session and allow the newly-requested session, or (2) disallow the
newly-requested session and maintain the existing session. Which of
these the server does is up to the implementation, although it is
RECOMMENDED to implement (1).
Step 2 (alt): Server informs client of resource conflict (the desired
resource name is already in use by another active connection):
After establishing a session, a client SHOULD send initial presence
and request its roster as described below, although these actions are
NOT REQUIRED.
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3. Exchanging Messages
Exchanging messages is a basic use of XMPP and is effected when a
user generates a message stanza that is addressed to another user
(or, more generally, another entity). As defined under Section 9, the
sender's server is responsible for delivering the message to the
intended recipient (if the recipient is on the same server) or for
routing the message to the recipient's server (if the recipient is on
a different server).
For information regarding the syntax of message stanzas as well as
their defined attributes and child elements, refer to XMPP Core [1].
3.1 Specifying an Intended Recipient
An instant messaging client SHOULD specify an intended recipient for
a message by providing the JID of an entity other than the sender in
the 'to' attribute of the stanza. If the message is being
sent in reply to a message previously received from an address of the
form (e.g., within the context of a chat
session), the value of the 'to' address SHOULD be the full JID
() rather than merely unless the
sender has knowledge (via presence) that the intended recipient's
resource is no longer available. If the message is being sent outside
the context of any existing chat session or received message, the
value of the 'to' address SHOULD be of the form rather
than .
3.2 Specifying a Message Type
As mentioned in XMPP Core [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 client SHOULD 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 the 'type' attribute
is included, it 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. A compliant client SHOULD present an interface
enabling one-to-one chat between the two parties, including an
appropriate conversation history.
o error -- An error has occurred related to a previous message sent
by the sender (for details regarding stanza error syntax, see XMPP
Core [1]). A compliant client SHOULD present an appropriate
interface informing the sender of the nature of the error.
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o groupchat -- The message is sent in the context of a multi-user
chat environment. A compliant client SHOULD present an interface
enabling many-to-many chat between the parties, including a roster
of parties in the chatroom and an appropriate conversation
history.
o headline -- The message is probably generated by an automated
service that delivers or broadcasts content (news, sports, market
information, RSS feeds, etc.). No reply to the message is
expected, and a compliant client SHOULD present an interface that
appropriately differentiates the message from standalone messages,
chat sessions, or groupchat sessions (e.g., by not providing the
recipient with the ability to reply).
o normal -- The message is a standalone message to which the
recipient MAY reply if desired. This is the default type; if no
'type' attribute is provided, or if the value of the 'type'
attribute is other than one of the values specified, an
application SHOULD consider the message to be of type "normal".
Although the 'type' attribute is NOT REQUIRED, it is considered
polite to mirror the type in any replies to a message; furthermore,
some specialized applications (e.g., a multi-user chat service) MAY
at their discretion enforce the use of a particular message type
(e.g., type='groupchat').
3.3 Specifying a Message Body
A message stanza MAY (and often will) contain a child element
specifying the primary meaning of the message. The content of the
body element MUST be XML character data and the element MUST NOT
contain mixed content. If it is necessary to provide the primary
meaning in an alternate form (e.g., formatted using XHTML), the
alternate form MUST be contained in some other child of the message
stanza. However, multiple elements MAY be included to provide
the primary meaning in different languages, as long as each such
element possesses an 'xml:lang' attribute with a distinct value.
Example: A message with a body:
Wherefore art thou, Romeo?
PročeŽ jsi ty, Romeo?
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3.4 Specifying a Message Subject
A message stanza MAY contain one or more child elements
specifying the topic of the message. The content of the subject
element MUST be XML character data and the element MUST NOT contain
mixed content. Multiple elements MAY be included, as long
as each such element possesses an 'xml:lang' attribute with a
distinct value.
Example: A message with a subject:
I implore you!
Úpěnlivě prosim!
Wherefore art thou, Romeo?
PročeŽ jsi ty, Romeo?
3.5 Specifying a Conversation Thread
A message stanza MAY contain a child element specifying the
conversation thread in which the message is situated, for the purpose
of tracking the conversation. The content of the element is
a random string that is generated by the sender in accordance with
the algorithm specified in XMPP Core [1]; this string SHOULD be
copied back to the sender in subsequent replies.
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Example: A threaded conversation:
Art thou not Romeo, and a Montague?
e0ffe42b28561960c6b12b944a092794b9683a38
Neither, fair saint, if either thee dislike.
e0ffe42b28561960c6b12b944a092794b9683a38
How cam'st thou hither, tell me, and wherefore?
e0ffe42b28561960c6b12b944a092794b9683a38
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4. Exchanging Presence Information
Exchanging presence information is made relatively straightforward
within XMPP by using presence stanzas. However, we see here a
contrast to the handling of messages: although a client MAY send
directed presence information to another entity, normally presence
information is sent from a client to its server (with no 'to'
address) and then broadcasted by the server to any entities that are
subscribed to the presence of the sending entity. (Note: in the
terminology of RFC 2778 [5], the only watchers in XMPP are
subscribers.)
For information regarding the syntax of presence stanzas as well as
their defined attributes and child elements, refer to XMPP Core [1].
4.1 Client and Server Responsibilities
When a client connects to its server, it SHOULD (but is NOT REQUIRED
to) send initial presence to the server in order to signal its
availability for communications. As defined herein, the initial
presence stanza (1) MUST possess no 'to' address (signalling that it
is meant to be handled by the server on behalf of the user) and (2)
MUST possess no 'type' attribute (signalling the user's
availability).
Upon receiving initial presence from a client, the user's server MUST
do the following:
1. Send presence probes (i.e., presence stanzas whose 'type'
attribute is set to a value of "probe") from the full JID
() of the user to the bare JID
() of any contacts to which the user is subscribed
in order to determine if they are available; such contacts are
those which are present in the user's roster with the
'subscription' attribute set to a value of "to" or "both". (Note:
a user or client SHOULD NOT send presence probes.)
2. Broadcast initial presence from the full JID () of the user to the bare JID () of any
contacts that are subscribed to the user's presence; such
contacts are those which are present in the user's roster with
the 'subscription' attribute set to a value of "from" or "both".
Upon receiving a presence probe from the user, the contact's server
MUST send to the user the last known availability information (i.e.,
the full XML of the last presence stanza) provided by each of the
contact's active sessions (if there exist no active sessions, the
server SHOULD NOT reply to the presence probe). The server MUST send
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this information subject to domain-specific access rules, and only if
the user is in the contact's roster with a subscription state of
"from" or "both" and the contact has not blocked outbound presence
notifications to the user's bare or full JID (as defined in Section
8.11). (Note: if the server receives a presence probe from a
subdomain of the server's hostname or another such trusted service,
it MAY provide presence information about the user to that entity.)
Upon receiving initial presence from the user, the contact's server
MUST deliver the user's presence stanza to the full JIDs
() associated with all of the contact's
active sessions, but only if the user is in the contact's roster with
a subscription state of "to" or "both" and the contact has not
blocked inbound presence notifications from the user's bare or full
JID (as defined in Section 8.10).
If the user's server receives a presence stanza of type "error" in
response to the initial presence that it forwarded to a contact on
behalf of the user, it MUST NOT send further presence updates to that
contact (until and unless it receives a presence probe from the
contact).
After sending initial presence, the user MAY update and broadcast its
presence information at any time during its active session by sending
a presence stanza with no 'to' address and either no 'type' attribute
or a 'type' attribute with a value of "unavailable". (Note: a user's
client SHOULD NOT send a presence update to broadcast information
that changes independently of the user's presence and availability.)
If the presence stanza lacks a 'type' attribute (i.e., expresses
availability), the user's server MUST broadcast the full XML of that
presence stanza to all contacts (1) that are in the user's roster
with a subscription type of "from" or "both", (2) to whom the user
has not blocked outbound presence, and (3) from whom the server has
not received a presence error during the user's session. If the
presence stanza has a 'type' attribute set to a value of
"unavailable", the user's server MUST broadcast the full XML of that
presence stanza to all contacts meeting the three conditions just
mentioned, as well as to any entities to which the user has sent
directed available presence during the user's session (if the user
has not yet sent directed unavailable presence to that entity).
A user MAY send directed presence to another entity (i.e., a presence
stanza with a 'to' attribute whose value is the JID of the other
entity and with either no 'type' attribute or a 'type' attribute
whose value is "unavailable"). There are three possible cases:
1. If the user sends directed presence to a contact that is in the
user's roster with a subscription type of "from" or "both" after
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having sent initial presence and before sending unavailable
presence broadcast, the user's server MUST route or deliver the
full XML of that presence stanza (subject to privacy rules) but
SHOULD NOT otherwise modify the contact's status regarding
presence broadcast (i.e., it SHOULD include the contact's JID in
any subsequent presence broadcasts initiated by the user).
2. If the user sends directed presence to an entity that is not in
the user's roster with a subscription type of "from" or "both"
after having sent initial presence and before sending unavailable
presence broadcast, the user's server MUST route or deliver the
full XML of that presence stanza to the entity but MUST NOT
modify the contact's status regarding available presence
broadcast (i.e., it MUST NOT include the entity's JID in any
subsequent broadcasts of available presence initiated by the
user); however, if the connected resource from which the user
sent the directed presence become unavailable, the user's server
MUST broadcast that unavailable presence to the entity (if the
user has not yet sent directed unavailable presence to that
entity).
3. If the user sends directed presence without ever first sending
initial presence or after having sent unavailable presence
broadcast, the user's server MUST treat the entities to which the
user sends directed presence in the same way that it treats the
entities listed in Case 2 above.
Before ending its session with a server, a client SHOULD gracefully
become unavailable by sending a final presence stanza that possesses
no 'to' attribute and that possesses a 'type' attribute whose value
is "unavailable" (optionally, the final presence stanza MAY contain
one or more elements specifying the reason why the user is
no longer available). However, the user's server MUST NOT depend on
receiving final presence from an available resource, since the
resource may become unavailable unexpectedly. If the user's server
detects that one of the user's resources has become unavailable for
any reason (either gracefully or ungracefully), it MUST broadcast
unavailable presence to all contacts (1) that are in the user's
roster with a subscription type of "from" or "both", (2) to whom the
user has not blocked outbound presence, and (3) from whom the server
has not received a presence error during the user's session; the
user's server MUST also send that unavailable presence stanza to any
entities to which the user has sent directed presence during the
user's session for that resource (if the user has not yet sent
directed unavailable presence to that entity).
4.2 Specifying Availability Status
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A client MAY provide further information about its availability
status by using the element. As mentioned in XMPP Core [1],
the recognized values for the show element are:
o away -- The entity or resource is temporarily away.
o chat -- The entity or resource is actively interested in chatting.
o xa -- The entity or resource is away for an extended period (xa =
"eXtended Away").
o dnd -- The entity or resource is busy (dnd = "Do Not Disturb").
Example: Availability status:
dnd
If no element is provided, the entity is assumed to be online
and available.
4.3 Specifying Detailed Status Information
In conjunction with the element, a client MAY provide
detailed status information by using the element. The
content of this element is a natural-language description of the
user's current availability status. The content of the status element
MUST be XML character data and the element MUST NOT contain mixed
content. Multiple elements MAY be included, as long as each
such element possesses an 'xml:lang' attribute with a distinct value.
Example: Detailed status information:
dnd
Wooing Juliet
Ja dvořím Juliet
4.4 Specifying Presence Priority
A client MAY provide a priority for its resource by using the
element. The content of this element is an integer whose
value is between -128 and +127. If a client does not provide the
priority element in a presence stanza, its server SHOULD assume that
the priority value is zero.
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Example: Presence priority:
dnd
Wooing Juliet
Ja dvořím Juliet
1
4.5 Determining When a Contact Went Offline
The server MUST maintain a record of the time at which a user became
unavailable (whether gracefully or ungracefully). An authorized
subscriber to that user's presence MAY request the time of last
activity by sending an IQ stanza to the user's bare JID
() containing an empty element qualified by the
'jabber:iq:last' namespace:
Example: Requesting the last active time of an offline user:
If the entity requesting the time of last activity is an authorized
subscriber to the user's presence (i.e., exists in the user's roster
with the 'subscription' attribute set to a value of "from" or "both")
and the user is not blocking IQ stanzas to and from the entity (as
defined in Section 8.12), the server SHOULD return an IQ stanza of
type "result" with the number of seconds since the user was last
active:
Example: Returning the last active time of an offline user:
If the entity requesting the time of last activity is not an
authorized subscriber to the user's presence (i.e., does not exist in
the user's roster with the 'subscription' attribute set to a value of
"from" or "both"), the server MUST return an IQ stanza of type
"error" with an error condition of forbidden:
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Example: Requester is forbidden to view the last active time of an
offline user:
Note: this document defines responses to requests for last active
time only with regard to JIDs of the form , and only
with regard to JIDs that correspond to an (offline) instant messaging
user. The behavior of other JID forms (e.g.,
or ) and entity types (e.g., online user or host) is out of
scope and undefined.
4.6 Presence Examples
The examples in this section illustrate the presence-related
protocols described above. The user is romeo@montague.net, he has
authorized a resource "orchard", and he has the following individuals
in his roster:
o juliet@capulet (subscription="both" and she has two active
sessions, one whose resource is "chamber" and another whose
resource is "balcony")
o benvolio@shakespeare.lit (subscription="to")
o mercutio@verona.it (subscription="from")
Example 1: User sends initial presence:
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Example 2: User's server sends presence probe to contacts with
subscription="to" and subscription="both" on behalf of the user's
connected resource:
Example 3: User's server sends initial presence to contacts with
subscription="from" and subscription="both" on behalf of the user's
connected resource:
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Example 4: Contacts' server replies to presence probe on behalf of
all of the contact's available resources:
away
be right back
0
1
dnd
gallivanting
Example 5: Contact's server delivers user's initial presence to all
of the contact's available resources or returns error to user:
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Example 6: User sends directed presence to another user not in his
roster:
dnd
courting Juliet
0
Example 7: User sends updated available presence information for
broadcasting:
away
I shall return!
1
Example 8: Updated presence information is delivered only to one
contact (not those from whom an error was received or to whom the
user sent directed presence):
away
I shall return!
1
away
I shall return!
1
Example 9: One of the contact's resources sends final presence:
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Example 10: Contact's server sends unavailable presence information
to user:
Example 11: User sends final presence:
gone home
Example 12: Unavailable presence information is delivered to
contact's one remaining resource as well as to the person to whom the
user sent directed presence:
gone home
gone home
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5. Managing Subscriptions
In order to protect the privacy of instant messaging users and any
other entities, presence and availability information is disclosed
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. A
subscription lasts across sessions; indeed, it lasts until the
subscriber unsubscribes or the subscribee cancels the
previously-granted subscription. Subscriptions are managed within
XMPP by sending presence stanzas containing specially-defined
attributes.
Note: there are important interactions between subscriptions and
rosters; these are defined under Integration of Roster Items and
Presence Subscriptions (Section 7), and the reader must refer to that
section for a complete understanding of presence subscriptions.
5.1 Requesting a Subscription
A request to subscribe to another entity's presence is made by
sending a presence stanza of type "subscribe".
Example: Sending a subscription request:
If the subscription request is being sent to another instant
messaging user, the JID supplied in the 'to' attribute SHOULD be of
the form rather than .
A user's server MUST NOT automatically accept subscription requests
on the user's behalf. All subscription requests MUST be directed to
the user's client. If there is no available resource associated with
the user when the subscription request is received by the server, the
user's server MUST store the subscription request offline for
delivery when the user next becomes available. (Note: if a resource
has authorized a session but has not provided initial presence, the
server SHOULD NOT consider it to be available and therefore SHOULD
NOT send subscription requests to it.)
5.2 Handling a Subscription Request
When a client receives a subscription request from another entity, it
MUST either accept the request by sending a presence stanza of type
"subscribed" or decline the request by sending a presence stanza of
type "unsubscribed".
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Example: Accepting a subscription request:
Example: Denying a presence subscription request:
5.3 Cancelling a Subscription from Another Entity
If a user would like to cancel a previously-granted subscription
request, it sends a presence stanza of type "unsubscribed".
Example: Cancelling a previously granted subscription request:
5.4 Unsubscribing from Another Entity's Presence
If a user would like to unsubscribe from the presence of another
entity, it sends a presence stanza of type "unsubscribe".
Example: Unsubscribing from an entity's presence:
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6. Managing One's Roster
In XMPP, one's contact list is called a roster, which consists of any
number of specific roster items, each roster item being identified by
a unique JID (usually of the form ). A user's roster
is stored by the user's server on the user's behalf so that the user
may access roster information from any available resource.
Note: there are important interactions between rosters and
subscriptions; these are defined under Integration of Roster Items
and Presence Subscriptions (Section 7), and the reader must refer to
that section for a complete understanding of roster management.
6.1 Retrieving One's Roster on Login
Upon connecting to the server, a client SHOULD request the roster
(however, because receiving the roster may not be desirable for all
resources, e.g., a connection with limited bandwidth, the client's
request for the roster is NOT REQUIRED). If an available resource
does not request the roster during a session, the server SHOULD NOT
send it presence subscriptions and associated "roster pushes".
Example: Client requests current roster from server:
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Example: Client receives roster from the server:
-
Friends
-
Friends
-
Friends
6.2 Adding a Roster Item
At any time, a user MAY add an item to his or her roster.
Example: Client adds a new item:
-
Servants
The value of the 'jid' attribute SHOULD be of the form ,
especially if the item is associated with another (human) instant
messaging user.
The server MUST update the roster information in persistent storage,
and also push the change out to all of the user's available resources
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that have requested the roster. This "roster push" consists of an IQ
set from the server to the client and enables all available resources
to remain in sync with the server-based roster information.
Example: Server (1) pushes the updated roster information to all
available resources and (2) replies with an IQ result to the sending
resource:
-
Servants
-
Servants
Example: Connected resources reply with an IQ result to the server:
6.3 Updating a Roster Item
Updating an existing roster item (e.g., changing the group) is done
in the same way as adding a new roster item, i.e., by sending the
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roster item in an IQ set to the server.
Example: User updates roster item (added group):
-
Friends
Lovers
As with adding a roster item, when updating a roster item the server
MUST update the roster information in persistent storage, and also
initiate a "roster push" to all of the user's available resources
that have requested the roster.
6.4 Deleting a Roster Item
At any time, a user MAY delete an item from its roster by doing an IQ
set and making sure that the value of the 'subscription' attribute is
"remove" (a compliant server MUST ignore any other values of the
'subscription' attribute when received from a client).
Example: Client removes an item:
As with adding a roster item, when deleting a roster item the server
MUST update the roster information in persistent storage, initiate a
"roster push" to all of the user's available resources that have
requested the roster (with the 'subscription' attribute set to a
value of "remove"), and send an IQ result to the initiating resource.
For further information about the implications of this command, see
Section 7.6.
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7. Integration of Roster Items and Presence Subscriptions
7.1 Overview
Some level of integration between roster items and presence
subscriptions is normally expected by an instant messaging user
regarding the user's subscriptions to and from other contacts. This
section describes the level of integration that must be supported
within XMPP IM.
There are four primary subscription states:
o None -- Neither the user nor the contact is subscribed to the
other's presence
o To -- The user is subscribed to the contact's presence but there
is no subscription from the contact to the user
o From -- There is a subscription from the contact to the user, but
the user has not subscribed to the contact's presence
o Both -- Both the user and the contact are subscribed to each
other's presence (i.e., the union of 'from' and 'to')
Each of these states is reflected in the roster of both the user and
the contact, thus resulting in durable subscription states. A
detailed explanation of how these subscription states interact with
roster items is provided in the following sub-sections.
If a connected resource does not both send initial presence and
request the roster, the server SHOULD NOT send it presence
subscription requests or "roster pushes".
The 'from' and 'to' addresess are OPTIONAL in roster pushes; if
included, their values SHOULD be the full JID of the resource for
that session. A client MUST acknowledge each "roster push" with an IQ
stanza of type "result" (for the sake of brevity, these stanzas are
not shown in the following examples but are required by XMPP Core
[1]).
7.2 User Subscribes to Contact
The process by which a user subscribes to a contact, including the
interaction between roster items and subscription states, is defined
below.
1. In preparation for being able to render the contact in the user's
client interface and for the server to keep track of the
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subscription, the user's client SHOULD perform a "roster set" for
the new roster item. This request consists of an IQ stanza of
type='set' containing a element in the
'jabber:iq:roster' namespace, which in turn contains an
element that defines the new roster item; the element
MUST possess a 'jid' attribute, MAY possess a 'name' attribute,
MUST NOT possess a 'subscription' attribute, and MAY contain one
or more child elements:
-
MyBuddies
2. As a result, the user's server (1) MUST initiate a "roster push"
for the new roster item to all available resources associated
with this user that have requested the roster, setting the
'subscription' attribute to a value of "none"; and (2) MUST reply
with an IQ stanza of type='result':
-
MyBuddies
3. If the user wants to request a subscription to the contact's
presence, the user's client MUST send a presence stanza of
type='subscribe' to the contact:
4. As a result, the user's server MUST initiate a second "roster
push" to all of the user's available resources that have
requested the roster, setting the contact to the pending
sub-state of the 'none' subscription state; this pending
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sub-state is denoted by the inclusion of the ask='subscribe'
attribute in the roster item:
-
MyBuddies
Note: if the user did not create a roster item before sending the
subscription request, the server MUST now create one and send a
"roster push" to all of the user's available resources that have
requested the roster, absent the 'name' attribute and the child.
5. The user's server MUST also stamp the presence stanza of type
"subscribe" with the user's bare JID (i.e., ) as the
'from' address. If the contact is served by a different host than
the user, the user's server MUST route the presence stanza to the
contact's server for delivery to the contact (this case is
assumed throughout; however, if the contact is served by the same
host, then the server can simply deliver the presence stanza
directly):
6. Upon receiving the presence stanza of type "subscribe" addressed
to the contact, the contact's server must determine if there is
at least one active session in which the contact has sent
available presence and has requested the roster. If so, it MUST
deliver the subscription request to the contact (if not, the
contact's server MUST store the subscription request offline for
delivery when this condition is next met). No matter when the
subscription request is delivered, the contact must decide
whether or not to accept it (subject to configured preferences,
the contact's client MAY accept or deny the subscription request
without presenting it to the contact). Here we assume the "happy
path" that the contact accepts the subscription request (the
alternate flow of declining the subscription request is defined
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in Section 7.2.1). In this case, the contact's client (1) SHOULD
perform a roster set specifying the desired nickname and group
for the user; and (2) MUST send a presence stanza of type
"subscribed" to the user in order to accept the subscription
request.
-
SomeGroup
7. As a result, the contact's server (1) MUST initiate a "roster
push" to all available resources associated with the contact that
have requested the roster, containing a roster item for the user
with the subscription state set to 'from'; (2) MUST route the
presence stanza of type "subscribed" to the user; and (3) MUST
send available presence from all of the contact's available
resources to the user:
-
SomeGroup
8. Upon receiving the presence stanza of type "subscribed" addressed
to the user, the user's server MUST first verify that the contact
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is in the user's roster with either of the following states: (a)
subscription='none', ask='subscribe' or (b) subscription='from',
ask='subscribe'. If the contact is not in the user's roster with
either of those states, the user's server MUST silently ignore
the presence stanza of type "subscribed" (i.e., it MUST NOT route
it to the user, modify the user's roster, or generate a roster
push to the user's available resources). If the contact is in the
user's roster with either of those states, the user's server (1)
MUST deliver the presence stanza of type "subscribed" from the
contact to the user; (2) MUST initiate a "roster push" to all of
the user's available resources that have requested the roster,
containing an updated roster item for the contact with the
'subscription' attribute set to a value of "to"; and (3) MUST
deliver the available presence stanza received from each of the
contact's available resources to each of the user's available
resources:
-
MyBuddies
From the perspective of the user, there now exists a subscription to
the contact; from the perspective of the contact, there now exists a
subscription from the user. (Note: If at this point the user sends
another subscription request to the contact, the user's server MUST
silently ignore that request.)
7.2.1 Alternate Flow: Contact Declines Subscription Request
The above activity flow represents the "happy path" related to the
user's subscription request to the contact. The main alternate flow
occurs if the contact denies the user's subscription request.
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1. If the contact wants to deny the request, the contact's client
MUST send a presence stanza of type "unsubscribed" to the user
(instead of the presence stanza of type "subscribed" sent in Step
6 of Section 7.2):
2. As a result, the contact's server MUST route the presence stanza
of type "unsubscribed" to the user, first stamping the 'from'
address as the bare JID () of the contact:
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the user, the user's server (1) MUST deliver that
presence stanza to the user and (2) MUST initiate a "roster push"
to all of the user's available resources that have requested the
roster, containing an updated roster item for the contact with
the 'subscription' attribute set to a value of "none" and with no
'ask' attribute:
-
MyBuddies
As a result of this activity, the contact is now in the user's roster
with a subscription state of "none", whereas the user is not in the
contact's roster at all.
7.3 Creating a Mutual Subscription
The user and contact can build on the foregoing to create a mutual
subscription (i.e., a subscription of type "both"). The process is
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defined below.
1. If the contact wants to create a mutual subscription, the contact
MUST send a subscription request to the user (subject to
configured preferences, the contact's client MAY send this
automatically):
2. As a result, the contact's server (1) MUST initiate a "roster
push" to all available resources associated with the contact that
have requested the roster, with the user still in the 'from'
subscription state but with a pending 'to' subscription denoted
by the inclusion of the ask='subscribe' attribute in the roster
item; and (2) MUST route the presence stanza of type "subscribe"
to the user, first stamping the 'from' address as the bare JID
() of the contact:
-
SomeGroup
3. Upon receiving the presence stanza of type "subscribe" addressed
to the user, the user's server must determine if there is at
least one active session in which the user has sent available
presence and has requested the roster. If so, the user's server
MUST deliver the subscription request to the user (if not, it
MUST store the subscription request offline for delivery when
this condition is next met). No matter when the subscription
request is delivered, the user must then decide whether or not to
accept it (subject to configured preferences, the user's client
MAY accept or deny the subscription request without presenting it
to the user). Here we assume the "happy path" that the user
accepts the subscription request (the alternate flow of declining
the subscription request is defined in Section 7.3.1). In this
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case, the user's client MUST send a presence stanza of type
"subscribed" to the contact in order to accept the subscription
request.
4. As a result, the user's server (1) MUST initiate a "roster push"
to all of the user's available resources that have requested the
roster, containing a roster item for the contact with the
'subscription' attribute set to a value of "both"; (2) route the
presence stanza of type "subscribed" to the contact, first
stamping the 'from' address as the bare JID () of
the user; and (3) send available presence from each of the user's
available resources to the contact:
-
MyBuddies
5. Upon receiving the presence stanza of type "subscribed" addressed
to the contact, the contact's server MUST first verify that the
user is in the contact's roster with either of the following
states: (a) subscription='none', ask='subscribe' or (b)
subscription='from', ask='subscribe'. If the user is not in the
contact's roster with either of those states, the contact's
server MUST silently ignore the presence stanza of type
"subscribed" (i.e., it MUST NOT route it to the contact, modify
the contact's roster, or generate a roster push to the contact's
available resources). If the user is in the contact's roster with
either of those states, the contact's server (1) MUST deliver the
presence stanza of type "subscribed" from the user to the
contact; (2) MUST initiate a "roster push" to all available
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resources associated with the contact that have requested the
roster, containing an updated roster item for the user with the
'subscription' attribute set to a value of "both"; and (3) MUST
deliver the available presence stanza received from each of the
user's available resources to each of the contact's available
resources:
-
SomeGroup
The user and the contact now have a mutual subscription to each
other's presence -- i.e., the subscription is of type "both". The
user's server MUST now send the user's current presence information
to the contact. (Note: If at this point the user sends a subscription
request to the contact or the contact sends a subscription request to
the user, the sending user's server MUST silently ignore that request
and not route it to the intended recipient.)
7.3.1 Alternate Flow: User Declines Subscription Request
The above activity flow represents the "happy path" related to the
contact's subscription request to the user. The main alternate flow
occurs if the user denies the contact's subscription request.
1. If the user wants to deny the request, the user's client MUST
send a presence stanza of type "unsubscribed" to the contact
(instead of the presence stanza of type "subscribed" sent in Step
3 of Section 7.3):
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2. As a result, the user's server MUST route the presence stanza of
type "unsubscribed" to the contact, first stamping the 'from'
address as the bare JID () of the user:
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the contact, the contact's server (1) MUST deliver
that presence stanza to the contact; and (2) MUST initiate a
"roster push" to all available resources associated with the
contact that have requested the roster, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "from" and with no 'ask' attribute:
-
SomeGroup
As a result of this activity, there has been no change in the
subscription state; i.e., the contact is in the user's roster with a
subscription state of "to" and the user is in the contact's roster
with a subscription state of "from".
7.4 Unsubscribing
At any time after subscribing to a contact's presence, a user MAY
unsubscribe. While the XML that the user sends to make this happen is
the same in all instances, the subsequent subscription state is
different depending on the subscription state obtaining when the
unsubscribe "command" was sent. Both possible scenarios are defined
below.
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7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual
In the first case, the user has a subscription to the contact but the
contact does not have a subscription to the user (i.e., the
subscription is not yet mutual).
1. If the user wants to unsubscribe from the contact's presence, the
user MUST send a presence stanza of type "unsubscribe" to the
contact:
2. As a result, the user's server (1) MUST send a "roster push" to
all of the user's available resources that have requested the
roster, containing an updated roster item for the contact with
the 'subscription' attribute set to a value of "none"; and (2)
MUST route the presence stanza of type "unsubscribe" to the
contact, first stamping the 'from' address as the bare JID
() of the user:
-
MyBuddies
3. Upon receiving the presence stanza of type "unsubscribe"
addressed to the contact, the contact's server (1) MUST initiate
a "roster push" to all available resources associated with the
contact that have requested the roster, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "none" (if the contact is offline, the contact's
server MUST modify the roster item and send that modified item
the next time the contact requests the roster); and (2) SHOULD
deliver the unsubscribe command to the contact:
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-
SomeGroup
4. The contact's server then (1) MAY send a presence stanza of type
"unsubscribed" to the user; and (2) SHOULD send unavailable
presence from the contact to the user:
5. If the user's server receives a presence stanza of type
"unsubscribed" and/or unavailable presence, it MUST deliver them
to the user:
7.4.2 Case #2: Unsubscribing When Subscription is Mutual
In the second case, the user has a subscription to the contact and
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the contact also has a subscription to the user (i.e., the
subscription is mutual).
1. If the user wants to unsubscribe from the contact's presence, the
user MUST send a presence stanza of type "unsubscribe" to the
contact:
2. As a result, the user's server (1) MUST send a "roster push" to
all of the user's available resources that have requested the
roster, containing an updated roster item for the contact with
the 'subscription' attribute set to a value of "from"; and (2)
route the presence stanza of type "unsubscribe" to the contact,
first stamping the 'from' address as the bare JID ()
of the user:
-
MyBuddies
3. Upon receiving the presence stanza of type "unsubscribe"
addressed to the contact, the contact's server (1) MUST initiate
a "roster push" to all available resources associated with the
contact that have requested the roster, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "to" (if the contact is offline, the contact's server
MUST modify the roster item and send that modified item the next
time the contact requests the roster); and (2) SHOULD deliver the
unsubscribe command to the contact:
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-
SomeGroup
4. The contact's server then (1) MAY send a presence stanza of type
"unsubscribed" to the user; and (2) SHOULD send unavailable
presence from the contact to the user:
5. If the user's server receives a presence stanza of type
"unsubscribed" and/or unavailable presence, it MUST deliver them
to the user:
Note: Obviously this does not result in removal of the roster item
from the user's roster, and the contact still has a subscription to
the user's presence. In order to both completely cancel a mutual
subscription and fully remove the roster item from the user's roster,
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the user should update the roster item with subscription='remove' as
defined in Section 7.6.
7.5 Cancelling a Subscription
At any time after approving a subscription request from a user, a
contact MAY cancel that subscription. While the XML that the contact
sends to make this happen is the same in all instances, the
subsequent subscription state is different depending on the
subscription state obtaining when the cancellation was sent. Both
possible scenarios are defined below.
7.5.1 Case #1: Cancelling When Subscription is Not Mutual
In the first case, the user has a subscription to the contact but the
contact does not have a subscription to the user (i.e., the
subscription is not yet mutual).
1. If the contact wants to cancel the user's subscription, the
contact MUST send a presence stanza of type "unsubscribed" to the
user:
2. As a result, the contact's server (1) MUST send a "roster push"
to all of the contact's available resources that have requested
the roster, containing an updated roster item for the user with
the 'subscription' attribute set to a value of "none"; (2) MUST
route the presence stanza of type "unsubscribed" to the user,
first stamping the 'from' address as the bare JID
() of the contact; and (3) SHOULD send
unavailable presence from the contact to the user:
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-
SomeGroup
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the user, the user's server (1) MUST initiate a
"roster push" to all of the user's available resources that have
requested the roster, containing an updated roster item for the
contact with the 'subscription' attribute set to a value of
"none" (if the user is offline, the user's server MUST modify the
roster item and send that modified item the next time the user
requests the roster); and (2) SHOULD deliver the presence stanza
of type "unsubscribed" to the user:
-
MyBuddies
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4. Upon receiving the presence stanza of type "unavailable"
addressed to the user, the user's server MUST deliver the
unavailable presence to the user:
7.5.2 Case #2: Cancelling When Subscription is Mutual
In the second case, the user has a subscription to the contact and
the contact also has a subscription to the user (i.e., the
subscription is mutual).
1. If the contact wants to cancel the user's subscription, the
contact MUST send a presence stanza of type "unsubscribed" to the
user:
2. As a result, the contact's server (1) MUST send a "roster push"
to all of the contact's available resources that have requested
the roster, containing an updated roster item for the user with
the 'subscription' attribute set to a value of "to"; (2) MUST
route the presence stanza of type "unsubscribed" to the user,
first stamping the 'from' address as the bare JID
() of the contact; and (3) SHOULD send
unavailable presence from the contact to the user:
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SomeGroup
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the user, the user's server (1) MUST initiate a
"roster push" to all of the user's available resources that have
requested the roster, containing an updated roster item for the
contact with the 'subscription' attribute set to a value of
"from" (if the user is offline, the user's server MUST modify the
roster item and send that modified item the next time the user
requests the roster); and (2) SHOULD deliver the presence stanza
of type "unsubscribed" to the user:
-
MyBuddies
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4. Upon receiving the presence stanza of type "unavailable"
addressed to the user, the user's server MUST deliver the
unavailable presence to the user:
Note: Obviously this does not result in removal of the roster item
from the contact's roster, and the contact still has a subscription
to the user's presence. In order to both completely cancel a mutual
subscription and fully remove the roster item from the contact's
roster, the contact should update the roster item with
subscription='remove' as defined in Section 7.6.
7.6 Removing a Roster Item and Cancelling All Subscriptions
Because there may be many steps involved in completely removing a
roster item and cancelling subscriptions in both directions, XMPP IM
includes a "shortcut" method for doing so. The process may be
initiated no matter what the current subscription state is by sending
a roster set containing an item for the contact with the
'subscription' attribute set to a value of "remove":
When the user removes a contact from his or her roster by setting the
'subscription' attribute to a value of "remove", the user's server
(1) MUST automatically cancel any existing presence subscription
between the user and the contact (both 'to' and 'from' as
appropriate); (2) MUST remove the roster item from the user's roster
and inform all of the user's available resources of the roster item
removal; (3) MUST inform the resource that initiated the removal of
success; and (4) SHOULD send unavailable presence to the contact:
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Upon receiving the presence stanza of type "unsubscribe", the
contact's server (1) MUST initiate a "roster push" to all available
resources associated with the contact that have requested the roster,
containing an updated roster item for the user with the
'subscription' attribute set to a value of "to" (if the contact is
offline, the contact's server MUST modify the roster item and send
that modified item the next time the contact requests the roster);
and (2) SHOULD also deliver the unsubscribe command to the contact:
-
SomeGroup
Upon receiving the presence stanza of type "unsubscribed", the
contact's server (1) MUST initiate a "roster push" to all available
resources associated with the contact that have requested the roster,
containing an updated roster item for the user with the
'subscription' attribute set to a value of "none" (if the contact is
offline, the contact's server MUST modify the roster item and send
that modified item the next time the contact requests the roster);
and (2) SHOULD also deliver the unsubscribe command to the contact:
-
SomeGroup
Upon receiving the presence stanza of type "unavailable" addressed to
the contact, the contact's server MUST deliver the unavailable
presence to the user:
Note that when the user removes the contact from the user's roster,
the end state of the contact's roster is that the user is still in
the contact's roster with a subscription state of "none"; in order to
completely remove the roster item for the user, the contact needs to
also send a roster removal request.
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8. Blocking Communication
Most instant messaging systems have found it necessary to implement
some method for users to block communications from particular other
users (this is also required by sections 5.1.5, 5.1.15, 5.3.2, and
5.4.10 of RFC 2779 [2]). In XMPP this is done using the
'jabber:iq:privacy' namespace by managing one's privacy lists.
Server-side privacy lists enable successful completion of the
following use cases:
o Retrieving one's privacy lists.
o Adding, removing, and editing one's privacy lists.
o Setting, changing, or declining active lists.
o Setting, changing, or declining the default list (i.e., the list
that is active by default).
o Allowing or denying messages based on JID, group, or subscription
type (or globally).
o Allowing or denying inbound presence notifications based on JID,
group, or subscription type (or globally).
o Allowing or denying outbound presence notifications based on JID,
group, or subscription type (or globally).
o Allowing or denying IQs based on JID, group, or subscription type
(or globally).
o Allowing or denying all communications based on JID, group, or
subscription type (or globally).
Note: presence notifications do not include presence subscriptions,
only presence information that is broadcasted to entities that are
subscribed to a user's presence information. Thus this includes
presence stanzas with no 'type' attribute or of type='unavailable'
only.
8.1 Syntax
A user MAY define one or more privacy lists, which are stored by the
user's server. Each
element contains one or more rules in the
form of elements, and each element uses attributes to
define a privacy rule type, a specific value to which the rules
applies, the relevant action, and the place of the item in the
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processing order.
The syntax is as follows:
If the type is "jid", then the 'value' attribute MUST contain a valid
Jabber ID. JIDs are matched in the following order: , then , then , then .
If the value is , then any connected resource for that
user@domain matches. If the value is , then only
that resource matches. If the value is , then any user@domain
(or subdomain) matches.
If the type is "group", then the 'value' attribute MUST contain the
name of a group in the user's roster. (If a client attempts to
update, create, or delete a list item with a group that is not in the
user's roster, the server MUST return to the client an
stanza error.)
If the type is "subscription", then the 'value' attribute MUST be one
of "both", "to", "from", or "none" as defined in XMPP Core [1].
If no 'type' attribute is included, the rule provides the
"fall-through" case.
The 'action' attribute MUST be included and its value MUST be either
"accept" or "deny".
The 'order' attribute MUST be included and its value MUST be a
non-negative integer that is unique among all items in the list. (If
a client attempts to create or update a list with non-unique order
values, the server MUST return to the client a stanza
error.
Within the 'jabber:iq:privacy' namespace, the child of a
client-generated IQ stanza of type "set" MUST NOT include more than
one child element (i.e., the stanza must contain only one
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element, one element, or one
element); if a client
violates this rule, the server MUST return to the client a
stanza error.)
When a client adds or updates a privacy list, the
element
MUST contain at least one child element; if a client violates
this rule, the server MUST return to the client a
stanza error.
When a client updates a privacy list, it must include all of the
desired items (i.e., not a "delta").
8.2 Business Rules
1. If there is an active list set for a session, it affects only the
session for which it is activated, and only for the duration of
the session. Only the active list for that session is processed
(i.e., the default list is ignored).
2. The default list applies to the user as a whole, and is processed
if there is no active list set for the target session/resource to
which a stanza is addressed, or if there are no current sessions
for the user.
3. If there is no active list set for a session (or there are no
current sessions for the user), and there is no default list,
then all stanzas SHOULD BE accepted or appropriately processed by
the server on behalf of the user.
4. Privacy lists SHOULD be the first routing and delivery rule
applied by a server, trumping the other rules specified in
Section 9.
5. The order in which privacy list items are processed by the server
is important. List items MUST be processed in ascending order
determined by the values of the 'order' attribute for each - .
6. As soon as a stanza is matched against a privacy list, the server
SHOULD appropriately handle the stanza and cease processing.
7. If no fall-through item is provided in a list, the fall-through
action is assumed to be "accept".
8. When a user updates the definition for a list or adds a new list
(whether or not it is active), the server SHOULD NOT "push" that
information out to all of the user's available resources that
have requested the roster's account, as is done for rosters. If a
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client or user wants to retrieve the current privacy list
information, it SHOULD request the relevant list.
9. If a change to the subscription state or roster group of a roster
item occurs during a user's session and the active session,
subsequent processing of the active list MUST be based on the
changed state or group.
8.3 Retrieving One's Privacy Lists
Example: Client requests names of privacy lists from server:
Example: Server sends names of privacy lists to client, preceded by
active list and default list:
Example: Client requests a privacy list from server:
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Example: Server sends a privacy list to client:
Example: Client requests another privacy list from server:
Example: Server sends another privacy list to client:
Example: Client requests yet another privacy list from server:
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Example: Server sends yet another privacy list to client:
In this example, the user has three lists: (1) 'public', which allows
communications from everyone except one specific entity (this is the
default list); (2) 'private', which allows communications only with
contacts who have a bidirectional subscription with the user (this is
the active list); and (3) 'special', which allows communications only
with three specific entities.
If the user attempts to retrieve a list but a list by that name does
not exist, the server MUST return an stanza error to
the user:
Example: Client attempts to retrieve non-existent list:
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The user is allowed to retrieve only one list at a time. If the user
attempts to retrieve more than one list in the same request, the
server MUST return a stanza error to the user:
Example: Client attempts to retrieve more than one list:
8.4 Managing Active Lists
In order to set or change the active list currently being applied by
the server, the user MUST send an IQ stanza of type "set" with a
element qualified by the 'jabber:iq:privacy' namespace that
contains an empty child element possessing a 'name'
attribute whose value is set to the desired list name.
Example: Client requests change of active list:
The server MUST activate and apply the requested list before sending
the result back to the client.
Example: Server acknowledges success of active list change:
If the user attempts to set an active list but a list by that name
does not exist, the server MUST return an stanza
error to the user:
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Example: Client attempts to set a non-existent list as active:
In order to decline the use of any active list, a user MUST send an
empty element with no name.
Example: Client declines the use of active lists:
8.5 Managing the Default List
In order to change its default list, the user MUST send an IQ stanza
of type "set" with a element qualified by the
'jabber:iq:privacy' namespace that contains an empty child
element possessing a 'name' attribute whose value is set to the
desired list name.
Example: Client requests change of default list:
Example: Server acknowledges success of default list change:
If the user attempts to set a default list but a list by that name
does not exist, the server MUST return an stanza
error to the user:
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Example: Client attempts to set a non-existent list as default:
In order to decline the use of a default list (i.e., to use the
domain's stanza routing rules at all times), a user MUST send an
empty element with no name.
Example: Client declines the use of the default list:
8.6 Editing a Privacy List
In order to edit a privacy list, the user MUST send an IQ stanza of
type "set" with a element qualified by the
'jabber:iq:privacy' namespace that contains one
child element
possessing a 'name' attribute whose value is set to the list name the
user would like to edit. The
element MUST contain one or more
elements, which specify the user's desired changes to the
list by including all elements in the list (not the "delta").
Example: Client edits a privacy list:
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Note: The value of the 'order' attribute for any given item is not
fixed. Thus in the foregoing example if the user would like to add 4
items between the "tybalt@capulet.com" item and the
"paris@shakespeare.lit" item, the user's client MUST renumber the
relevant items before submitting the list to the server.
Example: Server acknowledges success of list edit:
8.7 Adding a New Privacy List
The same protocol used to edit an existing list is used to create a
new list. If the list name matches that of an existing list, the
request to add a new list will overwrite the old one.
8.8 Removing a Privacy List
In order to remove a privacy list, the user MUST send an IQ stanza of
type "set" with a element qualified by the
'jabber:iq:privacy' namespace that contains one empty
child
element possessing a 'name' attribute whose value is set to the list
name the user would like to remove.
Example: Client removes a privacy list:
Example: Server acknowledges success of list removal:
If a user attempts to remove an active list or the default list, the
server MUST return a stanza error to the user. The user
MUST first set another list to active or default before removing it.
If the user attempts to remove a list but a list by that name does
not exist, the server MUST return an stanza error to
the user:
If the user attempts to remove more than one list in the same
request, the server MUST return a stanza error to the
user.
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8.9 Blocking Messages
Server-side privacy lists enable a user to block incoming messages
from other users based on the other user's JID, roster group, or
subscription status (or globally). The following examples illustrate
the protocol.
Example: User blocks based on JID:
-
As a result of creating and applying the foregoing list, the user
will not receive messages from the user with the specified JID.
Example: User blocks based on roster group:
-
As a result of creating and applying the foregoing list, the user
will not receive messages from any users in the specified roster
group.
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Example: User blocks based on subscription type:
-
As a result of creating and applying the foregoing list, the user
will not receive messages from any users with the specified
subscription type.
Example: User blocks globally:
-
As a result of creating and applying the foregoing list, the user
will not receive messages from any other users.
8.10 Blocking Inbound Presence Notifications
Server-side privacy lists enable a user to block incoming presence
notifications from other users based on the other user's JID, roster
group, or subscription status (or globally). The following examples
illustrate the protocol.
Note: presence notifications do not include presence subscriptions,
only presence information that is broadcasted to the user because the
user previously subscribed to a contact's presence information. Thus
this includes presence stanzas with no 'type' attribute or of
type='unavailable' only.
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Example: User blocks based on JID:
-
As a result of creating and applying the foregoing list, the user
will not receive presence notifications from the user with the
specified JID.
Example: User blocks based on roster group:
-
As a result of creating and applying the foregoing list, the user
will not receive presence notifications from any users in the
specified roster group.
Example: User blocks based on subscription type:
-
As a result of creating and applying the foregoing list, the user
will not receive presence notifications from any users with the
specified subscription type.
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Example: User blocks globally:
-
As a result of creating and applying the foregoing list, the user
will not receive presence notifications from any other users.
8.11 Blocking Outbound Presence Notifications
Server-side privacy lists enable a user to block outgoing presence
notifications to other users based on the other user's JID, roster
group, or subscription status (or globally). The following examples
illustrate the protocol.
Note: presence notifications do not include presence subscriptions,
only presence information that is broadcasted to contacts because
those contacts previously subscribed to the user's presence
information. Thus this includes presence stanzas with no 'type'
attribute or of type='unavailable' only. Note also that because
information about last activity MAY be requested by a contact (as
defined in Section 4.5), a user SHOULD block both outbound presence
and IQs in relation to any given entity.
Example: User blocks based on JID:
-
As a result of creating and applying the foregoing list, the user
will not send presence notifications to the user with the specified
JID.
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Example: User blocks based on roster group:
-
As a result of creating and applying the foregoing list, the user
will not send presence notifications to any users in the specified
roster group.
Example: User blocks based on subscription type:
-
As a result of creating and applying the foregoing list, the user
will not send presence notifications to any users with the specified
subscription type.
Example: User blocks globally:
-
As a result of creating and applying the foregoing list, the user
will not send presence notifications to any other users.
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8.12 Blocking IQs
Server-side privacy lists enable a user to block incoming IQ requests
of type "get" or "set" from other users based on the other user's
JID, roster group, or subscription status (or globally). The
following examples illustrate the protocol.
Example: User blocks based on JID:
-
As a result of creating and applying the foregoing list, the user
will not receive IQ requests of type "get" or "set" from the user
with the specified JID.
Example: User blocks based on roster group:
-
As a result of creating and applying the foregoing list, the user
will not receive IQ requests of type "get" or "set" from any users in
the specified roster group.
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Example: User blocks based on subscription type:
-
As a result of creating and applying the foregoing list, the user
will not receive IQ requests of type "get" or "set" from any users
with the specified subscription type.
Example: User blocks globally:
-
As a result of creating and applying the foregoing list, the user
will not receive IQ requests of type "get" or "set" from any other
users.
8.13 Blocking All Communication
Server-side privacy lists enable a user to block all communications
from and presence to other users based on the other user's JID,
roster group, or subscription status (or globally). The following
examples illustrate the protocol.
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Example: User blocks based on JID:
As a result of creating and applying the foregoing list, the user
will not receive any communications from, nor send any stanzas to,
the user with the specified JID.
Example: User blocks based on roster group:
As a result of creating and applying the foregoing list, the user
will not receive any communications from, nor send any stanzas to,
any users in the specified roster group.
Example: User blocks based on subscription type:
As a result of creating and applying the foregoing list, the user
will not receive any communications from, nor send any stanzas to,
any users with the specified subscription type.
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Example: User blocks globally:
As a result of creating and applying the foregoing list, the user
will not receive any communications from, nor send any stanzas to,
any other users.
8.14 Blocked Entity Attempts to Communicate with User
If a blocked entity attempts to send messages or presence
notifications to the user, the user's server SHOULD silently drop the
stanza and MUST NOT return an error to the sending entity.
If a blocked entity attempts to send an IQ stanza of type "get" or
"set" to the user, the user's server MUST return to the sending
entity a stanza error, since this is the
standard error code sent from a client that does not understand the
namespace of an IQ get or set. IQ stanzas of other types SHOULD be
silently dropped by the server.
Example: Blocked entity attempts to send IQ get:
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Example: Server returns error to blocked entity:
8.15 Higher-Level Heuristics
When building a representation of a higher-level privacy heuristic, a
client SHOULD use the simplest possible representation.
For example, the heuristic "block all communications with any user
not in my roster" could be constructed in any of the following ways:
o accept communications from all JIDs in my roster (i.e., listing
each JID as a separate list item), but deny communications with
everyone else
o accept communications from any user who is in one of the groups
that make up my roster (i.e., listing each group as a separate
list item), but deny communications from everyone else
o accept communications from any user with whom I have a
subscription of 'both' or 'to' or 'from' (i.e., listing each
subscription value separately), but deny communications from
everyone else
o deny communications from anyone whose subscription state is 'none'
The final representation is the simplest and SHOULD be used; here is
the XML that would be sent in this case:
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9. Server Rules for Handling XML Stanzas
Each server implementation will contain its own "delivery tree" for
handling stanzas it receives. Such a tree determines whether a stanza
needs to be routed to another domain, processed internally, or
delivered to a connected resource associated with a registered user.
The following rules apply:
9.1 No 'to' Address
If the stanza possesses no 'to' attribute, the server SHOULD process
it on behalf of the entity that sent it. Because all stanzas received
from other servers MUST possess a 'to' attribute, this rule applies
only to stanzas received from an entity that is connected to the
server (usually an active client session). If the server receives a
presence stanza with no 'to' attribute, the server SHOULD broadcast
it to the entities that are subscribed to the sending entity's
presence as defined under Section 4.1. If the server receives an IQ
stanza of type "get" or "set" with no 'to' attribute and it
understands the namespace that qualifies the content of the stanza,
it MUST process the stanza on behalf of sending entity (where the
meaning of "process" is determined by the semantics of the qualifying
namespace).
9.2 Foreign Domain
If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute does not match one of the configured hostnames
of the server itself or a subdomain thereof, the server SHOULD route
the stanza to the foreign domain (subject to local service
provisioning and security policies regarding inter-domain
communication). If routing to the recipient's server is unsuccessful,
the sender's server MUST return an error to the sender; if the
recipient's server can be contacted but delivery by the recipient's
server to the recipient is unsuccessful, the recipient's server MUST
return an error to the sender by way of the sender's server.
9.3 Subdomain
If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute matches a subdomain of one of the configured
hostnames of the server itself, the server MAY process the stanza
itself or MAY route the stanza to a specialized service that is
responsible for that subdomain (if any).
9.4 Bare Domain or Specific Resource
If the hostname of the domain identifier portion of the JID contained
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in the 'to' attribute matches the hostname of the server itself and
the JID contained in the 'to' attribute is of the form or
, the server (or a defined resource thereof) SHOULD
process the stanza as appropriate for the stanza type. If the stanza
is an IQ stanza and the server understands the namespace that
qualifies the content of the stanza, the server SHOULD process the
request according to the semantics of the qualifying namespace, and
MUST reply with an IQ of type "result" or "error".
9.5 User in Same Domain
If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute matches the hostname of the server itself and
the JID contained in the 'to' attribute is of the form
or , the server SHOULD first apply any privacy
rules (Section 8) that are in force. If privacy rules allow the
stanza, it SHOULD be routed or delivered to the intended recipient of
the stanza as represented by the JID contained in the 'to' attribute.
The following rules apply:
1. If the JID contains a resource identifier (i.e., is of the form
) and there is an available resource whose
authzid matches the full JID, the recipient's server SHOULD
deliver the stanza to the session that exactly matches the
resource identifier.
2. If the JID contains a resource identifier and there is no
available resource whose authzid matches the full JID, the
recipient's server SHOULD return to the sender a
stanza error.
3. If the JID is of the form and there is at least one
available resource available for the user, the recipient's server
MUST follow these rules:
1. For message stanzas, the server SHOULD deliver the stanza to
the available resource that provided the highest value for
the element (if the resource did not provide a
priority, the server SHOULD consider it to have provided a
value of zero). If two resources have the same priority, the
server MAY use some other rule (e.g., most recent connect
time or activity time) to choose between them. However, the
server MUST NOT deliver the stanza to an available resource
that provided a negative value for the element.
2. For presence stanzas other than those of type "probe", the
server MUST deliver the stanza to all available resources,
except that the server MUST NOT deliver the stanza to an
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available resource that provided a negative value for the
element; for presence probes, the server SHOULD
reply based on the rules defined in Section 4.1.
3. For IQ stanzas, the server SHOULD deliver the stanza to all
available resources, except that the server MUST NOT deliver
the stanza to an available resource that provided a negative
value for the element.
4. If the JID is of the form and there are no
available resources associated with the user (e.g., an instant
messaging user is offline), how the stanza is handled depends on
the stanza type:
1. For presence stanzas of type "subscribe", the server MUST
maintain a record of the stanza, as specified under Section
4.1.
2. For all other presence stanzas, the server SHOULD silently
ignore the stanza by not storing it for later delivery or
replying to it on behalf of the user.
3. For message stanzas, the server MAY choose to store the
stanza on behalf of the user and deliver it when the user
next becomes available. However, if offline message storage
is not enabled, the server MUST return to the sender a
stanza error. (Note: offline message
storage is not defined in XMPP since it strictly is a matter
of implementation and service provisioning.)
4. For IQ stanzas, the server MUST reply with either an IQ
result or an IQ error. Specifically, if the semantics of the
qualifying namespace define a reply that the server can
provide, the server MUST reply to the stanza on behalf of the
user (e.g., this is the case with the 'jabber:iq:last'
protocol defined above); if not, the server MUST reply with a
stanza error.
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10. IANA Considerations
For several related IANA considerations, refer to XMPP Core [1].
10.1 XML Namespace Name for Session Data
A URN sub-namespace for session-related data in the Extensible
Messaging and Presence Protocol (XMPP) is defined as follows.
URI: urn:ietf:params:xml:ns:xmpp-session
Specification: [RFCXXXX]
Description: This is the XML namespace name for session-related data
in the Extensible Messaging and Presence Protocol (XMPP) as
defined by [RFCXXXX].
Registrant Contact: IETF, XMPP Working Group,
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11. Security Considerations
For security considerations, refer to the relevant section of XMPP
Core [1].
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Normative References
[1] Saint-Andre, P. and J. Miller, "XMPP Core",
draft-ietf-xmpp-core-13 (work in progress), June 2003.
[2] Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
Presence Protocol Requirements", RFC 2779, February 2000.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
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Informative References
[4] Jabber Software Foundation, "Jabber Software Foundation", August
2001, .
[5] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
Instant Messaging", RFC 2778, February 2000, .
[6] Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC
2426, September 1998.
Authors' Addresses
Peter Saint-Andre
Jabber Software Foundation
EMail: stpeter@jabber.org
URI: http://www.jabber.org/people/stpeter.php
Jeremie Miller
Jabber Software Foundation
EMail: jeremie@jabber.org
URI: http://www.jabber.org/people/jer.php
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Appendix A. vCards
Sections 3.1.3 and 4.1.4 of RFC 2779 [2] require that it be possible
to retrieve contact information for other users (e.g., telephone
number or email address). An XML representation of the vCard
specification defined in RFC 2426 [6] is in common use within the
Jabber community to provide such information. Documentation of this
protocol is maintained by the Jabber Software Foundation [4] at
but is out of scope for this
document.
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Appendix B. XML Schemas
The following XML schemas are descriptive, not normative.
B.1 session
B.2 jabber:iq:last
B.3 jabber:iq:privacy
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B.4 jabber:iq:roster
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Appendix C. Revision History
Note to RFC Editor: please remove this entire appendix, and the
corresponding entries in the table of contents, prior to publication.
C.1 Changes from draft-ietf-xmpp-im-11
o Further clarified subscription syntax and semantics.
o Further clarified presence responsibilities for clients and
servers.
o Added 'xml:lang' example to presence status.
o Added subsection on presence priority.
o Defined server handling of unsolicited presence stanzas of type
"subscribed".
o Specified default resource priority if not provided.
o Corrected several errors in the schemas.
o Added privacy list business rule regarding roster changes.
o Removed the 'jabber:iq:privacy:error' namespace (not necessary).
o Documented message type='normal'.
o Made numerous small editorial changes throughout.
C.2 Changes from draft-ietf-xmpp-im-10
o Clarified presence responsibilities for servers and clients.
o Clarified the routing and delivery rules for servers.
o Made the 'xml:lang' examples more complete.
o Corrected several errors in the unsubscribe workflow.
o Made small editorial changes in several sections.
C.3 Changes from draft-ietf-xmpp-im-09
o Clarified rules regarding allowable JID types in rosters.
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o Further clarified the semantics and routing implications of
presence priorities.
o Removed several obsolete subsections.
C.4 Changes from draft-ietf-xmpp-im-08
o Removed authorization content (now addressed in XMPP Core).
o Added protocol for initiating an IM session, including schema and
IANA registration template.
o Corrected <*-condition/> elements to be .
o Made small editorial changes to address RFC Editor requirements.
C.5 Changes from draft-ietf-xmpp-im-07
o Added several error cases for resource authorization and updated
relevant schema.
C.6 Changes from draft-ietf-xmpp-im-06
o Specified that IQ result stanzas are required in response to
roster pushes.
o Changed stanza error namespace names to conform to the format
defined in "The IETF XML Registry" as specified in XMPP Core.
o Removed note to RFC Editor regarding provisional namespace names.
C.7 Changes from draft-ietf-xmpp-im-05
o Removed use of ask='unsubscribe' per list discussion.
o Clarified handling of resource conflict during authorization.
o Added schemas for jabber:iq:auth, jabber:iq:auth:error, and
jabber:iq:privacy:error.
o Corrected several small protocol errors in the examples.
o Clarified semantics of message types.
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C.8 Changes from draft-ietf-xmpp-im-04
o Specified sending of unavailable presence after unsubscribe and
subscription-cancellation actions.
o Further specified syntax and business rules for privacy lists.
o Brought error codes into line with definitions in
draft-ietf-xmpp-core.
o Added note to RFC Editor regarding provisional namespace names.
o Removed vCard content and DTD, instead pointing to JSF
documentation.
C.9 Changes from draft-ietf-xmpp-im-03
o Fixed order processing on privacy rules per list discussion.
o Made numerous small editorial changes.
C.10 Changes from draft-ietf-xmpp-im-02
o Added a great deal more detail to the narrative regarding
server-side privacy rules as well as the interaction between
rosters and subscriptions.
o Removed DTDs in favor of schemas (with the exception of vCard
XML).
o Removed non-normative documentation of authentication using
jabber:iq:auth and of in-band registration using
jabber:iq:register, since these are maintained by the Jabber
Software Foundation and are not part of the XMPP specification.
C.11 Changes from draft-ietf-xmpp-im-01
o Made numerous small editorial changes.
C.12 Changes from draft-ietf-xmpp-im-00
o Moved registration and authentication via jabber:iq:auth to
non-normative appendices.
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o Changed initial presence stanza from MUST be empty to SHOULD be
empty.
o Specified that user or clients should not send presence stanzas of
type='probe'.
o Specified the algorithm for digest passwords.
C.13 Changes from draft-miller-xmpp-im-02
o Added information about the 'jabber:iq:last' protocol to meet the
requirement defined in section 3.2.4 of RFC 2779.
o Added information about the 'jabber:iq:privacy' protocol to meet
the requirement defined in section 2.3.5 of RFC 2779.
o Added information about the vCard XML protocol to meet the
requirement defined in sections 3.1.3 and 4.1.4 of RFC 2779.
o Changed the material describing authentication (but not resource
authorization) with 'jabber:iq:auth' to non-normative.
o Noted that the only watchers are subscribers.
o Nomenclature changes: (1) from "chunks" to "stanzas"; (2) from
"host" to "server"; (3) from "node" to "client" or "user" (as
appropriate).
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