Network Working Group P. Saint-Andre
Internet-Draft J. Miller
Expires: November 2, 2003 Jabber Software Foundation
May 04, 2003
XMPP Instant Messaging
draft-ietf-xmpp-im-11
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 November 2, 2003.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document describes the specific extensions to and applications
of the Extensible Messaging and Presence Protocol (XMPP) that are
required to create a basic instant messaging and presence
application, such as the servers and clients that comprise the Jabber
network.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . . 9
3.5 Specifying a Conversation Thread . . . . . . . . . . . . . . 10
4. Exchanging Presence Information . . . . . . . . . . . . . . 12
4.1 Client and Server Responsibilities . . . . . . . . . . . . . 12
4.2 Specifying Availability Status . . . . . . . . . . . . . . . 15
4.3 Specifying Detailed Status Information . . . . . . . . . . . 15
4.4 Determining When a Contact Went Offline . . . . . . . . . . 16
4.5 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 . . . . . . . . . . . . . . . . . . . 27
6.4 Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 27
7. Integration of Roster Items and Presence Subscriptions . . . 29
7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.2 User Subscribes to Contact . . . . . . . . . . . . . . . . . 29
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 . . . . . 35
7.4 Unsubscribing . . . . . . . . . . . . . . . . . . . . . . . 36
7.4.1 Case #1: Subscription Type 'to' . . . . . . . . . . . . . . 36
7.4.2 Case #2: Subscription Type 'both' . . . . . . . . . . . . . 38
7.5 Cancelling a Subscription . . . . . . . . . . . . . . . . . 40
7.5.1 Case #1: Subscription Type 'from' . . . . . . . . . . . . . 40
7.5.2 Case #2: Subscription Type 'both' . . . . . . . . . . . . . 41
7.6 Removing a Roster Item and Cancelling All Subscriptions . . 42
8. Blocking Communication . . . . . . . . . . . . . . . . . . . 44
8.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.2 Business Rules . . . . . . . . . . . . . . . . . . . . . . . 46
8.3 Retrieving One's Privacy Lists . . . . . . . . . . . . . . . 47
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8.4 Managing Active Lists . . . . . . . . . . . . . . . . . . . 50
8.5 Managing the Default List . . . . . . . . . . . . . . . . . 52
8.6 Editing a Privacy List . . . . . . . . . . . . . . . . . . . 53
8.7 Adding a New Privacy List . . . . . . . . . . . . . . . . . 53
8.8 Removing a Privacy List . . . . . . . . . . . . . . . . . . 54
8.9 Blocking Messages . . . . . . . . . . . . . . . . . . . . . 54
8.10 Blocking Inbound Presence Notifications . . . . . . . . . . 56
8.11 Blocking Outbound Presence Notifications . . . . . . . . . . 58
8.12 Blocking IQs . . . . . . . . . . . . . . . . . . . . . . . . 59
8.13 Blocking All Communication . . . . . . . . . . . . . . . . . 61
8.14 Blocked Entity Attempts to Communicate with User . . . . . . 62
8.15 Higher-Level Heuristics . . . . . . . . . . . . . . . . . . 63
9. Server Rules for Handling XML Stanzas . . . . . . . . . . . 65
9.1 No 'to' Address . . . . . . . . . . . . . . . . . . . . . . 65
9.2 Foreign Domain . . . . . . . . . . . . . . . . . . . . . . . 65
9.3 Subdomain . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.4 Bare Domain or Specific Resource . . . . . . . . . . . . . . 65
9.5 User in Same Domain . . . . . . . . . . . . . . . . . . . . 66
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 68
10.1 XML Namespace Name for Session Data . . . . . . . . . . . . 68
11. Security Considerations . . . . . . . . . . . . . . . . . . 69
Normative References . . . . . . . . . . . . . . . . . . . . 70
Informative References . . . . . . . . . . . . . . . . . . . 71
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 71
A. vCards . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
B. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 73
B.1 session . . . . . . . . . . . . . . . . . . . . . . . . . . 73
B.2 jabber:iq:last . . . . . . . . . . . . . . . . . . . . . . . 73
B.3 jabber:iq:privacy . . . . . . . . . . . . . . . . . . . . . 73
B.4 jabber:iq:privacy:error . . . . . . . . . . . . . . . . . . 75
B.5 jabber:iq:roster . . . . . . . . . . . . . . . . . . . . . . 75
C. Revision History . . . . . . . . . . . . . . . . . . . . . . 77
C.1 Changes from draft-ietf-xmpp-im-10 . . . . . . . . . . . . . 77
C.2 Changes from draft-ietf-xmpp-im-09 . . . . . . . . . . . . . 77
C.3 Changes from draft-ietf-xmpp-im-08 . . . . . . . . . . . . . 77
C.4 Changes from draft-ietf-xmpp-im-07 . . . . . . . . . . . . . 77
C.5 Changes from draft-ietf-xmpp-im-06 . . . . . . . . . . . . . 78
C.6 Changes from draft-ietf-xmpp-im-05 . . . . . . . . . . . . . 78
C.7 Changes from draft-ietf-xmpp-im-04 . . . . . . . . . . . . . 78
C.8 Changes from draft-ietf-xmpp-im-03 . . . . . . . . . . . . . 78
C.9 Changes from draft-ietf-xmpp-im-02 . . . . . . . . . . . . . 79
C.10 Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . . . 79
C.11 Changes from draft-ietf-xmpp-im-00 . . . . . . . . . . . . . 79
C.12 Changes from draft-miller-xmpp-im-02 . . . . . . . . . . . . 79
Intellectual Property and Copyright Statements . . . . . . . 81
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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 scoped by particular XML namespaces. This document describes the
extensions to and applications of XMPP Core that are required to
create the basic functionality expected of an instant messaging and
presence application as defined in RFC 2779 [2].
1.2 Requirements
For the purposes of this document, we stipulate that a basic instant
messaging and presence application needs to enable a user to perform
the following high-level use cases:
o Establish a session with a server
o Exchange messages with other users
o Exchange presence information with other users
o Manage subscriptions to and from other users
o Manage the items in the user's 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 [2], and the interested reader is directed to that document
regarding the requirements addressed herein.
Note: although XMPP IM 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, mainly in 1999. In addition, protocols
addressing many other functionality areas have been defined and
continue to be defined by the Jabber Software Foundation [4]. These
include service discovery, multi-user chat, data gathering and forms
submission, feature negotiation, message composing events, message
expiration, delayed delivery, file transfer, XHTML message
formatting, publish-subscribe, and transports for XML-RPC and SOAP.
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However, such protocols are not described herein because they are not
required by RFC 2779 [2].
1.3 Terminology
This document inherits the terminology defined in XMPP Core [1].
The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [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 applications based on XMPP are implemented via
a client-server architecture that requires a user to establish a
session on the 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 -- while this is outside the scope of XMPP,
methods for doing so 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 .
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 (user@domain/
resource) associated with the connection for addressing purposes.
Once a client has authenticated with a server and authorized a full
JID (including resource), it SHOULD request that the server activate
an IM 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):
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3. Exchanging Messages
Exchanging messages is a basic use of XMPP and is effected when a
user sends a message stanza 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).
Information regarding the syntax of message stanzas and their defined
attributes and child elements may be found in XMPP Core [1].
3.1 Specifying an Intended Recipient
An IM 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 complete address rather
than merely unless the sender has knowledge (via
presence) that the intended recipient 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 MAY include a message type in order to capture
the conversational context of the message, thus providing a hint
regarding presentation (e.g., in a GUI). If no 'type' attribute is
provided, the message SHOULD be assumed to be a standalone message to
which the recipient MAY reply if desired. 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 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
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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 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.
Although the 'type' attribute is OPTIONAL, 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 main content of the message. The contents of the body
MUST be XML character data and MUST NOT contain mixed content. If it
is necessary to provide the main message content in an alternate form
(e.g., encrypted using the public key infrastructure or formatted
using XHTML), the alternate form MUST be contained in some other
child of the message stanza. Multiple elements MAY be
included, as long as each such element possesses an 'xml:lang'
attribute with a distinct value.
A message with a body:
I implore you!
DA;pěnlivě 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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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, in general 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.)
Information regarding the syntax of presence stanzas and their
defined attributes and child elements may be found in XMPP Core [1].
4.1 Client and Server Responsibilities
When a client connects to its server, it SHOULD send an initial
presence stanza to the server in order to signal its availability for
communications. The initial presence stanza MUST possess no 'to'
address (signalling that it is meant to be handled by the server on
behalf of the user) and SHOULD possess no 'type' attribute.
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
(user@domain/resource) of the user to the bare JID (user@domain)
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 (user@domain/
resource) of the user to the bare JID (user@domain) 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 do one of the following:
1. If the username specified in the 'to' address of the presence
probe does not exist, return an error to the
user.
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2. Else if the user is not in the contact's roster with a
subscription state of "from" or "both", return a
stanza error to the user.
3. Else if the contact has no active sessions, return a
error to the user.
4. Else if the contact has blocked outbound presence notifications
to the user's bare or full JID (as defined in Section 8.11),
return a error to the user.
5. Else 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.
Upon receiving initial presence from the user, the contact's server
MUST do one of the following:
1. If the username specified in the 'to' address does not exist,
return an error to the user.
2. Else if the user is not in the contact's roster with a
subscription state of "to" or "both", return a
stanza error to the user.
3. Else if the contact has no active sessions, return a
error to the user.
4. Else if the contact has blocked inbound presence notifications
from the user's bare or full JID (as defined in Section 8.10),
return a error to the user.
5. Else deliver the user's presence stanza to the full JIDs
(contact@domain/resource) associated with all of the contact's
active sessions (subject to privacy rules).
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 successfully sends subsequent presence
information to that contact, whether or not in response to a presence
probe from the contact).
After sending initial presence, the user MAY update and broadcast its
presence information at any point 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
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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 that are in the user's
roster with a subscription type of "from" or "both" and 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 that are in the user's roster with a
subscription type of "from" or "both" and from whom the server has
not received a presence error during the user's session, as well as
to any entities to which the user has sent directed presence during
the user's session.
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
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 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.
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 is
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explicitly of type unavailable (optionally, final presence 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 a connected 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, the user's server MUST broadcast
unavailable presence to all contacts that are in the user's roster
with a subscription type of "from" or "both" and from whom the server
has not received a presence error during the session, as well as to
any entities to which the user has sent directed presence during the
user's session for that resource.
4.2 Specifying Availability Status
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").
Availability status:
away
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
client's current availability status.
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Detailed status information:
dnd
Busy fighting the Romans
4.4 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 (user@domain)
containing an empty element scoped by the 'jabber:iq:last'
namespace:
Requesting the last active time of a 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 (if the user is online and available, the 'seconds' attribute
should be set to a value of "0", i.e., zero):
Returning the last active time of a 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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Requester is forbidden to view the last active time of a user:
4.5 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@shakespeare.lit (subscription="from")
Example 1: User sends initial presence:
Example 2: User's server sends presence probe to contacts with
subscription="to" and subscription="both" on behalf of the user's
connected resource:
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Example 3: User's server sends initial presence to contacts with
subscription="from" and subscription="both" on behalf of the user's
connected resource:
Example 4: Contacts' servers reply to presence probe on behalf of all
of the contacts' connected resources:
away
be right back
0
1
dnd
gallivanting
2
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Example 5: Contacts' servers deliver user's initial presence to all
of the contacts' connected resources or returns error to user:
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
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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:
Example 10: Unavailable presence information is delivered from
contact to user:
Example 11: User sends final presence:
gone home
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Example 12: Unavailable presence information is delivered to
contact's one remaining resource as well as to the other 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".
Sending a subscription request:
If the subscription request is being sent another IM user, the JID
supplied in the 'to' attribute SHOULD be of the form
rather than .
5.2 Handling a Subscription Request
When a client receives a subscription request from another entity, it
MAY accept the request by sending a presence stanza of type
"subscribed" or decline the request by sending a presence stanza of
type "unsubscribed".
Accepting a subscription request:
Denying a presence subscription request:
A user's server MUST NOT automatically accept subscription requests
on the user's behalf. All subscription requests MUST be directed to
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the user's client. If there is no connected 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.
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".
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".
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 of the form "contact@domain". 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 connected 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 MAY 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 OPTIONAL). If a connected resource does not
request the roster during a session, it SHOULD never receive presence
subscriptions and associated roster pushes.
Client requests current roster from server:
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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.
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) IM user.
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The server MUST update the roster information in persistent storage,
and also push the change out to all connected resources associated
with the user using an IQ stanza of type "set" (this is referred to
as a "roster push"). This "roster push" enables all connected
resources to remain in sync with the server-based roster information.
Server replies with an IQ result to the sending resource and pushes
the updated roster information to all connected resources:
-
Servants
-
Servants
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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
roster item in an IQ set to the server.
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 connected resources associated with
the user.
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).
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Client removes an item:
-
Servants
As with adding a roster item, when deleting a roster item the server
MUST update the roster information in persistent storage, and also
initiate a "roster push" to all connected resources associated with
the user.
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 instant messaging users. 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. The
details regarding how these subscription states interact with roster
items are explained in the following sub-sections.
As noted above, if a connected resource does not request the roster
during a session, it SHOULD never receive presence subscriptions and
the associated roster pushes. In addition, a client MUST acknowledge
each "roster push" with an IQ stanza of type "result" (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
subscription, the user's client SHOULD send an IQ stanza of
type='set' in the 'jabber:iq:roster' namespace for the new roster
item; the element MUST possess a 'jid' attribute, MAY
possess a 'name' attribute, MAY contain one or more
child, and MUST NOT posses a 'subscription' attribute:
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2. The server then MUST (1) reply with an IQ stanza of type='result'
and (2) initiate a "roster push" for the new roster item to all
connected resources associated with this user, setting the
subscription state set to 'none':
3. In order to initiate the subscription, the user's client MUST
then send a presence stanza of type='subscribe' to the contact:
4. The server MUST then initiate a second "roster push" to all
connected resources associated with the user, setting the contact
to the pending sub-state of the 'none' subscription state; this
pending sub-state is denoted by the inclusion of the
ask='subscribe' attribute in the roster item:
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Note: if the user did not create a roster item before sending the
subscription request, the server MUST now create one and send the
above "roster push" to all of the user's connected resources.
5. The server MUST also deliver the presence stanza to the contact
or route it to the contact's server for delivery to the contact,
first stamping the stanza with the user's bare JID (i.e.,
) as the 'from' address:
6. If the contact is online (i.e., there is a connected resource
associated with the contact's account), the contact must now
decide whether or not to accept the subscription request. (If the
contact is offline, the contact's server MUST store the
subscription request offline for delivery when the contact next
becomes available.) Here we will assume the "happy path" that the
contact accepts the subscription request (the alternate flow of
declining the subscription request is defined in Section 7.2.1).
In this case, the contact's client MAY send a roster set to the
server specifying the desired nickname and group for the user,
and MUST send a presence stanza of type='subscribed' to the user
in order to accept the subscription request.
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7. The contact's server MUST now initiate a "roster push" to all
connected resources associated with the contact, containing a
roster item for the user with the subscription state set to
'from':
8. As a result of the fact that the contact has accepted the
subscription request, the user's server MUST (1) deliver the
presence stanza of type='subscribed' from the contact to the
user, and (2) initiate a "roster push" to all connected resources
associated with the user, containing an updated roster item for
the contact with the 'subscription' attribute set to a value of
"to":
From the perspective of the user, there is now a subscription to the
contact; from the perspective of the contact, there is now a
subscription from the user. The contact's server MUST now send the
contact's current presence information to 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 and not send it on
the contact.)
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
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occurs if the contact denies the user's subscription request; in
order to deny the request, the contact's client MUST send a presence
stanza of type "unsubscribed" to the user:
The user's server MUST then (1) deliver that presence stanza to the
user and (2) initiate a "roster push" to all connected resources
associated with the user, with the 'subscription' attribute set to a
value of "none":
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
defined below.
1. If the contact desires a mutual subscription, the contact MUST
send a subscription request to the user (subject to user
preferences, the contact's client MAY send this automatically):
2. The contact's server MUST then initiate a "roster push" to all
connected resources associated with the contact, 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:
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3. If the user is online (i.e., there is a connected resource
associated with the user's account), the user must now decide
whether or not to accept the subscription request. (If the user
is offline, the user's server MUST store the subscription request
offline for delivery when the user next becomes available.) Here
we will 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 case,
the user's client MUST send a presence stanza of
type='subscribed' to the contact in order to accept the
subscription request.
4. The user's server MUST then initiate a "roster push" to all
connected resources associated with the user, containing a roster
item for the contact with the 'subscription' attribute set to a
value of "both":
5. As a result of the fact that the user has accepted the
subscription request, the contact's server MUST (1) deliver the
presence stanza of type='subscribed' from the user to the
contact, and (2) initiate a "roster push" to all connected
resources associated with the contact, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "both":
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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 send it on 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; in
order to deny the request, the user's client MUST send a presence
stanza of type "unsubscribed" to the contact:
The contact's server MUST then (1) deliver that presence stanza to
the contact and (2) initiate a "roster push" to all connected
resources associated with the contact, with the 'subscription'
attribute set to a value of "from" and with no 'ask' attribute:
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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 is sent. Both possible scenarios are defined
below.
7.4.1 Case #1: Subscription Type 'to'
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. In order 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 MUST send a "roster push" to each
connected resource associated with the user, containing a roster
item for the contact with the 'subscription' attribute set to a
value of "none":
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3. The user's server MUST also route the unsubscribe "command" to
the contact's server:
4. The contact's server MUST initiate a "roster push" to all
connected resources associated with the contact, containing a
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); the contact's
server SHOULD also deliver the unsubscribe command to the
contact:
5. The contact's server then MUST send unavailable presence from the
contact to the user and MAY send a presence stanza of type
"unsubscribed" to the user:
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6. As a result, the user's server MUST deliver the unavailable
presence from the user to the contact and (if received) the
presence stanza of type "unsubscribed" from the contact to the
user,
7.4.2 Case #2: Subscription Type 'both'
In the second case, the user has a subscription to the contact and
the contact also has a subscription to the user.
1. In order 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 MUST send a "roster push" to each
connected resource associated with the user, containing a roster
item for the contact with the 'subscription' attribute set to a
value of "from":
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3. The contact's server then SHOULD auto-reply on behalf of the
contact by sending a presence stanza of type "unsubscribed" to
the user; additionally, it MUST send unavailable presence from
the contact to the user:
4. The contact's server also MUST initiate a "roster push" to all
connected resources associated with the contact, containing a
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):
5. As a result, the user's server MUST (1) deliver the presence
stanza of type='unsubscribed' from the contact to the user and
(3) deliver the unavailable presence from the user to the
contact:
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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 more completely cancel a mutual
subscription and fully remove the roster item from the user's roster,
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 is sent. Both
possible scenarios are defined below.
7.5.1 Case #1: Subscription Type 'from'
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. In order 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 MUST (1) send a "roster push"
to each connected resource associated with the contact,
containing a roster item for the user with the 'subscription'
attribute set to a value of "none", and (2) send unavailable
presence from the contact to the user:
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3. The user's server MUST then initiate a "roster push" to all
connected resources associated with the user, containing a 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); additionally, it MUST also deliver
the unavailable presence from the contact to the user:
7.5.2 Case #2: Subscription Type 'both'
In the second case, the user has a subscription to the contact and
the contact also has a subscription to the user.
1. In order to cancel the user's subscription, the user MUST send a
presence stanza of type "unsubscribed" to the user:
2. As a result, the contact's server MUST (1) send a "roster push"
to each connected resource associated with the contact,
containing a roster item for the user with the 'subscription'
attribute set to a value of "to", and (2) send unavailable
presence from the contact to the user:
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3. The user's server MUST then initiate a "roster push" to all
connected resources associated with the user, containing a 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); additionally, it MUST also deliver
the unavailable presence from the contact 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 more 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 reverting the subscription state to "none", XMPP IM
includes a "shortcut" method for doing so. The process may be
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initiated by either a contact or a user no matter what the current
subscription state is, by means of sending a roster set with the
'subscription' attribute set to a value of "remove".
For example, a user may send the following XML:
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
MUST automatically cancel any existing presence subscription between
the user and the contact by sending presence stanzas of type
"unsubscribe" and "unsubscribed" from the user to the contact. As a
result of this command, the user's server must send the user a
"roster push" with the subscription state set to "none", and the
contact's server must do the same.
A contact may also send such a command, resulting in the same type of
system behavior.
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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 within the type, the
relevant action, and the place of the item in the processing order.
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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
or delete a list item with a group that is not in the user's roster,
the server MUST return to the client an error of
class "address" in the 'urn:ietf:params:xml:ns:xmpp-stanzas'
namespace.)
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 error
of class "format" in the 'urn:ietf:params:xml:ns:xmpp-stanzas'
namespace.
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
error of class "format" in the
'urn:ietf:params:xml:ns:xmpp-stanzas' namespace.)
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
error of class "format" in the 'urn:ietf:params:xml:ns:xmpp-stanzas'
namespace.
When a client updates a privacy list, it must include all of the
desired items (i.e., not a "delta").
8.2 Business Rules
The active list affects only the session/resource for which it is
activated, and only for the duration of the session. If a stanza is
addressed to a specific resource, only the active list for that
session is processed (i.e., the default list is ignored).
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.
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.
Privacy lists SHOULD be the first routing and delivery rule applied
by a server, trumping the other rules specified in Section 9.
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 .
As soon as a stanza is matched against a privacy list, the server
SHOULD appropriately handle the stanza and cease processing.
If no fall-through item is provided in a list, the fall-through
action is assumed to be "accept".
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 connected resources associated with the user's
account, as is done for rosters. If a client or user wants to
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retrieve the current privacy list information, it SHOULD request the
relevant list.
8.3 Retrieving One's Privacy Lists
Client requests names of privacy lists from server:
Server sends names of privacy lists to client, including default list
and active list:
Client requests a privacy list from server:
Server sends a privacy list to client:
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Client requests another privacy list from server:
Server sends another privacy list to client:
Client requests yet another privacy list from server:
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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; (2)
'private', which allows communications only from contacts who have a
bidirectional subscription with the user; and (3) 'special', which
allows communications only from three specific entities. The active
list currently being applied by the server is the 'private' list.
If the user attempts to retrieve a list but a list by that name does
not exist, the server MUST return an "item not found" stanza error to
the user, which SHOULD include a child element scoped
by the 'jabber:iq:privacy:error' namespace:
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Client attempts to retrieve non-existent list:
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 "bad request" stanza error to the user, which
SHOULD include a child element scoped by the
'jabber:iq:privacy:error' namespace:
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 scoped 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.
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Client requests change of active list:
The server MUST activate and apply the requested list before sending
the result back to the client.
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 "item not found" stanza
error to the user, which SHOULD include a child
element scoped by the 'jabber:iq:privacy:error' namespace:
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.
Client declines the use of active lists:
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8.5 Managing the Default List
In order to change the default list associated with an account, the
user MUST send an IQ stanza of type "set" with a element
scoped 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.
Client requests change of default list:
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 "item not found" stanza
error to the user, which SHOULD include a child
element scoped by the 'jabber:iq:privacy:error' namespace:
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.
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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 scoped 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").
Client edits a privacy list:
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 can simply renumber
all the items before submitting the list to the server.
Server acknowledges success of list edit:
In this example, the user has added one additional entity to the
"blacklist" portion of this privacy list.
8.7 Adding a New Privacy List
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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 scoped by the 'jabber:iq:privacy'
namespace that contains one empty
child elements possessing a
'name' attribute whose value is set to the list name the user would
like to remove.
Client removes a privacy list:
Server acknowledges success of list removal:
If a user attempts to remove an active list or the default list, the
server MUST return a "conflict" stanza error to the user, which
SHOULD include a child element scoped by the
'jabber:iq:privacy:error' namespace. 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 "item not found" stanza error to
the user, which SHOULD include a child element scoped
by the 'jabber:iq:privacy:error' namespace.
If the user attempts to remove more than one list in the same
request, the server MUST return a "bad request" stanza error to the
user, which SHOULD include a child element scoped
by the 'jabber:iq:privacy:error' namespace.
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.
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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.
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.
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.
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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.
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.
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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.
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.
User blocks globally:
-
As a result of creating and applying the foregoing list, the user
will not receive presence notifications from any other users.
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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 4.4), a user SHOULD block both outbound presence
and IQs in relation to any given entity.
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.
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.
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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.
User blocks globally:
-
As a result of creating and applying the foregoing list, the user
will not send presence notifications to any other users.
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.
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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.
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.
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
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with the specified subscription type.
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.
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 presence to, the
user with the specified JID.
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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 presence to, any
users in the specified roster group.
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 presence to, any
users with the specified subscription type.
User blocks globally:
As a result of creating and applying the foregoing list, the user
will not receive any communications from, nor send presence 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.
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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 error of class "recipient" in the
'urn:ietf:params:xml:ns:xmpp-stanzas' namespace, 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.
Blocked entity attempts to send IQ get:
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
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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 (usually a client) that is
connected to the server. If the server receives a presence stanza
with no 'to' attribute, the server MUST broadcast it to the entities
that are subscribed to a user's presence. If the server receives an
IQ stanza of type "get" or "set" with no 'to' attribute and it
understands the namespace that scopes the content of the stanza, it
MUST process the stanza on behalf of the user who sent the stanza
(where the meaning of "process" is determined by the semantics of the
scoping namespace).
9.2 Foreign Domain
If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute does not match the hostname 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 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
in the 'to' attribute matches the hostname of the server itself and
the JID contained in the 'to' attribute is of the form or
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, the server SHOULD process the stanza as
appropriate for the stanza type; if the stanza is an IQ stanza and
the server understands the namespace that scopes the content of the
stanza, the server SHOULD process the request according to the
semantics of the scoping 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 a connected resource whose
authzid matches the full JID, the recipient's server MUST deliver
the stanza to the session that exactly matches the resource
identifier.
2. If the JID contains a resource identifier and there is no
connected resource whose authzid matches the full JID, the
recipient's server SHOULD return to the sender a
error of class "recipient" in the
'urn:ietf:params:xml:ns:xmpp-stanzas' namespace.
3. If the JID contains only a user@domain and there is at least one
connected 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 connected resource that provided the highest value for
the element; 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 a
connected 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 connected resources,
except that the server MUST NOT deliver the stanza to a
connected resource that provided a negative value for the
element; for presence probes, the server SHOULD
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reply based on the rules defined in Section 4.1.
3. For IQ stanzas, the server SHOULD deliver the stanza to all
connected resources, except that the server MUST NOT deliver
the stanza to a connected resource that provided a negative
value for the element.
4. If the JID contains only a user@domain and there are no connected
resource associated with the user (e.g., an IM user is offline),
the server MAY choose to store message stanzas and presence
subscription requests on behalf of the user and deliver the
stanza when an entity next becomes available for that user. If
offline storage is not enabled, the server MUST return to the
sender a error of class "server" in the
'urn:ietf:params:xml:ns:xmpp-stanzas' namespace. (Note well that
offline storage is not defined in XMPP since it strictly is a
matter of implementation and service provisioning.)
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10. IANA Considerations
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-12, work in progress)", May 2003.
[2] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for
Presence and Instant Messaging", 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 non-IM 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
.
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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:privacy:error
B.5 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-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.2 Changes from draft-ietf-xmpp-im-09
o Clarified rules regarding allowable JID types in rosters.
o Further clarified the semantics and routing implications of
presence priorities.
o Removed several obsolete subsections.
C.3 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.4 Changes from draft-ietf-xmpp-im-07
o Added several error cases for resource authorization and updated
relevant schema.
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C.5 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.6 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.
C.7 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.8 Changes from draft-ietf-xmpp-im-03
o Fixed order processing on privacy rules per list discussion.
o Made numerous small editorial changes.
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C.9 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.10 Changes from draft-ietf-xmpp-im-01
o Made numerous small editorial changes.
C.11 Changes from draft-ietf-xmpp-im-00
o Moved registration and authentication via jabber:iq:auth to
non-normative appendices.
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.12 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.
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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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