draft-ietf-xmpp-core-21.txt   draft-ietf-xmpp-core-22.txt 
XMPP Working Group P. Saint-Andre (ed.) XMPP Working Group P. Saint-Andre (ed.)
Internet-Draft Jabber Software Foundation Internet-Draft Jabber Software Foundation
Expires: July 6, 2004 January 6, 2004 Expires: July 20, 2004 January 20, 2004
Extensible Messaging and Presence Protocol (XMPP): Core Extensible Messaging and Presence Protocol (XMPP): Core
draft-ietf-xmpp-core-21 draft-ietf-xmpp-core-22
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
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This Internet-Draft will expire on July 6, 2004. This Internet-Draft will expire on July 20, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
This memo defines the core features of the Extensible Messaging and This memo defines the core features of the Extensible Messaging and
Presence Protocol (XMPP), a protocol for streaming Extensible Markup Presence Protocol (XMPP), a protocol for streaming Extensible Markup
Language (XML) elements in order to exchange structured information Language (XML) elements in order to exchange structured information
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presence applications that meet the requirements of RFC 2779. presence applications that meet the requirements of RFC 2779.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Generalized Architecture . . . . . . . . . . . . . . . . . . . 4 2. Generalized Architecture . . . . . . . . . . . . . . . . . . . 4
3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . . 6 3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . . 6
4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Use of SASL . . . . . . . . . . . . . . . . . . . . . . . . . 26 6. Use of SASL . . . . . . . . . . . . . . . . . . . . . . . . . 26
7. Resource Binding . . . . . . . . . . . . . . . . . . . . . . . 36 7. Resource Binding . . . . . . . . . . . . . . . . . . . . . . . 37
8. Server Dialback . . . . . . . . . . . . . . . . . . . . . . . 39 8. Server Dialback . . . . . . . . . . . . . . . . . . . . . . . 39
9. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 46 9. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 46
10. Server Rules for Handling XML Stanzas . . . . . . . . . . . . 55 10. Server Rules for Handling XML Stanzas . . . . . . . . . . . . 55
11. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . . 57 11. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . . 57
12. Core Compliance Requirements . . . . . . . . . . . . . . . . . 60 12. Core Compliance Requirements . . . . . . . . . . . . . . . . . 60
13. Internationalization Considerations . . . . . . . . . . . . . 61 13. Internationalization Considerations . . . . . . . . . . . . . 61
14. Security Considerations . . . . . . . . . . . . . . . . . . . 61 14. Security Considerations . . . . . . . . . . . . . . . . . . . 62
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 67
Normative References . . . . . . . . . . . . . . . . . . . . . 69 Normative References . . . . . . . . . . . . . . . . . . . . . 69
Informative References . . . . . . . . . . . . . . . . . . . . 71 Informative References . . . . . . . . . . . . . . . . . . . . 71
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 72 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 72
A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
B. Resourceprep . . . . . . . . . . . . . . . . . . . . . . . . . 74 B. Resourceprep . . . . . . . . . . . . . . . . . . . . . . . . . 74
C. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . . 76 C. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . . 76
D. Differences Between Core Jabber Protocol and XMPP . . . . . . 83 D. Differences Between Core Jabber Protocol and XMPP . . . . . . 84
E. Revision History . . . . . . . . . . . . . . . . . . . . . . . 85 E. Revision History . . . . . . . . . . . . . . . . . . . . . . . 85
Intellectual Property and Copyright Statements . . . . . . . . 94 Intellectual Property and Copyright Statements . . . . . . . . 95
1. Introduction 1. Introduction
1.1 Overview 1.1 Overview
The Extensible Messaging and Presence Protocol (XMPP) is an open XML The Extensible Messaging and Presence Protocol (XMPP) is an open XML
[XML] protocol for near-real-time messaging, presence, and [XML] protocol for near-real-time messaging, presence, and
request-response services. The basic syntax and semantics were request-response services. The basic syntax and semantics were
developed originally within the Jabber open-source community, mainly developed originally within the Jabber open-source community, mainly
in 1999. In 2002, the XMPP WG was chartered with developing an in 1999. In 2002, the XMPP WG was chartered with developing an
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stringprep profiles were originally contributed by Joe Hildebrand. stringprep profiles were originally contributed by Joe Hildebrand.
The error code syntax was suggested by Lisa Dusseault. The error code syntax was suggested by Lisa Dusseault.
1.4 Acknowledgements 1.4 Acknowledgements
Thanks are due to a number of individuals in addition to the Thanks are due to a number of individuals in addition to the
contributors listed. Although it is difficult to provide a complete contributors listed. Although it is difficult to provide a complete
list, the following individuals were particularly helpful in defining list, the following individuals were particularly helpful in defining
the protocols or in commenting on the specifications in this memo: the protocols or in commenting on the specifications in this memo:
Thomas Charron, Richard Dobson, Sam Hartman, Schuyler Heath, Jonathan Thomas Charron, Richard Dobson, Sam Hartman, Schuyler Heath, Jonathan
Hogg, Craig Kaes, Jacek Konieczny, Alexey Melnikov, Keith Minkler, Hogg, Cullen Jennings, Craig Kaes, Jacek Konieczny, Alexey Melnikov,
Julian Missig, Pete Resnick, Marshall Rose, Alexey Shchepin, Keith Minkler, Julian Missig, Pete Resnick, Marshall Rose, Alexey
Jean-Louis Seguineau, Iain Shigeoka, and David Waite. Thanks also to Shchepin, Jean-Louis Seguineau, Iain Shigeoka, Greg Troxel, and David
members of the XMPP Working Group and the IETF community for comments Waite. Thanks also to members of the XMPP Working Group and the IETF
and feedback provided throughout the life of this memo. community for comments and feedback provided throughout the life of
this memo.
2. Generalized Architecture 2. Generalized Architecture
2.1 Overview 2.1 Overview
Although XMPP is not wedded to any specific network architecture, to Although XMPP is not wedded to any specific network architecture, to
date it usually has been implemented via a typical client-server date it usually has been implemented via a typical client-server
architecture, wherein a client utilizing XMPP accesses a server over architecture, wherein a client utilizing XMPP accesses a server over
a TCP [TCP] socket. a TCP [TCP] connection.
The following diagram provides a high-level overview of this The following diagram provides a high-level overview of this
architecture (where "-" represents communications that use XMPP and architecture (where "-" represents communications that use XMPP and
"=" represents communications that use any other protocol). "=" represents communications that use any other protocol).
C1 - S1 - S2 - C3 C1 - S1 - S2 - C3
/ \ / \
C2 - G1 = FN1 = FC1 C2 - G1 = FN1 = FC1
The symbols are as follows: The symbols are as follows:
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such entities over XML streams such entities over XML streams
Most XMPP-compliant servers also assume responsibility for the Most XMPP-compliant servers also assume responsibility for the
storage of data that is used by clients (e.g., contact lists for storage of data that is used by clients (e.g., contact lists for
users of XMPP-based instant messaging and presence applications); in users of XMPP-based instant messaging and presence applications); in
this case, the XML data is processed directly by the server itself on this case, the XML data is processed directly by the server itself on
behalf of the client and is not routed to another entity. behalf of the client and is not routed to another entity.
2.3 Client 2.3 Client
Most clients connect directly to a server over a [TCP] socket and use Most clients connect directly to a server over a [TCP] connection and
XMPP to take full advantage of the functionality provided by a server use XMPP to take full advantage of the functionality provided by a
and any associated services. Although there is no necessary coupling server and any associated services. Although there is no necessary
of an XML stream to a TCP socket (e.g., a client could connect via coupling of an XML stream to a TCP connection (e.g., a client could
HTTP [HTTP] polling or some other mechanism), this specification connect via HTTP [HTTP] polling or some other mechanism), this
defines a binding of XMPP to TCP only. Multiple resources (e.g., specification defines a binding of XMPP to TCP only. Multiple
devices or locations) MAY connect simultaneously to a server on resources (e.g., devices or locations) MAY connect simultaneously to
behalf of each authorized client, with each resource differentiated a server on behalf of each authorized client, with each resource
by the resource identifier of an XMPP address (e.g., <node@domain/ differentiated by the resource identifier of an XMPP address (e.g.,
home> vs. <node@domain/work>) as defined under Addressing Scheme <node@domain/home> vs. <node@domain/work>) as defined under
(Section 3). The RECOMMENDED port for connections between a client Addressing Scheme (Section 3). The RECOMMENDED port for connections
and a server is 5222, as registered with the IANA (see Port Numbers between a client and a server is 5222, as registered with the IANA
(Section 15.9)). (see Port Numbers (Section 15.9)).
2.4 Gateway 2.4 Gateway
A gateway is a special-purpose server-side service whose primary A gateway is a special-purpose server-side service whose primary
function is to translate XMPP into the protocol used by a foreign function is to translate XMPP into the protocol used by a foreign
(non-XMPP) messaging system, as well as to translate the return data (non-XMPP) messaging system, as well as to translate the return data
back into XMPP. Examples are gateways to Internet Relay Chat (IRC), back into XMPP. Examples are gateways to Internet Relay Chat (IRC),
Short Message Service (SMS), SIMPLE, SMTP, and legacy instant Short Message Service (SMS), SIMPLE, SMTP, and legacy instant
messaging networks such as AIM, ICQ, MSN Messenger, and Yahoo! messaging networks such as AIM, ICQ, MSN Messenger, and Yahoo!
Instant Messenger. Communications between gateways and servers, and Instant Messenger. Communications between gateways and servers, and
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Because each server is identified by a network address and because Because each server is identified by a network address and because
server-to-server communications are a straightforward extension of server-to-server communications are a straightforward extension of
the client-to-server protocol, in practice the system consists of a the client-to-server protocol, in practice the system consists of a
network of servers that inter-communicate. Thus user-a@domain1 is network of servers that inter-communicate. Thus user-a@domain1 is
able to exchange messages, presence, and other information with able to exchange messages, presence, and other information with
user-b@domain2. This pattern is familiar from messaging protocols user-b@domain2. This pattern is familiar from messaging protocols
(such as SMTP) that make use of network addressing standards. (such as SMTP) that make use of network addressing standards.
Communications between any two servers are OPTIONAL. If enabled, Communications between any two servers are OPTIONAL. If enabled,
such communications SHOULD occur over XML streams that are bound to such communications SHOULD occur over XML streams that are bound to
[TCP] sockets. The RECOMMENDED port for connections between servers [TCP] connections. The RECOMMENDED port for connections between
is 5269, as registered with the IANA (see Port Numbers (Section servers is 5269, as registered with the IANA (see Port Numbers
15.9)). (Section 15.9)).
3. Addressing Scheme 3. Addressing Scheme
3.1 Overview 3.1 Overview
An entity is anything that can be considered a network endpoint An entity is anything that can be considered a network endpoint
(i.e., an ID on the network) and that can communicate using XMPP. (i.e., an ID on the network) and that can communicate using XMPP.
All such entities are uniquely addressable in a form that is All such entities are uniquely addressable in a form that is
consistent with RFC 2396 [URI]. For historical reasons, the address consistent with RFC 2396 [URI]. For historical reasons, the address
of an XMPP entity is called a Jabber Identifier or JID. A valid JID of an XMPP entity is called a Jabber Identifier or JID. A valid JID
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Two fundamental concepts make possible the rapid, asynchronous Two fundamental concepts make possible the rapid, asynchronous
exchange of relatively small payloads of structured information exchange of relatively small payloads of structured information
between presence-aware entities: XML streams and XML stanzas. These between presence-aware entities: XML streams and XML stanzas. These
terms are defined as follows: terms are defined as follows:
Definition of XML Stream: An XML stream is a container for the Definition of XML Stream: An XML stream is a container for the
exchange of XML elements between any two entities over a network. exchange of XML elements between any two entities over a network.
An XML stream is negotiated from an initiating entity (usually a An XML stream is negotiated from an initiating entity (usually a
client or server) to a receiving entity (usually a server), client or server) to a receiving entity (usually a server),
normally over a [TCP] socket, and corresponds to the initiating normally over a [TCP] connection, and corresponds to the
entity's "session" with the receiving entity. The start of the initiating entity's "session" with the receiving entity. The
XML stream is denoted unambiguously by an opening XML <stream> tag start of the XML stream is denoted unambiguously by an opening XML
(with appropriate attributes and namespace declarations), while <stream> tag (with appropriate attributes and namespace
the end of the XML stream is denoted unambiguously by a closing declarations), while the end of the XML stream is denoted
XML </stream> tag. An XML stream is unidirectional; in order to unambiguously by a closing XML </stream> tag. An XML stream is
enable bidirectional information exchange, the initiating entity unidirectional; in order to enable bidirectional information
and receiving entity MUST negotiate one stream in each direction exchange, the initiating entity and receiving entity MUST
(the "initial stream" and the "response stream"), normally over negotiate one stream in each direction (the "initial stream" and
the same TCP connection. the "response stream"), normally over the same TCP connection.
Definition of XML Stanza: An XML stanza is a discrete semantic unit Definition of XML Stanza: An XML stanza is a discrete semantic unit
of structured information that is sent from one entity to another of structured information that is sent from one entity to another
over an XML stream. An XML stanza exists at the direct child over an XML stream. An XML stanza exists at the direct child
level of the root <stream/> element and is said to be level of the root <stream/> element and is said to be
well-balanced if it matches production [43] content of [XML]. The well-balanced if it matches production [43] content of [XML]. The
start of any XML stanza is denoted unambiguously by the element start of any XML stanza is denoted unambiguously by the element
start tag at depth=1 of the XML stream (e.g., <presence>), and the start tag at depth=1 of the XML stream (e.g., <presence>), and the
end of any XML stanza is denoted unambiguously by the end of any XML stanza is denoted unambiguously by the
corresponding close tag at depth=1 (e.g., </presence>). An XML corresponding close tag at depth=1 (e.g., </presence>). An XML
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entity to the receiving entity; however, if a 'from' attribute is entity to the receiving entity; however, if a 'from' attribute is
included, it SHOULD be silently ignored by the receiving entity. included, it SHOULD be silently ignored by the receiving entity.
o id -- The 'id' attribute SHOULD be used only in the XML stream o id -- The 'id' attribute SHOULD be used only in the XML stream
header from the receiving entity to the initiating entity. This header from the receiving entity to the initiating entity. This
attribute is a unique identifier created by the receiving entity attribute is a unique identifier created by the receiving entity
to function as a session key for the initiating entity's streams to function as a session key for the initiating entity's streams
with the receiving entity, and MUST be unique within the receiving with the receiving entity, and MUST be unique within the receiving
application (normally a server). Note well that the stream ID may application (normally a server). Note well that the stream ID may
be security-critical and therefore MUST be both unpredictable and be security-critical and therefore MUST be both unpredictable and
non-repeating. There SHOULD be no 'id' attribute on the XML nonrepeating (see [RANDOM] for recommendations regarding
stream header sent from the initiating entity to the receiving randomness for security purposes). There SHOULD be no 'id'
entity; however, if an 'id' attribute is included, it SHOULD be attribute on the XML stream header sent from the initiating entity
silently ignored by the receiving entity. to the receiving entity; however, if an 'id' attribute is
included, it SHOULD be silently ignored by the receiving entity.
o xml:lang -- An 'xml:lang' attribute (as defined in Section 2.12 of o xml:lang -- An 'xml:lang' attribute (as defined in Section 2.12 of
[XML]) SHOULD be included by the initiating entity on the header [XML]) SHOULD be included by the initiating entity on the header
for the initial stream to specify the default language of any for the initial stream to specify the default language of any
human-readable XML character data it sends over that stream. If human-readable XML character data it sends over that stream. If
the attribute is included, the receiving entity SHOULD remember the attribute is included, the receiving entity SHOULD remember
that value as the default for both the initial stream and the that value as the default for both the initial stream and the
response stream; if the attribute is not included, the receiving response stream; if the attribute is not included, the receiving
entity SHOULD use a configurable default value for both streams, entity SHOULD use a configurable default value for both streams,
which it MUST communicate in the header for the response stream. which it MUST communicate in the header for the response stream.
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id | silently ignored | session key id | silently ignored | session key
xml:lang | default language | default language xml:lang | default language | default language
version | signals XMPP 1.0 support | signals XMPP 1.0 support version | signals XMPP 1.0 support | signals XMPP 1.0 support
4.2.1 Version Support 4.2.1 Version Support
The version of XMPP specified herein is "1.0"; in particular, this The version of XMPP specified herein is "1.0"; in particular, this
encapsulates the stream-related protocols (Use of TLS (Section 5), encapsulates the stream-related protocols (Use of TLS (Section 5),
Use of SASL (Section 6), and Stream Errors (Section 4.6)) as well as Use of SASL (Section 6), and Stream Errors (Section 4.6)) as well as
the semantics of the three defined XML stanza types (<message/>, the semantics of the three defined XML stanza types (<message/>,
<presence/>, and <iq/>). The major version number should be <presence/>, and <iq/>). The numbering scheme for XMPP versions is
incremented only if the stream and stanza formats or required actions "<major>.<minor>". The major and minor numbers MUST be treated as
have changed so dramatically that an older version entity would not separate integers and each number MAY be incremented higher than a
be able to interoperate with a newer version entity if it simply single digit. Thus, "XMPP 2.4" would be a lower version than "XMPP
ignored the elements and attributes it did not understand and took 2.13", which in turn would be lower than "XMPP 12.3". Leading zeros
the actions specified in the older specification. The minor version (e.g., "XMPP 6.01") MUST be ignored by recipients and MUST NOT be
number indicates new capabilities, and MUST be ignored by an entity sent.
with a smaller minor version number, but used for informational
purposes by the node with the larger minor version number. For The major version number should be incremented only if the stream and
example, a minor version number might indicate the ability to process stanza formats or required actions have changed so dramatically that
a newly defined value of the 'type' attribute for message, presence, an older version entity would not be able to interoperate with a
or IQ stanzas; the node with the larger minor version number would newer version entity if it simply ignored the elements and attributes
simply note that its correspondent would not be able to understand it did not understand and took the actions specified in the older
that value of the 'type' attribute and therefore would not send it. specification. The minor version number indicates new capabilities,
and MUST be ignored by an entity with a smaller minor version number,
but used for informational purposes by the node with the larger minor
version number. For example, a minor version number might indicate
the ability to process a newly defined value of the 'type' attribute
for message, presence, or IQ stanzas; the node with the larger minor
version number would simply note that its correspondent would not be
able to understand that value of the 'type' attribute and therefore
would not send it.
The following rules apply to the generation and handling by The following rules apply to the generation and handling by
implementations of the 'version' attribute within stream headers: implementations of the 'version' attribute within stream headers:
1. The initiating entity MUST set the value of the 'version' 1. The initiating entity MUST set the value of the 'version'
attribute on the initial stream header to the highest version attribute on the initial stream header to the highest version
number it supports (e.g., if the highest version number it number it supports (e.g., if the highest version number it
supports is that defined in this specification, it MUST set the supports is that defined in this specification, it MUST set the
value to "1.0"). value to "1.0").
2. The receiving entity MUST set the value of the 'version' 2. The receiving entity MUST set the value of the 'version'
attribute on the response stream header to either the value attribute on the response stream header to either the value
supplied by the initiating entity or highest version number supplied by the initiating entity or highest version number
supported by the receiving entity, whichever is lower. The supported by the receiving entity, whichever is lower. The
receiving entity MUST perform a numeric comparison, not a string receiving entity MUST perform a numeric comparison on the major
match. and minor version numbers, not a string match on
"<major>.<minor>".
3. If the version number included in the response stream header is 3. If the version number included in the response stream header is
at least one major version lower than the version number included at least one major version lower than the version number included
in the initial stream header and newer version entities cannot in the initial stream header and newer version entities cannot
interoperate with older version entities as described above, the interoperate with older version entities as described above, the
initiating entity SHOULD generate an <unsupported-version/> initiating entity SHOULD generate an <unsupported-version/>
stream error and terminate the XML stream and underlying TCP stream error and terminate the XML stream and underlying TCP
connection. connection.
4. If either entity receives a stream header with no 'version' 4. If either entity receives a stream header with no 'version'
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</text> </text>
[OPTIONAL application-specific condition element] [OPTIONAL application-specific condition element]
</stream:error> </stream:error>
The <error/> element: The <error/> element:
o MUST contain a child element corresponding to one of the defined o MUST contain a child element corresponding to one of the defined
stanza error conditions defined below; this element MUST be stanza error conditions defined below; this element MUST be
qualified by the 'urn:ietf:params:xml:ns:xmpp-streams' namespace qualified by the 'urn:ietf:params:xml:ns:xmpp-streams' namespace
o MAY contain a <text/> child containing CDATA that describes the o MAY contain a <text/> child containing XML character data that
error in more detail; this element MUST be qualified by the describes the error in more detail; this element MUST be qualified
'urn:ietf:params:xml:ns:xmpp-streams' namespace and SHOULD possess by the 'urn:ietf:params:xml:ns:xmpp-streams' namespace and SHOULD
an 'xml:lang' attribute possess an 'xml:lang' attribute specifying the natural language of
the XML character data
o MAY contain a child element for an application-specific error o MAY contain a child element for an application-specific error
condition; this element MUST be qualified by an condition; this element MUST be qualified by an
application-defined namespace, and its structure is defined by application-defined namespace, and its structure is defined by
that namespace that namespace
The <text/> element is OPTIONAL. If included, it SHOULD be used only The <text/> element is OPTIONAL. If included, it SHOULD be used only
to provide descriptive or diagnostic information that supplements the to provide descriptive or diagnostic information that supplements the
meaning of a defined condition or application-specific condition. It meaning of a defined condition or application-specific condition. It
SHOULD NOT be interpreted programmatically by an application. It SHOULD NOT be interpreted programmatically by an application. It
SHOULD NOT be used as the error message presented to a user, but MAY SHOULD NOT be used as the error message presented to a user, but MAY
be shown in addition to the error message associated with the be shown in addition to the error message associated with the
included condition element (or elements). included condition element (or elements).
4.6.3 Defined Conditions 4.6.3 Defined Conditions
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negotiation to have begun immediately after receiving the negotiation to have begun immediately after receiving the
closing ">" character of the <proceed/> element from the closing ">" character of the <proceed/> element from the
receiving entity. receiving entity.
7. The initiating entity MUST validate the certificate presented by 7. The initiating entity MUST validate the certificate presented by
the receiving entity; see Certificate Validation (Section 14.2) the receiving entity; see Certificate Validation (Section 14.2)
regarding certificate validation procedures. regarding certificate validation procedures.
8. Certificates MUST be checked against the hostname as provided by 8. Certificates MUST be checked against the hostname as provided by
the initiating entity (e.g., a user), not the hostname as the initiating entity (e.g., a user), not the hostname as
resolved via the Domain Name System; e.g., if the user or resolved via the Domain Name System; e.g., if the user specifies
certificate specifies a hostname of "example.com" but a DNS SRV a hostname of "example.com" but a DNS SRV [SRV] lookup returned
[SRV] lookup returned "im.example.com", the certificate MUST be "im.example.com", the certificate MUST be checked as
checked as "example.com". If a JID is represented in a "example.com". If a JID for any kind of XMPP entity (e.g.,
certificate, it SHOULD be encoded using the otherName choice of client or server) is represented in a certificate, it SHOULD be
the subjectAltName type along with a type-id of "xmpp" (as these encoded as a GeneralName entry of type otherName inside the
terms are profiled in [X509]). subjectAltName, along with a type-id whose value is "xmpp" (as
these terms are profiled in [X509]).
9. Certificates MUST be checked against the hostname as provided by
the initiating entity (e.g., a user), not the hostname as
resolved via the Domain Name System; e.g., if the user or
certificate specifies a hostname of "example.com" but a DNS SRV
[SRV] lookup returned "im.example.com", the certificate MUST be
checked as "example.com". If a JID is represented in a
certificate, it SHOULD be encoded using the otherName choice of
the subjectAltName type along with a type-id of "xmpp" (as these
terms are profiled in [X509]).
10. If the TLS negotiation is successful, the receiving entity MUST 9. If the TLS negotiation is successful, the receiving entity MUST
discard any knowledge obtained in an insecure manner from the discard any knowledge obtained in an insecure manner from the
initiating entity before TLS takes effect. initiating entity before TLS takes effect.
11. If the TLS negotiation is successful, the initiating entity MUST 10. If the TLS negotiation is successful, the initiating entity MUST
discard any knowledge obtained in an insecure manner from the discard any knowledge obtained in an insecure manner from the
receiving entity before TLS takes effect. receiving entity before TLS takes effect.
12. If the TLS negotiation is successful, the receiving entity MUST 11. If the TLS negotiation is successful, the receiving entity MUST
NOT offer the STARTTLS extension to the initiating entity along NOT offer the STARTTLS extension to the initiating entity along
with the other stream features that are offered when the stream with the other stream features that are offered when the stream
is restarted. is restarted.
13. If the TLS negotiation is successful, the initiating entity MUST 12. If the TLS negotiation is successful, the initiating entity MUST
continue with SASL negotiation. continue with SASL negotiation.
14. If the TLS negotiation results in failure, the receiving entity 13. If the TLS negotiation results in failure, the receiving entity
MUST terminate both the XML stream and the underlying TCP MUST terminate both the XML stream and the underlying TCP
connection. connection.
15. See Mandatory-to-Implement Technologies (Section 14.7) regarding 14. See Mandatory-to-Implement Technologies (Section 14.7) regarding
mechanisms that MUST be supported. mechanisms that MUST be supported.
5.2 Narrative 5.2 Narrative
When an initiating entity secures a stream with a receiving entity, When an initiating entity secures a stream with a receiving entity,
the steps involved are as follows: the steps involved are as follows:
1. The initiating entity opens a TCP connection and initiates the 1. The initiating entity opens a TCP connection and initiates the
stream by sending the opening XML stream header to the receiving stream by sending the opening XML stream header to the receiving
entity, including the 'version' attribute set to a value of entity, including the 'version' attribute set to a value of
skipping to change at page 1, line 1042 skipping to change at page 23, line 24
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism> <mechanism>DIGEST-MD5</mechanism>
<mechanism>PLAIN</mechanism> <mechanism>PLAIN</mechanism>
</mechanisms> </mechanisms>
</stream:features> </stream:features>
Step 4: Client sends the STARTTLS command to server: Step 4: Client sends the STARTTLS command to server:
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> <starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5: Server informs client to proceed: Step 5: Server informs client that it is allowed to proceed:
<proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> <proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5 (alt): Server informs client that TLS negotiation has failed Step 5 (alt): Server informs client that TLS negotiation has failed
and closes both stream and TCP connection: and closes both stream and TCP connection:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> <failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
</stream:stream> </stream:stream>
Step 6: Client and server attempt to complete TLS negotiation over Step 6: Client and server attempt to complete TLS negotiation over
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<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism> <mechanism>DIGEST-MD5</mechanism>
<mechanism>KERBEROS_V4</mechanism> <mechanism>KERBEROS_V4</mechanism>
</mechanisms> </mechanisms>
</stream:features> </stream:features>
Step 4: Server1 sends the STARTTLS command to Server2: Step 4: Server1 sends the STARTTLS command to Server2:
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> <starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5: Server2 informs Server1 to proceed: Step 5: Server2 informs Server1 that it is allowed to proceed:
<proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> <proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5 (alt): Server2 informs Server1 that TLS negotiation has failed Step 5 (alt): Server2 informs Server1 that TLS negotiation has failed
and closes stream: and closes stream:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> <failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
</stream:stream> </stream:stream>
Step 6: Server1 and Server2 attempt to complete TLS negotiation via Step 6: Server1 and Server2 attempt to complete TLS negotiation via
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5. Any character data contained within the XML elements used during 5. Any character data contained within the XML elements used during
SASL negotiation MUST be encoded using base64, where the SASL negotiation MUST be encoded using base64, where the
encoding adheres to the definition in Section 3 of RFC 3548 encoding adheres to the definition in Section 3 of RFC 3548
[BASE64]. [BASE64].
6. If provision of a "simple username" is supported by the selected 6. If provision of a "simple username" is supported by the selected
SASL mechanism (e.g., this is supported by the DIGEST-MD5 and SASL mechanism (e.g., this is supported by the DIGEST-MD5 and
CRAM-MD5 mechanisms but not by the EXTERNAL and GSSAPI CRAM-MD5 mechanisms but not by the EXTERNAL and GSSAPI
mechanisms), during authentication the initiating entity SHOULD mechanisms), during authentication the initiating entity SHOULD
provide its sending domain (in the case of server-to-server provide as the simple username its sending domain (IP address or
communications) or registered account name (in the case of fully qualified domain name as contained in a domain identifier)
client-to-server communications) as the simple username. in the case of server-to-server communications or its registered
account name (user or node name as contained in an XMPP node
identifer) in the case of client-to-server communications.
7. If the initiating entity wishes to act on behalf of another 7. If the initiating entity wishes to act on behalf of another
entity and the selected SASL mechanism supports transmission of entity and the selected SASL mechanism supports transmission of
an authorization identity, the initiating entity MUST provide an an authorization identity, the initiating entity MUST provide an
authorization identity during SASL negotiation. If the authorization identity during SASL negotiation. If the
initiating entity does not wish to act on behalf of another initiating entity does not wish to act on behalf of another
entity, it MUST NOT provide an authorization identity. As entity, it MUST NOT provide an authorization identity. As
specified in [SASL], the initiating entity MUST NOT provide an specified in [SASL], the initiating entity MUST NOT provide an
authorization identity unless the authorization identity is authorization identity unless the authorization identity is
different from the default authorization identity derived from different from the default authorization identity derived from
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connected resource as determined by the server: connected resource as determined by the server:
Server informs client of successful resource binding: Server informs client of successful resource binding:
<iq type='result' id='bind_2'> <iq type='result' id='bind_2'>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'> <bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'>
<jid>somenode@example.com/someresource</jid> <jid>somenode@example.com/someresource</jid>
</bind> </bind>
</iq> </iq>
A server is NOT REQUIRED to accept the resource identifier provided A server SHOULD accept the resource identifier provided by the
by the client, and MAY override it with a resource identifier that client, but MAY override it with a resource identifier that the
the server generates; in this case, the server SHOULD NOT return a server generates; in this case, the server SHOULD NOT return a stanza
stanza error (e.g., <forbidden/>) to the client but instead SHOULD error (e.g., <forbidden/>) to the client but instead SHOULD
communicate the generated resource identifier to the client in the IQ communicate the generated resource identifier to the client in the IQ
result as shown above. result as shown above.
When a client supplies a resource identifier, the following stanza When a client supplies a resource identifier, the following stanza
error conditions are possible (see Stanza Errors (Section 9.3)): error conditions are possible (see Stanza Errors (Section 9.3)):
o The provided resource identifier cannot be processed by the server o The provided resource identifier cannot be processed by the server
in accordance with Resourceprep (Appendix B). in accordance with Resourceprep (Appendix B).
o The client is not allowed to bind a resource to the stream (e.g., o The client is not allowed to bind a resource to the stream (e.g.,
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the authoritative server for a given domain. Because dialback depends the authoritative server for a given domain. Because dialback depends
on DNS, inter-domain communications MUST NOT proceed until the Domain on DNS, inter-domain communications MUST NOT proceed until the Domain
Name System (DNS) hostnames asserted by the servers have been Name System (DNS) hostnames asserted by the servers have been
resolved (see Server-to-Server Communications (Section 14.4)). resolved (see Server-to-Server Communications (Section 14.4)).
The method for generating and verifying the keys used in server The method for generating and verifying the keys used in server
dialback MUST take into account the hostnames being used, the stream dialback MUST take into account the hostnames being used, the stream
ID generated by the receiving server, and a secret known by the ID generated by the receiving server, and a secret known by the
authoritative server's network. The stream ID is security-critical in authoritative server's network. The stream ID is security-critical in
server dialback and therefore MUST be both unpredictable and server dialback and therefore MUST be both unpredictable and
non-repeating. non-repeating (see [RANDOM] for recommendations regarding randomness
for security purposes).
Any error that occurs during dialback negotiation MUST be considered Any error that occurs during dialback negotiation MUST be considered
a stream error, resulting in termination of the stream and of the a stream error, resulting in termination of the stream and of the
underlying TCP connection. The possible error conditions are underlying TCP connection. The possible error conditions are
specified in the protocol description below. specified in the protocol description below.
The following terminology applies: The following terminology applies:
o Originating Server -- the server that is attempting to establish a o Originating Server -- the server that is attempting to establish a
connection between two domains. connection between two domains.
skipping to change at page 1, line 1939 skipping to change at page 42, line 23
1. Originating Server establishes TCP connection to Receiving 1. Originating Server establishes TCP connection to Receiving
Server. Server.
2. Originating Server sends a stream header to Receiving Server: 2. Originating Server sends a stream header to Receiving Server:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback'> xmlns:db='jabber:server:dialback'>
Note: The 'to' and 'from' attributes are NOT REQUIRED on the Note: The 'to' and 'from' attributes are OPTIONAL on the root
root stream element. The inclusion of the xmlns:db namespace stream element. The inclusion of the xmlns:db namespace
declaration with the name shown indicates to Receiving Server declaration with the name shown indicates to Receiving Server
that Originating Server supports dialback. If the namespace that Originating Server supports dialback. If the namespace
name is incorrect, then Receiving Server MUST generate an name is incorrect, then Receiving Server MUST generate an
<invalid-namespace/> stream error condition and terminate both <invalid-namespace/> stream error condition and terminate both
the XML stream and the underlying TCP connection. the XML stream and the underlying TCP connection.
3. Receiving Server SHOULD send a stream header back to Originating 3. Receiving Server SHOULD send a stream header back to Originating
Server, including a unique ID for this interaction: Server, including a unique ID for this interaction:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback' xmlns:db='jabber:server:dialback'
id='457F9224A0...'> id='457F9224A0...'>
Note: The 'to' and 'from' attributes are NOT REQUIRED on the Note: The 'to' and 'from' attributes are OPTIONAL on the root
root stream element. If the namespace name is incorrect, then stream element. If the namespace name is incorrect, then
Originating Server MUST generate an <invalid-namespace/> stream Originating Server MUST generate an <invalid-namespace/> stream
error condition and terminate both the XML stream and the error condition and terminate both the XML stream and the
underlying TCP connection. Note well that Receiving Server is underlying TCP connection. Note well that Receiving Server
NOT REQUIRED to reply and MAY silently terminate the XML stream SHOULD reply but MAY silently terminate the XML stream and
and underlying TCP connection depending on security policies in underlying TCP connection depending on security policies in
place; however, if Receiving Server desires to proceed, it MUST place; however, if Receiving Server desires to proceed, it MUST
sent a stream header back to Originating Server. send a stream header back to Originating Server.
4. Originating Server sends a dialback key to Receiving Server: 4. Originating Server sends a dialback key to Receiving Server:
<db:result <db:result
to='Receiving Server' to='Receiving Server'
from='Originating Server'> from='Originating Server'>
98AF014EDC0... 98AF014EDC0...
</db:result> </db:result>
Note: This key is not examined by Receiving Server, since Note: This key is not examined by Receiving Server, since
Receiving Server does not keep information about Originating Receiving Server does not keep information about Originating
Server between sessions. The key generated by Originating Server between sessions. The key generated by Originating
Server MUST be based in part on the value of the ID provided by Server MUST be based in part on the value of the ID provided by
Receiving Server in the previous step, and in part on a secret Receiving Server in the previous step, and in part on a secret
shared by Originating Server and Authoritative Server. If the shared by Originating Server and Authoritative Server. If the
value of the 'to' address does not match a hostname recognized value of the 'to' address does not match a hostname recognized
by Receiving Server, then Receiving Server MUST generate a by Receiving Server, then Receiving Server MUST generate a
<host-unknown/> stream error condition and terminate both the <host-unknown/> stream error condition and terminate both the
XML stream and the underlying TCP connection. If the value of XML stream and the underlying TCP connection. If the value of
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implementation MAY reuse an existing trusted connection here implementation MAY reuse an existing trusted connection here
rather than opening a new TCP connection.) rather than opening a new TCP connection.)
6. Receiving Server sends Authoritative Server a stream header: 6. Receiving Server sends Authoritative Server a stream header:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback'> xmlns:db='jabber:server:dialback'>
Note: The 'to' and 'from' attributes are NOT REQUIRED on the Note: The 'to' and 'from' attributes are OPTIONAL on the root
root stream element. If the namespace name is incorrect, then stream element. If the namespace name is incorrect, then
Authoritative Server MUST generate an <invalid-namespace/> Authoritative Server MUST generate an <invalid-namespace/>
stream error condition and terminate both the XML stream and the stream error condition and terminate both the XML stream and the
underlying TCP connection. underlying TCP connection.
7. Authoritative Server sends Receiving Server a stream header: 7. Authoritative Server sends Receiving Server a stream header:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback' xmlns:db='jabber:server:dialback'
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contained in the 'from' attribute MUST match the hostname (or any contained in the 'from' attribute MUST match the hostname (or any
validated domain) of the sending server as communicated in the SASL validated domain) of the sending server as communicated in the SASL
negotiation or dialback negotiation; if a server receives a stanza negotiation or dialback negotiation; if a server receives a stanza
that does not meet this restriction, it MUST generate an that does not meet this restriction, it MUST generate an
<invalid-from/> stream error condition. Both of these conditions <invalid-from/> stream error condition. Both of these conditions
MUST result in closing of the stream and termination of the MUST result in closing of the stream and termination of the
underlying TCP connection; this helps to prevent a denial of service underlying TCP connection; this helps to prevent a denial of service
attack launched from a rogue server. attack launched from a rogue server.
9.1.3 id 9.1.3 id
The optional 'id' attribute MAY be used by a sending entity for The optional 'id' attribute MAY be used by a sending entity for
internal tracking of stanzas that it sends and receives (especially internal tracking of stanzas that it sends and receives (especially
for tracking the request-response interaction inherent in the for tracking the request-response interaction inherent in the
semantics of IQ stanzas). The value of the 'id' attribute is NOT semantics of IQ stanzas). It is OPTIONAL for the value of the 'id'
REQUIRED to be unique either globally, within a domain, or within a attribute to be unique globally, within a domain, or within a stream.
stream. The semantics of IQ stanzas impose additional restrictions; The semantics of IQ stanzas impose additional restrictions; see IQ
see IQ Semantics (Section 9.2.3). Semantics (Section 9.2.3).
9.1.4 type 9.1.4 type
The 'type' attribute specifies detailed information about the purpose The 'type' attribute specifies detailed information about the purpose
or context of the message, presence, or IQ stanza. The particular or context of the message, presence, or IQ stanza. The particular
allowable values for the 'type' attribute vary depending on whether allowable values for the 'type' attribute vary depending on whether
the stanza is a message, presence, or IQ; the values for message and the stanza is a message, presence, or IQ; the values for message and
presence stanzas are specific to instant messaging and presence presence stanzas are specific to instant messaging and presence
applications and therefore are defined in [XMPP-IM], whereas the applications and therefore are defined in [XMPP-IM], whereas the
values for IQ stanzas specify the role of an IQ stanza in a values for IQ stanzas specify the role of an IQ stanza in a
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9.3.1 Rules 9.3.1 Rules
The following rules apply to stanza-related errors: The following rules apply to stanza-related errors:
o The receiving or processing entity that detects an error condition o The receiving or processing entity that detects an error condition
in relation to a stanza MUST return to the sending entity a stanza in relation to a stanza MUST return to the sending entity a stanza
of the same kind (message, presence, or IQ) whose 'type' attribute of the same kind (message, presence, or IQ) whose 'type' attribute
is set to a value of "error" (such a stanza is called an "error is set to a value of "error" (such a stanza is called an "error
stanza" herein). stanza" herein).
o The entity that generates an error stanza SHOULD (but is NOT o The entity that generates an error stanza SHOULD include the
REQUIRED to) include the original XML sent so that the sender can original XML sent so that the sender can inspect and if necessary
inspect and if necessary correct the XML before attempting to correct the XML before attempting to resend.
resend.
o An error stanza MUST contain an <error/> child element. o An error stanza MUST contain an <error/> child element.
o An <error/> child MUST NOT be included if the 'type' attribute has o An <error/> child MUST NOT be included if the 'type' attribute has
a value other than "error" (or if there is no 'type' attribute). a value other than "error" (or if there is no 'type' attribute).
o An entity that receives an error stanza MUST NOT respond to the o An entity that receives an error stanza MUST NOT respond to the
stanza with a further error stanza; this helps to prevent looping. stanza with a further error stanza; this helps to prevent looping.
9.3.2 Syntax 9.3.2 Syntax
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CDATA of the <gone/> element); the associated error type SHOULD be CDATA of the <gone/> element); the associated error type SHOULD be
"modify". "modify".
o <internal-server-error/> -- the server could not process the o <internal-server-error/> -- the server could not process the
stanza because of a misconfiguration or an otherwise-undefined stanza because of a misconfiguration or an otherwise-undefined
internal server error; the associated error type SHOULD be "wait". internal server error; the associated error type SHOULD be "wait".
o <item-not-found/> -- the addressed JID or item requested cannot be o <item-not-found/> -- the addressed JID or item requested cannot be
found; the associated error type SHOULD be "cancel". found; the associated error type SHOULD be "cancel".
o <jid-malformed/> -- the value of the 'to' attribute in the o <jid-malformed/> -- the sending entity has provided or
sender's stanza does not adhere to the syntax defined in communicated an XMPP address (e.g., a value of the 'to' attribute)
Addressing Scheme (Section 3); the associated error type SHOULD be or aspect thereof (e.g., a resource identifier) that does not
"modify". adhere to the syntax defined in Addressing Scheme (Section 3); the
associated error type SHOULD be "modify".
o <not-acceptable/> -- the recipient or server understands the o <not-acceptable/> -- the recipient or server understands the
request but is refusing to process it because it does not meet request but is refusing to process it because it does not meet
criteria defined by the recipient or server (e.g., a local policy criteria defined by the recipient or server (e.g., a local policy
regarding acceptable words in messages); the associated error type regarding acceptable words in messages); the associated error type
SHOULD be "modify". SHOULD be "modify".
o <not-allowed/> -- the recipient or server does not allow any o <not-allowed/> -- the recipient or server does not allow any
entity to perform the action; the associated error type SHOULD be entity to perform the action; the associated error type SHOULD be
"cancel". "cancel".
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namespace MUST be prefixed. An implementation SHOULD generate only namespace MUST be prefixed. An implementation SHOULD generate only
the 'db:' prefix for such elements and MAY accept only the 'db:' the 'db:' prefix for such elements and MAY accept only the 'db:'
prefix. prefix.
11.3 Validation 11.3 Validation
Except as noted with regard to 'to' and 'from' addresses for stanzas Except as noted with regard to 'to' and 'from' addresses for stanzas
within the 'jabber:server' namespace, a server is not responsible for within the 'jabber:server' namespace, a server is not responsible for
validating the XML elements forwarded to a client or another server; validating the XML elements forwarded to a client or another server;
an implementation MAY choose to provide only validated data elements an implementation MAY choose to provide only validated data elements
but is NOT REQUIRED to do so (although an implementation MUST NOT but this is OPTIONAL (although an implementation MUST NOT accept XML
accept XML that is not well-formed). Clients SHOULD NOT rely on the that is not well-formed). Clients SHOULD NOT rely on the ability to
ability to send data which does not conform to the schemas, and send data which does not conform to the schemas, and SHOULD ignore
SHOULD ignore any non-conformant elements or attributes on the any non-conformant elements or attributes on the incoming XML stream.
incoming XML stream. Validation of XML streams and stanzas is NOT Validation of XML streams and stanzas is OPTIONAL, and schemas are
REQUIRED or recommended, and schemas are included herein for included herein for descriptive purposes only.
descriptive purposes only.
11.4 Inclusion of Text Declaration 11.4 Inclusion of Text Declaration
Implementations SHOULD send a text declaration before sending a Implementations SHOULD send a text declaration before sending a
stream header. Applications MUST follow the rules in [XML] regarding stream header. Applications MUST follow the rules in [XML] regarding
the circumstances under which a text declaration is included. the circumstances under which a text declaration is included.
11.5 Character Encoding 11.5 Character Encoding
Implementations MUST support the UTF-8 (RFC 3269 [UTF-8]) Implementations MUST support the UTF-8 (RFC 3269 [UTF-8])
skipping to change at page 1, line 3043 skipping to change at page 65, line 35
for confidentiality: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA for confidentiality: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA
cipher) cipher)
for both: TLS plus SASL EXTERNAL(using the for both: TLS plus SASL EXTERNAL(using the
TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side
certificates) certificates)
14.8 Firewalls 14.8 Firewalls
Communications using XMPP normally occur over [TCP] sockets on port Communications using XMPP normally occur over [TCP] connections on
5222 (client-to-server) or port 5269 (server-to-server), as port 5222 (client-to-server) or port 5269 (server-to-server), as
registered with the IANA (see IANA Considerations (Section 15)). Use registered with the IANA (see IANA Considerations (Section 15)). Use
of these well-known ports allows administrators to easily enable or of these well-known ports allows administrators to easily enable or
disable XMPP activity through existing and commonly-deployed disable XMPP activity through existing and commonly-deployed
firewalls. firewalls.
14.9 Use of base64 in SASL 14.9 Use of base64 in SASL
Both the client and the server MUST verify any [BASE64] data received Both the client and the server MUST verify any [BASE64] data received
during SASL negotiation. An implementation MUST reject (not ignore) during SASL negotiation. An implementation MUST reject (not ignore)
any characters that are not explicitly allowed by the base64 any characters that are not explicitly allowed by the base64
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defined under SASL Definition (Section 6.3). defined under SASL Definition (Section 6.3).
15.9 Port Numbers 15.9 Port Numbers
The IANA currently registers "jabber-client" and "jabber-server" as The IANA currently registers "jabber-client" and "jabber-server" as
keywords for [TCP] ports 5222 and 5269 respectively. The IANA shall keywords for [TCP] ports 5222 and 5269 respectively. The IANA shall
change these registrations to "xmpp-client" and "xmpp-server" change these registrations to "xmpp-client" and "xmpp-server"
respectively. respectively.
These ports SHOULD be used for client-to-server and server-to-server These ports SHOULD be used for client-to-server and server-to-server
communications respectively, but their use is NOT REQUIRED. communications respectively, but their use is OPTIONAL.
Normative References Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003. Encodings", RFC 3548, July 2003.
[CHARSET] Alvestrand, H., "IETF Policy on Character Sets and [CHARSET] Alvestrand, H., "IETF Policy on Character Sets and
skipping to change at page 1, line 3350 skipping to change at page 72, line 15
[IMAP] Crispin, M., "Internet Message Access Protocol - Version [IMAP] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 2060, December 1996. 4rev1", RFC 2060, December 1996.
[JSF] Jabber Software Foundation, "Jabber Software Foundation", [JSF] Jabber Software Foundation, "Jabber Software Foundation",
<http://www.jabber.org/>. <http://www.jabber.org/>.
[POP3] Myers, J. and M. Rose, "Post Office Protocol - Version 3", [POP3] Myers, J. and M. Rose, "Post Office Protocol - Version 3",
STD 53, RFC 1939, May 1996. STD 53, RFC 1939, May 1996.
[RANDOM] Eastlake, D., Crocker, S. and J. Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
[URI] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform [URI] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998. August 1998.
[USINGTLS] [USINGTLS]
Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC
2595, June 1999. 2595, June 1999.
[XML-REG] Mealling, M., "The IETF XML Registry", [XML-REG] Mealling, M., "The IETF XML Registry",
draft-mealling-iana-xmlns-registry-05 (work in progress), draft-mealling-iana-xmlns-registry-05 (work in progress),
June 2003. June 2003.
[XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence [XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", Protocol (XMPP): Instant Messaging and Presence",
draft-ietf-xmpp-im-19 (work in progress), November 2003. draft-ietf-xmpp-im-21 (work in progress), January 2004.
Author's Address Author's Address
Peter Saint-Andre Peter Saint-Andre
Jabber Software Foundation Jabber Software Foundation
EMail: stpeter@jabber.org EMail: stpeter@jabber.org
Appendix A. Nodeprep Appendix A. Nodeprep
skipping to change at page 1, line 3987 skipping to change at page 85, line 49
headers. XMPP specifies inclusion of that attribute, with a value of headers. XMPP specifies inclusion of that attribute, with a value of
'1.0', as a way to signal support for the stream features '1.0', as a way to signal support for the stream features
(authentication, encryption, etc.) defined under Version Support (authentication, encryption, etc.) defined under Version Support
(Section 4.2.1) herein. (Section 4.2.1) herein.
Appendix E. Revision History Appendix E. Revision History
Note to RFC Editor: please remove this entire appendix, and the Note to RFC Editor: please remove this entire appendix, and the
corresponding entries in the table of contents, prior to publication. corresponding entries in the table of contents, prior to publication.
E.1 Changes from draft-ietf-xmpp-core-20 E.1 Changes from draft-ietf-xmpp-core-21
o Clarified "<major>.<minor>" version numbering and basis for
comparison.
o Clarified relationship between certificate names and JIDs.
o Clarified relationship between SASL usernames and JIDs.
o Changed "TCP socket" to "TCP connection".
o Added informative reference to RFC 1750 with regard to randomness
of stream IDs.
o Changed "Server informs ... to proceed" to "Server informs ...
that it is allowed to proceed".
o Replaced "NOT REQUIRED" with appropriate conformance terminology.
E.2 Changes from draft-ietf-xmpp-core-20
o Completed changes necessary to address IESG feedback. o Completed changes necessary to address IESG feedback.
E.2 Changes from draft-ietf-xmpp-core-19 E.3 Changes from draft-ietf-xmpp-core-19
o Fixed several typographical errors. o Fixed several typographical errors.
o Restricted values of 'type' attribute for IQ stanzas to those o Restricted values of 'type' attribute for IQ stanzas to those
defined in the schema (i.e., changed SHOULD to MUST) to ensure defined in the schema (i.e., changed SHOULD to MUST) to ensure
consistency with text in XMPP IM. consistency with text in XMPP IM.
o Added reference to RFC 3548. o Added reference to RFC 3548.
o Added the <not-authorized/> stanza error. o Added the <not-authorized/> stanza error.
skipping to change at page 1, line 4020 skipping to change at page 87, line 8
o Clarified several sentences in the dialback narrative. o Clarified several sentences in the dialback narrative.
o Clarified use of stringprep profiles and added reference to RFC o Clarified use of stringprep profiles and added reference to RFC
3490. 3490.
o Added security consideration regarding lack of SASL channel o Added security consideration regarding lack of SASL channel
binding to TLS per discussion at IETF 58 meeting. binding to TLS per discussion at IETF 58 meeting.
o Adjusted formatting to conform to RFC Editor requirements. o Adjusted formatting to conform to RFC Editor requirements.
E.3 Changes from draft-ietf-xmpp-core-18 E.4 Changes from draft-ietf-xmpp-core-18
o Added the 'xml:lang' attribute to the root <stream/> element per o Added the 'xml:lang' attribute to the root <stream/> element per
previous consensus and list discussion. previous consensus and list discussion.
o Changed "jabber-server" and "jabber-client" service names to o Changed "jabber-server" and "jabber-client" service names to
"xmpp-server" and "xmpp-client". "xmpp-server" and "xmpp-client".
o Added the <gone/>, <not-acceptable/>, and <redirect/> stanza o Added the <gone/>, <not-acceptable/>, and <redirect/> stanza
errors. errors.
skipping to change at page 1, line 4073 skipping to change at page 88, line 15
o Added section on resource binding to compensate for changes to o Added section on resource binding to compensate for changes to
SASL authorization identity text. SASL authorization identity text.
o Specified ABNF for JIDs. o Specified ABNF for JIDs.
o Checked all references. o Checked all references.
o Completed a thorough proofreading and consistency check of the o Completed a thorough proofreading and consistency check of the
entire text. entire text.
E.4 Changes from draft-ietf-xmpp-core-17 E.5 Changes from draft-ietf-xmpp-core-17
o Specified that UTF-8 is the only allowable encoding. o Specified that UTF-8 is the only allowable encoding.
o Added stream errors for <bad-namespace-prefix/>, <invalid-xml/>, o Added stream errors for <bad-namespace-prefix/>, <invalid-xml/>,
and <restricted-xml/>, as well as a <bad-format/> error for and <restricted-xml/>, as well as a <bad-format/> error for
generic XML error conditions. generic XML error conditions.
o Folded Nodeprep and Resourceprep profiles into this document. o Folded Nodeprep and Resourceprep profiles into this document.
o Moved most delivery handling rules from XMPP IM to XMPP Core. o Moved most delivery handling rules from XMPP IM to XMPP Core.
o Moved detailed stanza syntax descriptions from XMPP Core to XMPP o Moved detailed stanza syntax descriptions from XMPP Core to XMPP
IM. IM.
o Moved stanza schemas from XMPP Core to XMPP IM. o Moved stanza schemas from XMPP Core to XMPP IM.
E.5 Changes from draft-ietf-xmpp-core-16 E.6 Changes from draft-ietf-xmpp-core-16
o Added <conflict/> and <unsupported-encoding/> stream errors. o Added <conflict/> and <unsupported-encoding/> stream errors.
o Changed the datatype for the <see-other-host/> and o Changed the datatype for the <see-other-host/> and
<unsupported-version/> stream errors from 'xs:string' to 'empty'. <unsupported-version/> stream errors from 'xs:string' to 'empty'.
o Further clarified server handling of the basic stanza kinds. o Further clarified server handling of the basic stanza kinds.
o Further clarified character encoding rules per list discussion. o Further clarified character encoding rules per list discussion.
skipping to change at page 1, line 4112 skipping to change at page 89, line 8
o Added stream closure to SASL failure cases in order to mirror o Added stream closure to SASL failure cases in order to mirror
handling of TLS failures. handling of TLS failures.
o Added section on compliance requirements for server and client o Added section on compliance requirements for server and client
implementations. implementations.
o Added non-normative section on differences between Jabber usage o Added non-normative section on differences between Jabber usage
and XMPP specifications. and XMPP specifications.
E.6 Changes from draft-ietf-xmpp-core-15 E.7 Changes from draft-ietf-xmpp-core-15
o Added <connection-timeout/> and <policy-violation/> stream errors. o Added <connection-timeout/> and <policy-violation/> stream errors.
o Added <aborted/> SASL error and clarified <bad-protocol/> error. o Added <aborted/> SASL error and clarified <bad-protocol/> error.
o Made 'id' required for IQ stanzas. o Made 'id' required for IQ stanzas.
E.7 Changes from draft-ietf-xmpp-core-14 E.8 Changes from draft-ietf-xmpp-core-14
o Added SRV lookup for client-to-server communications. o Added SRV lookup for client-to-server communications.
o Changed server SRV record to conform to RFC 2782; specifically, o Changed server SRV record to conform to RFC 2782; specifically,
the service identifier was changed from 'jabber' to the service identifier was changed from 'jabber' to
'jabber-server'. 'jabber-server'.
E.8 Changes from draft-ietf-xmpp-core-13 E.9 Changes from draft-ietf-xmpp-core-13
o Clarified stream restart after successful TLS and SASL o Clarified stream restart after successful TLS and SASL
negotiation. negotiation.
o Clarified requirement for resolution of DNS hostnames. o Clarified requirement for resolution of DNS hostnames.
o Clarified text regarding namespaces. o Clarified text regarding namespaces.
o Clarified examples regarding empty <stream:features/> element. o Clarified examples regarding empty <stream:features/> element.
o Added several more SASL error conditions. o Added several more SASL error conditions.
o Changed <invalid-xml/> stream error to <improper-addressing/> and o Changed <invalid-xml/> stream error to <improper-addressing/> and
added to schema. added to schema.
o Made small editorial changes and fixed several schema errors. o Made small editorial changes and fixed several schema errors.
E.9 Changes from draft-ietf-xmpp-core-12 E.10 Changes from draft-ietf-xmpp-core-12
o Moved server dialback to a separate section; clarified its o Moved server dialback to a separate section; clarified its
security characteristics and its role in the protocol. security characteristics and its role in the protocol.
o Adjusted error handling syntax and semantics per list discussion. o Adjusted error handling syntax and semantics per list discussion.
o Further clarified length of node identifiers and total length of o Further clarified length of node identifiers and total length of
JIDs. JIDs.
o Documented message type='normal'. o Documented message type='normal'.
o Corrected several small errors in the TLS and SASL sections. o Corrected several small errors in the TLS and SASL sections.
o Corrected several errors in the schemas. o Corrected several errors in the schemas.
E.10 Changes from draft-ietf-xmpp-core-11 E.11 Changes from draft-ietf-xmpp-core-11
o Corrected several small errors in the TLS and SASL sections. o Corrected several small errors in the TLS and SASL sections.
o Made small editorial changes and fixed several schema errors. o Made small editorial changes and fixed several schema errors.
E.11 Changes from draft-ietf-xmpp-core-10 E.12 Changes from draft-ietf-xmpp-core-10
o Adjusted TLS content regarding certificate validation process. o Adjusted TLS content regarding certificate validation process.
o Specified that stanza error extensions for specific applications o Specified that stanza error extensions for specific applications
are to be properly namespaced children of the relevant descriptive are to be properly namespaced children of the relevant descriptive
element. element.
o Clarified rules for inclusion of the 'id' attribute. o Clarified rules for inclusion of the 'id' attribute.
o Specified that the 'xml:lang' attribute SHOULD be included (per o Specified that the 'xml:lang' attribute SHOULD be included (per
list discussion). list discussion).
o Made small editorial changes and fixed several schema errors. o Made small editorial changes and fixed several schema errors.
E.12 Changes from draft-ietf-xmpp-core-09 E.13 Changes from draft-ietf-xmpp-core-09
o Fixed several dialback error conditions. o Fixed several dialback error conditions.
o Cleaned up rules regarding TLS and certificate processing based on o Cleaned up rules regarding TLS and certificate processing based on
off-list feedback. off-list feedback.
o Changed <stream-condition/> and <stanza-condition/> elements to o Changed <stream-condition/> and <stanza-condition/> elements to
<condition/>. <condition/>.
o Added or modified several stream and stanza error conditions. o Added or modified several stream and stanza error conditions.
o Specified only one child allowed for IQ, or two if type="error". o Specified only one child allowed for IQ, or two if type="error".
o Fixed several errors in the schemas. o Fixed several errors in the schemas.
E.13 Changes from draft-ietf-xmpp-core-08 E.14 Changes from draft-ietf-xmpp-core-08
o Incorporated list discussion regarding addressing, SASL, TLS, TCP, o Incorporated list discussion regarding addressing, SASL, TLS, TCP,
dialback, namespaces, extensibility, and the meaning of 'ignore' dialback, namespaces, extensibility, and the meaning of 'ignore'
for routers and recipients. for routers and recipients.
o Specified dialback error conditions. o Specified dialback error conditions.
o Made small editorial changes to address RFC Editor requirements. o Made small editorial changes to address RFC Editor requirements.
E.14 Changes from draft-ietf-xmpp-core-07 E.15 Changes from draft-ietf-xmpp-core-07
o Made several small editorial changes. o Made several small editorial changes.
E.15 Changes from draft-ietf-xmpp-core-06 E.16 Changes from draft-ietf-xmpp-core-06
o Added text regarding certificate validation in TLS negotiation per o Added text regarding certificate validation in TLS negotiation per
list discussion. list discussion.
o Clarified nature of XML restrictions per discussion with W3C, and o Clarified nature of XML restrictions per discussion with W3C, and
moved XML Restrictions subsection under "XML Usage within XMPP". moved XML Restrictions subsection under "XML Usage within XMPP".
o Further clarified that XML streams are unidirectional. o Further clarified that XML streams are unidirectional.
o Changed stream error and stanza error namespace names to conform o Changed stream error and stanza error namespace names to conform
to the format defined in The IETF XML Registry. to the format defined in The IETF XML Registry.
o Removed note to RFC Editor regarding provisional namespace names. o Removed note to RFC Editor regarding provisional namespace names.
E.16 Changes from draft-ietf-xmpp-core-05 E.17 Changes from draft-ietf-xmpp-core-05
o Added <invalid-namespace/> as a stream error condition. o Added <invalid-namespace/> as a stream error condition.
o Adjusted security considerations per discussion at IETF 56 and on o Adjusted security considerations per discussion at IETF 56 and on
list. list.
E.17 Changes from draft-ietf-xmpp-core-04 E.18 Changes from draft-ietf-xmpp-core-04
o Added server-to-server examples for TLS and SASL. o Added server-to-server examples for TLS and SASL.
o Changed error syntax, rules, and examples based on list o Changed error syntax, rules, and examples based on list
discussion. discussion.
o Added schemas for the TLS, stream error, and stanza error o Added schemas for the TLS, stream error, and stanza error
namespaces. namespaces.
o Added note to RFC Editor regarding provisional namespace names. o Added note to RFC Editor regarding provisional namespace names.
o Made numerous small editorial changes and clarified text o Made numerous small editorial changes and clarified text
throughout. throughout.
E.18 Changes from draft-ietf-xmpp-core-03 E.19 Changes from draft-ietf-xmpp-core-03
o Clarified rules and procedures for TLS and SASL. o Clarified rules and procedures for TLS and SASL.
o Amplified stream error code syntax per list discussion. o Amplified stream error code syntax per list discussion.
o Made numerous small editorial changes. o Made numerous small editorial changes.
E.19 Changes from draft-ietf-xmpp-core-02 E.20 Changes from draft-ietf-xmpp-core-02
o Added dialback schema. o Added dialback schema.
o Removed all DTDs since schemas provide more complete definitions. o Removed all DTDs since schemas provide more complete definitions.
o Added stream error codes. o Added stream error codes.
o Clarified error code "philosophy". o Clarified error code "philosophy".
E.20 Changes from draft-ietf-xmpp-core-01 E.21 Changes from draft-ietf-xmpp-core-01
o Updated the addressing restrictions per list discussion and added o Updated the addressing restrictions per list discussion and added
references to the new Nodeprep and Resourceprep profiles. references to the new Nodeprep and Resourceprep profiles.
o Corrected error in Use of SASL regarding 'version' attribute. o Corrected error in Use of SASL regarding 'version' attribute.
o Made numerous small editorial changes. o Made numerous small editorial changes.
E.21 Changes from draft-ietf-xmpp-core-00 E.22 Changes from draft-ietf-xmpp-core-00
o Added information about TLS from list discussion. o Added information about TLS from list discussion.
o Clarified meaning of "ignore" based on list discussion. o Clarified meaning of "ignore" based on list discussion.
o Clarified information about Universal Character Set data and o Clarified information about Universal Character Set data and
character encodings. character encodings.
o Provided base64-decoded information for examples. o Provided base64-decoded information for examples.
o Fixed several errors in the schemas. o Fixed several errors in the schemas.
o Made numerous small editorial fixes. o Made numerous small editorial fixes.
E.22 Changes from draft-miller-xmpp-core-02 E.23 Changes from draft-miller-xmpp-core-02
o Brought Use of SASL section into line with discussion on list and o Brought Use of SASL section into line with discussion on list and
at IETF 55 meeting. at IETF 55 meeting.
o Added information about the optional 'xml:lang' attribute per o Added information about the optional 'xml:lang' attribute per
discussion on list and at IETF 55 meeting. discussion on list and at IETF 55 meeting.
o Specified that validation is neither required nor recommended, and o Specified that validation is neither required nor recommended, and
that the formal definitions (DTDs and schemas) are included for that the formal definitions (DTDs and schemas) are included for
descriptive purposes only. descriptive purposes only.
skipping to change at page 1, line 4395 skipping to change at line 4424
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
XMPP Working Group P. Saint-Andre (ed.)
Internet-Draft Jabber Software Foundation
Expires: July 6, 2004 January 6, 2004
Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
and Presence
draft-ietf-xmpp-im-20
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on July 6, 2004.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This memo describes extensions to and applications of the core
features of the Extensible Messaging and Presence Protocol (XMPP)
that provide the basic instant messaging (IM) and presence
functionality defined in RFC 2779.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Syntax of XML Stanzas . . . . . . . . . . . . . . . . . . . 4
3. Session Establishment . . . . . . . . . . . . . . . . . . . 11
4. Exchanging Messages . . . . . . . . . . . . . . . . . . . . 14
5. Exchanging Presence Information . . . . . . . . . . . . . . 16
6. Managing Subscriptions . . . . . . . . . . . . . . . . . . . 25
7. Roster Management . . . . . . . . . . . . . . . . . . . . . 26
8. Integration of Roster Items and Presence Subscriptions . . . 31
9. Subscription States . . . . . . . . . . . . . . . . . . . . 54
10. Blocking Communication . . . . . . . . . . . . . . . . . . . 59
11. Server Rules for Handling XML Stanzas . . . . . . . . . . . 79
12. IM and Presence Compliance Requirements . . . . . . . . . . 81
13. Internationalization Considerations . . . . . . . . . . . . 82
14. Security Considerations . . . . . . . . . . . . . . . . . . 82
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 83
Normative References . . . . . . . . . . . . . . . . . . . . 84
Informative References . . . . . . . . . . . . . . . . . . . 85
Author's Address . . . . . . . . . . . . . . . . . . . . . . 85
A. vCards . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
B. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 86
C. Differences Between Jabber IM/Presence and XMPP . . . . . . 98
D. Revision History . . . . . . . . . . . . . . . . . . . . . . 99
Intellectual Property and Copyright Statements . . . . . . . 106
1. Introduction
1.1 Overview
The Extensible Messaging and Presence Protocol (XMPP) is a protocol
for streaming XML [XML] elements in order to exchange messages and
presence information in close to real time. The core features of
XMPP are defined in Extensible Messaging and Presence Protocol
(XMPP): Core [XMPP-CORE]. These features -- mainly XML streams, use
of TLS and SASL, and the <message/>, <presence/>, and <iq/> 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 [XML-NAMES]. This memo describes extensions to and
applications of the core features of XMPP that provide the basic
functionality expected of an instant messaging (IM) and presence
application as defined in RFC 2779 [IMP-REQS].
1.2 Requirements
For the purposes of this memo, the requirements of a basic instant
messaging and presence application are defined by [IMP-REQS], which
at a high level 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
[IMP-REQS], and the interested reader is directed to that document
regarding the requirements addressed herein.
[IMP-REQS] also stipulates that presence services must be separable
from instant messaging services; i.e., it must be possible to use the
protocol to provide a presence service, an instant messaging service,
or both. Although the text of this memo assumes that implementations
and deployments will want to offer a unified instant messaging and
presence service, there is no requirement that a service must offer
both a presence service and an instant messaging service, and the
protocol makes it possible to offer separate and distinct services
for presence and for instant messaging.
Note: While XMPP-based instant messaging and presence meets the
requirements of [IMP-REQS], it was not designed explicitly with that
specification 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 memo
because they are not required by [IMP-REQS].
1.3 Terminology
This memo inherits the terminology defined in [XMPP-CORE].
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 [TERMS].
1.4 Contributors
Most of the core aspects of the Extensible Messaging and Presence
Protocol were developed originally within the Jabber open-source
community in 1999. This community was founded by Jeremie Miller, who
released source code for the initial version of the jabberd server in
January 1999. Major early contributors to the base protocol also
included Ryan Eatmon, Peter Millard, Thomas Muldowney, and Dave
Smith. Work specific to instant messaging and presence by the XMPP
Working Group has concentrated especially on IM session establishment
and communication blocking (privacy rules); the session establishment
protocol was mainly developed by Rob Norris and Joe Hildebrand, and
the privacy rules protocol was originally contributed by Peter
Millard.
1.5 Acknowledgements
Thanks are due to a number of individuals in addition to the
contributors listed. Although it is difficult to provide a complete
list, the following individuals were particularly helpful in defining
the protocols or in commenting on the specifications in this memo:
Thomas Charron, Richard Dobson, Schuyler Heath, Jonathan Hogg, Craig
Kaes, Jacek Konieczny, Alexey Melnikov, Keith Minkler, Julian Missig,
Pete Resnick, Marshall Rose, Alexey Shchepin, Jean-Louis Seguineau,
Iain Shigeoka, and David Waite. Thanks also to members of the XMPP
Working Group and the IETF community for comments and feedback
provided throughout the life of this memo.
2. Syntax of XML Stanzas
The basic semantics and common attributes of XML stanzas qualified by
the 'jabber:client' and 'jabber:server' namespaces are defined in
[XMPP-CORE]. However, these namespaces also define various child
elements, as well as values for the common 'type' attribute, that are
specific to instant messaging and presence applications. Thus,
before addressing particular "use cases" for such applications, we
here further describe the syntax of XML stanzas, thereby
supplementing the discussion in [XMPP-CORE].
2.1 Message Syntax
Message stanzas in the 'jabber:client' or 'jabber:server' namespace
are used to "push" information to another entity. Common uses in
instant messaging applications include single messages, messages sent
in the context of a chat conversation, messages sent in the context
of a multi-user chat room, headlines, and errors.
2.1.1 Types of Message
The 'type' attribute of a message stanza is RECOMMENDED; if included,
it specifies the conversational context of the message, thus
providing a hint regarding presentation (e.g., in a GUI). If
included, the 'type' attribute MUST have one of the following values:
o chat -- The message is sent in the context of a one-to-one chat
conversation. A compliant client SHOULD present the message 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, refer to
[XMPP-CORE]). A compliant client SHOULD present an appropriate
interface informing the sender of the nature of the error.
o groupchat -- The message is sent in the context of a multi-user
chat environment. A compliant client SHOULD present the message
an interface enabling many-to-many chat between the parties,
including a roster of parties in the chatroom and an appropriate
conversation history. Full definition of XMPP-based groupchat
protocols is out of scope for this memo.
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 the message 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 single message that is sent outside the
context of a one-to-one conversation or groupchat, and to which it
is expected that the recipient will reply. A compliant client
SHOULD present the message in an interface enabling the recipient
to reply.
An IM application SHOULD support all of the foregoing message types;
if an application receives a message with no 'type' attribute or the
application does not understand the value of the 'type' attribute
provided, it MUST consider the message to be of type "normal" (i.e.,
"normal" is the default). The "error" type MUST be generated only in
response to an error related to a message received from another
entity.
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').
2.1.2 Child Elements
As described under extended namespaces (Section 2.4), a message
stanza MAY contain any properly-namespaced child element.
In accordance with the default namespace declaration, by default a
message stanza is in the 'jabber:client' or 'jabber:server'
namespace, which defines certain allowable children of message
stanzas. If the message stanza is of type "error", it MUST include
an <error/> child; for details, see [XMPP-CORE]. Otherwise, the
message stanza MAY contain any of the following child elements
without an explicit namespace declaration:
1. <subject/>
2. <body/>
3. <thread/>
2.1.2.1 Subject
The <subject/> element contains XML character data that specifies the
topic of the message. The <subject/> element MUST NOT possess any
attributes, with the exception of the 'xml:lang' attribute. Multiple
instances of the <subject/> element MAY be included for the purpose
of providing alternate versions of the same subject, but only if each
instance possesses an 'xml:lang' attribute with a distinct language
value. The <subject/> element MUST NOT contain mixed content (as
defined in Section 3.2.2 of [XML]).
2.1.2.2 Body
The <body/> element contains XML character data that specifies the
textual contents of the message; this child element is normally
included but NOT REQUIRED. The <body/> element MUST NOT possess any
attributes, with the exception of the 'xml:lang' attribute. Multiple
instances of the <body/> element MAY be included but only if each
instance possesses an 'xml:lang' attribute with a distinct language
value. The <body/> element MUST NOT contain mixed content (as
defined in Section 3.2.2 of [XML]).
2.1.2.3 Thread
The <thread/> element contains XML character data that specifies an
identifier that is used for tracking a conversation thread (sometimes
referred to as an "instant messaging session") between two entities.
The value of the <thread/> element is generated by the sender and
that SHOULD be copied back in any replies. If used, it MUST be
unique to that conversation thread within the stream and MUST be
consistent throughout that conversation (a client that receives a
message from the same full JID but with a different thread ID MUST
assume that the message in question exists outside the context of the
existing conversation thread). The use of the <thread/> element is
OPTIONAL and is not used to identify individual messages, only
conversations. A message stanza MUST NOT contain more than one
<thread/> element. The <thread/> element MUST NOT possess any
attributes. The value of the <thread/> element MUST be treated as
opaque by entities; no semantic meaning may be derived from it, and
only exact comparisons may be made against it. The <thread/> element
MUST NOT contain mixed content (as defined in Section 3.2.2 of
[XML]).
2.2 Presence Syntax
Presence stanzas are used in the 'jabber:client' or 'jabber:server'
namespace to express an entity's current availability status (offline
or online, along with various sub-states of the latter and optional
user-defined descriptive text), and to communicate that status to
other entities. Presence stanzas are also used to negotiate and
manage subscriptions to the presence of other entities.
2.2.1 Types of Presence
The 'type' attribute of a presence stanza is OPTIONAL. A presence
stanza that does not possess a 'type' attribute is used to signal to
the server that the sender is online and available for communication.
If included, the 'type' attribute specifies a lack of availability, a
request to manage a subscription to another entity's presence, a
request for another entity's current presence, or an error related to
a previously-sent presence stanza. If included, the 'type' attribute
MUST have one of the following values:
o unavailable -- Signals that the entity is no longer available for
communication.
o subscribe -- The sender wishes to subscribe to the recipient's
presence.
o subscribed -- The sender has allowed the recipient to receive
their presence.
o unsubscribe -- A notification that an entity is unsubscribing from
another entity's presence.
o unsubscribed -- The subscription request has been denied or a
previously-granted subscription has been cancelled.
o probe -- A request for an entity's current presence; SHOULD be
generated only by a server and SHOULD NOT be generated by a
client.
o error -- An error has occurred regarding processing or delivery of
a previously-sent presence stanza.
For detailed information regarding presence semantics and the
subscription model used in the context of XMPP-based instant
messaging and presence applications, refer to Exchanging Presence
Information (Section 5) and Managing Subscriptions (Section 6).
2.2.2 Child Elements
As described under extended namespaces (Section 2.4), a presence
stanza MAY contain any properly-namespaced child element.
In accordance with the default namespace declaration, by default a
presence stanza is in the 'jabber:client' or 'jabber:server'
namespace, which defines certain allowable children of presence
stanzas. If the presence stanza is of type "error", it MUST include
an <error/> child; for details, see [XMPP-CORE]. If the presence
stanza possesses no 'type' attribute, it MAY contain any of the
following child elements (note that the <status/> child MAY be sent
in a presence stanza of type "unavailable" or, for historical
reasons, "subscribe"):
1. <show/>
2. <status/>
3. <priority/>
2.2.2.1 Show
The OPTIONAL <show/> element contains XML character data that
specifies the particular availability status of an entity or specific
resource. A presence stanza MUST NOT contain more than one <show/>
element. The <show/> element MUST NOT possess any attributes. The
XML character data contained in the <show/> element is not intended
to be human-readable. If provided, the CDATA value MUST be one of
the following (additional availability types could be defined through
a properly-namespaced child element of the presence stanza):
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").
If no <show/> element is provided, the entity is assumed to be online
and available.
2.2.2.2 Status
The OPTIONAL <status/> element contains a natural-language
description of availability status. It is normally used in
conjunction with the show element to provide a detailed description
of an availability state (e.g., "In a meeting"). The <status/>
element MUST NOT possess any attributes, with the exception of the
'xml:lang' attribute. Multiple instances of the <status/> element
MAY be included but only if each instance possesses an 'xml:lang'
attribute with a distinct language value.
2.2.2.3 Priority
The OPTIONAL <priority/> element contains XML character data that
specifies the priority level of the resource. The value may be any
integer between -128 and +127. A presence stanza MUST NOT contain
more than one <priority/> element. The <priority/> element MUST NOT
possess any attributes. If no priority is provided, a server SHOULD
consider the priority to be zero. For information regarding the
semantics of priority values in stanza routing within instant
messaging and presence applications, refer to Server Rules for
Handling XML Stanzas (Section 11).
2.3 IQ Syntax
IQ stanzas provide a structured request-response mechanism. The
basic semantics of that mechanism are defined in [XMPP-CORE], whereas
the specific semantics required to complete particular use cases are
defined in all cases by an extended namespace (Section 2.4) (note
that the 'jabber:client' and 'jabber:server' namespaces do not define
any children of IQ stanzas). This memo defines two such extended
namespaces, one for Roster Management (Section 7) and the other for
Blocking Communication (Section 10); however, an IQ stanza MAY
contain structured information qualified by any extended namespace.
2.4 Extended Namespaces
While the three XML stanza kinds defined in the "jabber:client" or
"jabber:server" namespace (along with their attributes and child
elements) provide a basic level of functionality for messaging and
presence, XMPP uses XML namespaces to extend the stanzas for the
purpose of providing additional functionality. Thus a message or
presence MAY contain one or more optional child elements containing
content that extends the meaning of the message (e.g., an
XHTML-formatted version of the message body), and an IQ stanza MAY
contain one such child element. This child element MAY have any name
and MUST possess an 'xmlns' namespace declaration (other than
"jabber:client", "jabber:server", or "http://etherx.jabber.org/
streams") that defines all data contained within the child element.
Support for any given extended namespace is OPTIONAL on the part of
any implementation (aside from the extended namespaces defined
herein). If an entity does not understand such a namespace, the
entity's expected behavior depends on whether the entity is (1) the
recipient or (2) an entity that is routing the stanza to the
recipient:
Recipient: If a recipient receives a stanza that contains a child
element it does not understand, it SHOULD ignore that specific XML
data, i.e., it SHOULD not process it or present it to a user or
associated application (if any). In particular:
* If an entity receives a message or presence stanza that
contains XML data qualified by a namespace it does not
understand, the portion of the stanza that is in the unknown
namespace SHOULD be ignored.
* If an entity receives a message stanza whose only child element
is qualified by a namespace it does not understand, it MUST
ignore the entire stanza.
* If an entity receives an IQ stanza of type "get" or "set"
containing a child element qualified by a namespace it does not
understand, the entity SHOULD return an IQ stanza of type
"error" with an error condition of <feature-not-implemented/>.
Router: If a routing entity (usually a server) handles a stanza that
contains a child element it does not understand, it SHOULD ignore
the associated XML data by passing it on untouched to the
recipient.
3. Session Establishment
Most instant messaging and presence applications based on XMPP are
implemented via a client-server architecture that requires a client
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 client can establish
an instant messaging and presence session. These are:
1. Stream Authentication -- a client MUST complete stream
authentication as documented in [XMPP-CORE] before attempting to
establish a session or send any XML stanzas.
2. Resource Binding -- after completing stream authentication, a
client MUST bind a resource to the stream so that the client's
address is of the form <user@domain/resource>, after which the
entity is said to be a "connected resource" in the terminology of
[XMPP-CORE].
If a server supports sessions, it MUST include a <session/> element
qualified by the 'urn:ietf:params:xml:ns:xmpp-session' namespace in
the stream features it advertises to a client after the completion of
stream authentication as defined in [XMPP-CORE]:
Server advertises session establishment feature to client:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
id='c2s_345'
from='example.com'
version='1.0'>
<stream:features>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'>
</stream:features>
Upon being so informed that session establishment is required (and
after completing resource binding), the client MUST establish a
session if it desires to engage in instant messaging and presence
functionality; it completes this step by sending to the server an IQ
stanza of type "set" containing an empty <session/> child element
qualified by the 'urn:ietf:params:xml:ns:xmpp-session' namespace:
Step 1: Client requests session with server:
<iq from='someuser@example.com'
to='example.com'
type='set'
id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
</iq>
Step 2: Server informs client that session has been created:
<iq from='example.com'
to='someuser@example.com'
type='result'
id='sess_1'/>
Upon establishing a session, a connected resource (in the terminology
of [XMPP-CORE]) is said to be an "active resource".
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 resource
associated with a resource identifier of the same name.
If the server encounters an internal condition that prevents it from
creating the session, it MUST return an error.
Step 2 (alt): Server responds with error (internal server error):
<iq type='error' id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
<error type='wait'>
<internal-server-error
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If the username or resource is not allowed to create a session, the
server MUST return an error (e.g., forbidden).
Step 2 (alt): Server responds with error (username or resource not
allowed to create session):
<iq type='error' id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
<error type='auth'>
<forbidden
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If there is already an active resource of the same name, the server
MUST either (1) terminate the active resource and allow the
newly-requested session, or (2) disallow the newly-requested session
and maintain the active resource. Which of these the server does is
up to the implementation, although it is RECOMMENDED to implement
case #1. In case #1, the server SHOULD send a <conflict/> stream
error to the active resource, terminate the XML stream and underlying
TCP connection for the active resource, and return a IQ stanza of
type "result" (indicating success) to the newly-requested session. In
case #2, the server SHOULD send a <conflict/> stanza error to the
newly-requested session but maintain the XML stream for that
connection so that the newly-requested session has an opportunity to
negotiate a non-conflicting resource identifier before sending
another request for session establishment.
Step 2 (alt): Server informs active resource of resource conflict
(case #1):
<stream:error>
<conflict xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
</stream:error>
</stream:stream>
Step 2 (alt): Server informs newly-requested session of resource
conflict (case #2):
<iq type='error' id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
<error type='cancel'>
<conflict xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
After establishing a session, a client SHOULD send initial presence
and request its roster as described below, although these actions are
NOT REQUIRED.
Note: Before allowing the creation of instant messaging and presence
sessions, a server MAY require prior account provisioning. Possible
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 [JSF] at <http://www.jabber.org/
protocol/> but is out of scope for this memo.
4. Exchanging Messages
Exchanging messages is a basic use of XMPP and is brought about when
a user generates a message stanza that is addressed to another
entity. As defined under Server Rules for Handling XML Stanzas
(Section 11), 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 Message Syntax
(Section 2.1).
4.1 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 <message/> stanza. If the message is being
sent in reply to a message previously received from an address of the
form <user@domain/resource> (e.g., within the context of a chat
session), the value of the 'to' address SHOULD be the full JID (of
the form <user@domain/resource>) rather than merely of the form
<user@domain> 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
<user@domain> rather than of the form <user@domain/resource>.
4.2 Specifying a Message Type
As noted, it is RECOMMENDED for a message stanza to possess a 'type'
attribute whose value captures the conversational context (if any) of
the message (see Type (Section 2.1.1)).
The following example shows a valid value of the 'type' attribute:
Example: A message of a defined type:
<message
to='romeo@example.net'
from='juliet@example.com/balcony'
type='chat'
xml:lang='en'>
<body>Wherefore art thou, Romeo?</body>
</message>
4.3 Specifying a Message Body
A message stanza MAY (and often will) contain a child <body/> element
whose XML character data specifies the primary meaning of the message
(see Body (Section 2.1.2.2)).
Example: A message with a body:
<message
to='romeo@example.net'
from='juliet@example.com/balcony'
type='chat'
xml:lang='en'>
<body>Wherefore art thou, Romeo?</body>
<body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>
</message>
4.4 Specifying a Message Subject
A message stanza MAY contain one or more child <subject/> elements
specifying the topic of the message (see Subject (Section 2.1.2.1)).
Example: A message with a subject:
<message
to='romeo@example.net'
from='juliet@example.com/balcony'
type='chat'
xml:lang='en'>
<subject>I implore you!</subject>
<subject
xml:lang='cz'>&#x00DA;p&#x011B;nliv&#x011B; prosim!</subject>
<body>Wherefore art thou, Romeo?</body>
<body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>
</message>
4.5 Specifying a Conversation Thread
A message stanza MAY contain a child <thread/> element specifying the
conversation thread in which the message is situated, for the purpose
of tracking the conversation (see Thread (Section 2.1.2.3)).
Example: A threaded conversation:
<message
to='romeo@example.net/orchard'
from='juliet@example.com/balcony'
type='chat'>
<body>Art thou not Romeo, and a Montague?</body>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
<message
to='juliet@example.com/balcony'
from='romeo@example.net/orchard'
type='chat'>
<body>Neither, fair saint, if either thee dislike.</body>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
<message
to='romeo@example.net/orchard'
from='juliet@example.com/balcony'
type='chat'>
<body>How cam'st thou hither, tell me, and wherefore?</body>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
5. 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 (in the terminology
of RFC 2778 [IMP-MODEL], we can say that the only watchers in XMPP
are subscribers). (Note: While presence information MAY be provided
on a user's behalf by an automated service, normally it is provided
by the user's client.)
For information regarding the syntax of presence stanzas as well as
their defined attributes and child elements, refer to [XMPP-CORE].
5.1 Client and Server Presence Responsibilities
After establishing a session, a client 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 client) and (2)
MUST possess no 'type' attribute (signalling the user's
availability). After sending initial presence, an active resource is
said to be an "available resource".
Upon receiving initial presence from a client, the user's server MUST
do the following if there is not already one or more available
resources for the user (if there is already one or more available
resources for the user, the server obviously does not need to send
the presence probes, since it already possesses the requisite
information):
1. Send presence probes (i.e., presence stanzas whose 'type'
attribute is set to a value of "probe") from the full JID (e.g.,
<user@example.com/resource>) of the user to the bare JID (e.g.,
<contact@example.org>) 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".
2. Broadcast initial presence from the full JID (e.g.,
<user@example.com/resource>) of the user to the bare JID (e.g.,
<contact@example.org>) 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".
In addition, the user's server MUST broadcast initial presence from
the user's new available resource to any of the user's existing
available resources (if any).
Upon receiving a presence probe from the user, the contact's server
SHOULD reply as follows:
1. If the user is not in the contact's roster with a subscription
state of "From", "From + Pending Out", or "Both" (as defined
under Subscription States (Section 9)), the contact's server MUST
return a presence stanza of type "error" in response to the
presence probe (however, if a 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). Specifically:
* if the user is in the contact's roster with a subscription
state of "None", "None + Pending Out", or "To", the contact's
server MUST return a <forbidden/> stanza error in response to
the presence probe.
* if the user is in the contact's roster with a subscription
state of "None + Pending In", "None + Pending Out/In", or "To
+ Pending In", the contact's server MUST return a
<not-authorized/> stanza error in response to the presence
probe.
2. Else, if the contact is blocking presence notifications to the
user's bare JID or full JID (using either a default list or
active list as defined under Blocking Outbound Presence
Notifications (Section 10.11)), the server MUST NOT reply to the
presence probe.
3. Else, if the contact has no available resources, the server MUST
either (1) reply to the presence probe by sending to the user the
full XML of the last presence stanza of type "unavailable"
received by the server from the contact, or (2) not reply at all.
4. Else, if the contact has at least one available resource, the
server MUST reply to the presence probe by sending to the user
the full XML of the last presence stanza received by the server
from each of the contact's available resources (again, subject to
privacy rules for each session).
Upon receiving initial presence from the user, the contact's server
MUST deliver the user's presence stanza to the full JIDs
(<contact@example.org/resource>) associated with all of the contact's
available resources, 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 under Blocking Inbound Presence Notifications
(Section 10.10)).
If the user's server receives a presence stanza of type "error" in
response to the initial presence that it sent to a contact on behalf
of the user, it SHOULD NOT send further presence updates to that
contact (until and unless it receives a presence stanza from the
contact).
After sending initial presence, the user MAY update its presence
information for broadcasting at any time during its 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 (as well as to any of the user's other available resources).
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 entities that fit the above description, 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
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 available 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 first sending initial
presence or after having sent unavailable presence broadcast
(i.e., the resource is active but not available), 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 <status/> 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
of the user's other available resources, as well as 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). Any presence stanza with no
'type' attribute and no 'to' attribute that is sent after sending
directed unavailable presence or broadcasted unavailable presence
MUST be broadcasted by the server to all subscribers.
5.2 Specifying Availability Status
A client MAY provide further information about its availability
status by using the <show/> element (see Show (Section 2.2.2.1)).
Example: Availability status:
<presence>
<show>dnd</show>
</presence>
5.3 Specifying Detailed Status Information
In conjunction with the <show/> element, a client MAY provide
detailed status information by using the <status/> element (see
Status (Section 2.2.2.2)).
Example: Detailed status information:
<presence xml:lang='en'>
<show>dnd</show>
<status>Wooing Juliet</status>
<status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
</presence>
5.4 Specifying Presence Priority
A client MAY provide a priority for its resource by using the
<priority/> element (see Priority (Section 2.2.2.3)).
Example: Presence priority:
<presence xml:lang='en'>
<show>dnd</show>
<status>Wooing Juliet</status>
<status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
<priority>1</priority>
</presence>
5.5 Presence Examples
The examples in this section illustrate the presence-related
protocols described above. The user is romeo@example.net, he has an
available resource whose resource identifier is "orchard", and he has
the following individuals in his roster:
o juliet@example.com (subscription="both" and she has two available
resources, one whose resource is "chamber" and another whose
resource is "balcony")
o benvolio@example.org (subscription="to")
o mercutio@example.org (subscription="from")
Example 1: User sends initial presence:
<presence/>
Example 2: User's server sends presence probes to contacts with
subscription="to" and subscription="both" on behalf of the user's
available resource:
<presence
type='probe'
from='romeo@example.net/orchard'
to='juliet@example.com'/>
<presence
type='probe'
from='romeo@example.net/orchard'
to='benvolio@example.org'/>
Example 3: User's server sends initial presence to contacts with
subscription="from" and subscription="both" on behalf of the user's
available resource:
<presence
from='romeo@example.net/orchard'
to='juliet@example.com'/>
<presence
from='romeo@example.net/orchard'
to='mercutio@example.org'/>
Example 4: Contacts' server replies to presence probe on behalf of
all of the contact's available resources:
<presence
from='juliet@example.com/balcony'
to='romeo@example.net/orchard'
xml:lang='en'>
<show>away</show>
<status>be right back</status>
<priority>0</priority>
</presence>
<presence
from='juliet@example.com/chamber'
to='romeo@example.net/orchard'>
<priority>1</priority>
</presence>
<presence
from='benvolio@example.org/pda'
to='romeo@example.net/orchard'
xml:lang='en'>
<show>dnd</show>
<status>gallivanting</status>
</presence>
Example 5: Contact's server delivers user's initial presence to all
of the contact's available resources or returns error to user:
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/chamber'/>
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/balcony'/>
<presence
type='error'
from='mercutio@example.org'
to='romeo@example.net/orchard'>
<error type='cancel'>
<gone xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</presence>
Example 6: User sends directed presence to another user not in his
roster:
<presence
from='romeo@example.net/orchard'
to='nurse@example.com'
xml:lang='en'>
<show>dnd</show>
<status>courting Juliet</status>
<priority>0</priority>
</presence>
Example 7: User sends updated available presence information for
broadcasting:
<presence xml:lang='en'>
<show>away</show>
<status>I shall return!</status>
<priority>1</priority>
</presence>
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):
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/chamber'
xml:lang='en'>
<show>away</show>
<status>I shall return!</status>
<priority>1</priority>
</presence>
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/balcony'
xml:lang='en'>
<show>away</show>
<status>I shall return!</status>
<priority>1</priority>
</presence>
Example 9: One of the contact's resources sends final presence:
<presence type='unavailable'/>
Example 10: Contact's server sends unavailable presence information
to user:
<presence
type='unavailable'
from='juliet@example.com/balcony'
to='romeo@example.net/orchard'/>
Example 11: User sends final presence:
<presence type='unavailable' xml:lang='en'>
<status>gone home</status>
</presence>
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:
<presence
type='unavailable'
from='romeo@example.net/orchard'
to='juliet@example.com/chamber'
xml:lang='en'>
<status>gone home</status>
</presence>
<presence
from='romeo@example.net/orchard'
to='nurse@example.com'
xml:lang='en'>
<status>gone home</status>
</presence>
6. 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 8), and the reader must refer to that
section for a complete understanding of presence subscriptions.
6.1 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:
<presence to='juliet@example.com' type='subscribe'/>
If the subscription request is being sent to an instant messaging
contact, the JID supplied in the 'to' attribute SHOULD be of the form
<contact@example.org> rather than <contact@example.org/resource>,
since the desired result is normally for the user to receive presence
from all of the contact's resources, not merely the particular
resource specified in the 'to' attribute.
A user's server MUST NOT automatically approve subscription requests
on the user's behalf. All subscription requests MUST be directed to
the user's client, specifically to one or more available resources
associated with the user. If there is no available resource
associated with the user when the subscription request is received by
the user's server, the user's server MUST keep a record of the
subscription request and deliver the request when the user next
creates an available resource, until the user either approves or
denies the request. If there is more than one available resource
associated with the user when the subscription request is received by
the user's server, the user's server MUST broadcast that subscription
request to all available resources in accordance with Server Rules
for Handling XML Stanzas (Section 11). (Note: If an active resource
has not provided initial presence, the server MUST NOT consider it to
be available and therefore MUST NOT send subscription requests to
it.) However, f the user receives a presence stanza of type
"subscribe" from a contact to whom the user has already granted
permission to see the user's presence (e.g., in cases when the
contact is seeking to resynchronize subscription states), the user's
server SHOULD auto-reply on behalf of the user.
6.2 Handling a Subscription Request
When a client receives a subscription request from another entity, it
MUST either approve the request by sending a presence stanza of type
"subscribed" or refuse the request by sending a presence stanza of
type "unsubscribed".
Example: Approving a subscription request:
<presence to='romeo@example.net' type='subscribed'/>
Example: Refusing a presence subscription request:
<presence to='romeo@example.net' type='unsubscribed'/>
6.3 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:
<presence to='romeo@example.net' type='unsubscribed'/>
6.4 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:
<presence to='juliet@example.com' type='unsubscribe'/>
7. Roster Management
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 <contact@example.org>). 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 resource.
Note: There are important interactions between rosters and
subscriptions; these are defined under Integration of Roster Items
and Presence Subscriptions (Section 8), and the reader must refer to
that section for a complete understanding of roster management.
7.1 Syntax and Semantics
Rosters are managed using IQ stanzas, specifically by means of a
<query/> child element qualified by the 'jabber:iq:roster' namespace.
The <query/> element MAY contain one or more <item/> children, each
describing a unique roster item or "contact".
The "key" or unique identifier for each roster item is a JID,
encapsulated in the required 'jid' attribute of the <item/> element.
The value of the 'jid' attribute SHOULD be of the form <user@domain>,
especially if the item is associated with another (human) instant
messaging user.
The state of the presence subscription in relation to a roster item
is captured in the 'subscription' attribute of the <item/> element.
Allowable values for this attribute are:
o "none" -- the user does not have a subscription to the contact,
and the contact does not have a subscription to the user
o "to" -- the user has a subscription to the contact, but the
contact does not have a subscription to the user
o "from" -- the contact has a subscription to the user, but the user
does not have a subscription to the contact
o "both" -- both the user and the contact have subscriptions to each
other
Each <item/> element MAY contain a 'name' attribute, which sets the
"nickname" to be associated with the JID, as determined by the user
(not the contact). The value of the 'name' attribute is opaque.
Each <item/> element MAY contain one or more <group/> child elements,
for use in collecting roster items into various categories. The
CDATA text of the <group/> element is opaque.
7.2 Business Rules
A server MUST ignore any 'to' address on a roster "set", and MUST
treat any roster "set" as applying to the sender. For added safety,
a client SHOULD check the "from" address of a roster "push" to ensure
that it is from a trusted source; specifically, the stanza MUST
either have no 'from' attribute (i.e., implicitly from the server) or
have a 'from' attribute whose value matches the user's bare JID (of
the form <user@domain>) or full JID (of the form <user@domain/
resource>); otherwise, the client SHOULD ignore the roster "push".
7.3 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 MUST NOT
send it presence subscriptions and associated roster updates.
Example: Client requests current roster from server:
<iq from='juliet@example.com/balcony' type='get' id='roster_1'>
<query xmlns='jabber:iq:roster'/>
</iq>
Example: Client receives roster from the server:
<iq to='juliet@example.com/balcony' type='result' id='roster_1'>
<query xmlns='jabber:iq:roster'>
<item jid='romeo@example.net'
name='Romeo'
subscription='both'>
<group>Friends</group>
</item>
<item jid='mercutio@example.org'
name='Mercutio'
subscription='from'>
<group>Friends</group>
</item>
<item jid='benvolio@example.org'
name='Benvolio'
subscription='both'>
<group>Friends</group>
</item>
</query>
</iq>
7.4 Adding a Roster Item
At any time, a user MAY add an item to his or her roster.
Example: Client adds a new item:
<iq from='juliet@example.com/balcony' type='set' id='roster_2'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com'
name='Nurse'>
<group>Servants</group>
</item>
</query>
</iq>
The server MUST update the roster information in persistent storage,
and also push the change out to all of the user's available resources
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 that have requested the roster and (2) replies
with an IQ result to the sending resource:
<iq to='juliet@example.com/balcony' type='set'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com'
name='Nurse'
subscription='none'>
<group>Servants</group>
</item>
</query>
</iq>
<iq to='juliet@example.com/chamber' type='set'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com'
name='Nurse'
subscription='none'>
<group>Servants</group>
</item>
</query>
</iq>
<iq to='juliet@example.com/balcony' type='result' id='roster_2'/>
Example: Connected resources reply with an IQ result to the server:
<iq from='juliet@example.com/balcony'
to='example.com'
type='result'/>
<iq from='juliet@example.com/chamber'
to='example.com'
type='result'/>
7.5 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.
Example: User updates roster item (added group):
<iq from='juliet@example.com/chamber' type='set' id='roster_3'>
<query xmlns='jabber:iq:roster'>
<item jid='romeo@example.net'
name='Romeo'
subscription='both'>
<group>Friends</group>
<group>Lovers</group>
</item>
</query>
</iq>
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.
7.6 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:
<iq from='juliet@example.com/balcony' type='set' id='roster_4'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com' subscription='remove'/>
</query>
</iq>
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
Removing a Roster Item and Cancelling All Subscriptions (Section
8.6).
8. Integration of Roster Items and Presence Subscriptions
8.1 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 instant messaging applications.
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.
Narrative explanations of how these subscription states interact with
roster items in order to complete certain defined use cases are
provided in the following sub-sections. Full details regarding
server and client handling of all subscription states (including
pending states between the primary states listed above) is provided
in Subscription States (Section 9).
If an active resource does not both send initial presence and request
the roster, the server MUST NOT send it presence subscription
requests or roster pushes.
The 'from' and 'to' addresses 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]).
8.2 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 perform a "roster set" for
the new roster item. This request consists of an IQ stanza of
type='set' containing a <query/> element in the
'jabber:iq:roster' namespace, which in turn contains an <item/>
element that defines the new roster item; the <item/> element
MUST possess a 'jid' attribute, MAY possess a 'name' attribute,
MUST NOT possess a 'subscription' attribute, and MAY contain one
or more <group/> child elements:
<iq type='set' id='set1'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
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 result related to the roster set:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<iq type='result' id='set1'/>
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:
<presence to='contact@example.org' type='subscribe'/>
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 sub-state is denoted by
the inclusion of the ask='subscribe' attribute in the roster
item:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
ask='subscribe'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
Note: If the user did not create a roster item before sending the
subscription request, the server MUST now create one on behalf of
the user with the 'subscription' attribute set to a value of
"none", then send a roster push to all of the user's available
resources that have requested the roster, absent the 'name'
attribute and the <group/> child.
5. The user's server MUST also stamp the presence stanza of type
"subscribe" with the user's bare JID (i.e., <user@example.com>)
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):
<presence
from='user@example.com'
to='contact@example.org'
type='subscribe'/>
Note: If the user's server receives a presence stanza of type
"error" from the contact's server in response to the outgoing
presence stanza of type "subscribe", it MUST revert the
subscription state from the new state ("None + Pending Out") to
the previous state ("None"), and MUST deliver the error stanza to
the user.
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 available resource from which the contact 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; normally this is done by adding a roster item for
the contact to the user's roster, with a state of "None + Pending
In" as defined under Subscription States (Section 9), however a
server SHOULD NOT push or deliver roster items in that state to
the user). No matter when the subscription request is delivered,
the contact must decide whether or not to approve it (subject to
configured preferences, the contact's client MAY approve or
refuse the subscription request without presenting it to the
contact). Here we assume the "happy path" that the contact
approves the subscription request (the alternate flow of
declining the subscription request is defined in Section 8.2.1).
In this case, the contact's client (1) SHOULD perform a roster
set specifying the desired nickname and group for the user (if
any); and (2) MUST send a presence stanza of type "subscribed" to
the user in order to approve the subscription request.
<iq type='set' id='set2'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence to='user@example.com' type='subscribed'/>
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' (the server MUST send this
even if the contact did not perform a roster set); (2) MUST
return an IQ result related to the roster set; (3) MUST route the
presence stanza of type "subscribed" to the user; and (4) MUST
send available presence from all of the contact's available
resources to the user:
<iq type='set' to='contact@example.org/resource'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='from'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<iq type='result' to='contact@example.org/resource' id='set2'/>
<presence
from='contact@example.org/resource'
to='user@example.com'
type='subscribed'/>
<presence
from='contact@example.org/resource'
to='user@example.com'/>
Note: If the contact's server receives a presence stanza of type
"error" from the user's server in response to the outgoing
presence stanza of type "subscribed", it MUST revert the
subscription state from the new state ("From") to the previous
state ("None + Pending In"), and MUST deliver the error stanza to
the contact.
8. Upon receiving the presence stanza of type "subscribed" addressed
to the user, the user's server MUST first verify that the contact
is in the user's roster with either of the following states: (a)
subscription='none' and ask='subscribe' or (b)
subscription='from' and 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:
<presence
to='user@example.com'
from='contact@example.org'
type='subscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='to'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='contact@example.org/resource'
to='user@example.com/resource'/>
9. Upon receiving the presence stanza of type "subscribed", the user
SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "subscribe" to the contact or "denying" it by
sending a presence stanza of type "unsubscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
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.)
8.2.1 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 refuses the user's subscription request.
1. If the contact wants to refuse 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 8.2):
<presence to='user@example.com' type='unsubscribed'/>
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 (<contact@example.org>) of the contact:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
Note: if the contact's server previously added the user to the
contact's roster for tracking purposes, it MUST remove the
relevant item at this time.
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:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
4. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
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.
8.3 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 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):
<presence to='user@example.com' type='subscribe'/>
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
(<contact@example.org>) of the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='from'
ask='subscribe'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='subscribe'/>
Note: If the contact's server receives a presence stanza of type
"error" from the user's server in response to the outgoing
presence stanza of type "subscribe", it MUST revert the
subscription state from the new state ("From + Pending Out") to
the previous state ("From"), and MUST deliver the error stanza to
the contact.
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 available resource for which the user 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 approve it (subject to
configured preferences, the user's client MAY approve or refuse
the subscription request without presenting it to the user).
Here we assume the "happy path" that the user approves the
subscription request (the alternate flow of declining the
subscription request is defined in Section 8.3.1). In this case,
the user's client MUST send a presence stanza of type
"subscribed" to the contact in order to approve the subscription
request.
<presence to='contact@example.org' type='subscribed'/>
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) MUST route
the presence stanza of type "subscribed" to the contact, first
stamping the 'from' address as the bare JID (<user@example.com>)
of the user; and (3) MUST send available presence from each of
the user's available resources to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='both'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='subscribed'/>
<presence
from='user@example.com/resource'
to='contact@example.org'/>
Note: If the user's server receives a presence stanza of type
"error" from the contact's server in response to the outgoing
presence stanza of type "subscribed", it MUST revert the
subscription state from the new state ("Both") to the previous
state ("To + Pending In"), and MUST deliver the error stanza to
the user.
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' and ask='subscribe' or (b)
subscription='from' and 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
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:
<presence
from='user@example.com'
to='contact@example.org'
type='subscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='both'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com/resource'
to='contact@example.org/resource'/>
6. Upon receiving the presence stanza of type "subscribed", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "subscribe" to the user or "denying" it by sending
a presence stanza of type "unsubscribe" to the user; this step
does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
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.)
8.3.1 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 refuses the contact's subscription request.
1. If the user wants to refuse 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 8.3):
<presence to='contact@example.org' type='unsubscribed'/>
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 (<user@example.com>) of the user:
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
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:
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='from'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
4. Upon receiving the presence stanza of type "unsubscribed", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the user or "denying" it by
sending a presence stanza of type "subscribe" to the user; this
step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
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".
8.4 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.
8.4.1 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:
<presence to='contact@example.org' type='unsubscribe'/>
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
(<user@example.com>) of the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
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) MUST
deliver the "unsubscribe" state change notification to the
contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='none'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
4. Upon receiving the presence stanza of type "unsubscribe", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribed" to the user or "denying" it by
sending a presence stanza of type "subscribed" to the user; this
step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
5. The contact's server then (1) MUST send a presence stanza of type
"unsubscribed" to the user; and (2) SHOULD send unavailable
presence from the contact to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
6. When the user's server receives a presence stanza of type
"unsubscribed" and/or unavailable presence, it MUST deliver them
to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
7. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
8.4.2 Case #2: Unsubscribing 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 user wants to unsubscribe from the contact's presence, the
user MUST send a presence stanza of type "unsubscribe" to the
contact:
<presence to='contact@example.org' type='unsubscribe'/>
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) MUST
route the presence stanza of type "unsubscribe" to the contact,
first stamping the 'from' address as the bare JID
(<user@example.com>) of the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='from'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
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) MUST deliver the
"unsubscribe" state change notification to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='to'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
4. Upon receiving the presence stanza of type "unsubscribe", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribed" to the user or "denying" it by
sending a presence stanza of type "subscribed" to the user; this
step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
5. The contact's server then (1) MUST send a presence stanza of type
"unsubscribed" to the user; and (2) SHOULD send unavailable
presence from the contact to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
6. When the user's server receives a presence stanza of type
"unsubscribed" and/or unavailable presence, it MUST deliver them
to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
7. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
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,
the user SHOULD update the roster item with subscription='remove' as
defined under Removing a Roster Item and Cancelling All Subscriptions
(Section 8.6).
8.5 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.
8.5.1 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:
<presence to='user@example.com' type='unsubscribed'/>
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
(<contact@example.org>) of the contact; and (3) SHOULD send
unavailable presence from the contact to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='none'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
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); (2) MUST deliver the "unsubscribed" state
change notification to the user; and (3) MUST deliver the
unavailable presence to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
4. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
8.5.2 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:
<presence to='user@example.com' type='unsubscribed'/>
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
(<contact@example.org>) of the contact; and (3) SHOULD send
unavailable presence from the contact to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='to'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
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) MUST deliver the "unsubscribed"
state change notification to the user; and (3) MUST deliver the
unavailable presence to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='from'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
4. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
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 under Removing a Roster Item and
Cancelling All Subscriptions (Section 8.6).
8.6 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, the
roster management protocol 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":
<iq type='set' id='remove1'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='remove'/>
</query>
</iq>
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 that have requested
the roster 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:
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='remove'/>
</query>
</iq>
<iq type='result' id='remove1'/>
<presence
from='user@example.com'
to='contact@example.org'
type='unavailable'/>
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) MUST also deliver the "unsubscribe" state change notification
to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='to'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
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) MUST also deliver the "unsubscribe" state change notification
to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='none'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
Upon receiving the presence stanza of type "unavailable" addressed to
the contact, the contact's server MUST deliver the unavailable
presence to the user:
<presence
from='user@example.com'
to='contact@example.org'
type='unavailable'/>
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.
9. Subscription States
This section provides detailed information about subscription states
and server handling of subscription-related presence stanzas (i.e.,
presence stanzas of type "subscribe", "subscribed", "unsubscribe",
and "unsubscribed").
9.1 Defined States
There are nine possible subscription states, which are described here
from the user's (not contact's) perspective:
1. "None" = contact and user are not subscribed to each other, and
neither has requested a subscription from the other
2. "None + Pending Out" = contact and user are not subscribed to
each other, and user has sent contact a subscription request but
contact has not replied yet
3. "None + Pending In" = contact and user are not subscribed to each
other, and contact has sent user a subscription request but user
has not replied yet (note: contact's server SHOULD NOT push or
deliver roster items in this state, but instead SHOULD wait until
contact has approved subscription request from user)
4. "None + Pending Out/In" = contact and user are not subscribed to
each other, contact has sent user a subscription request but user
has not replied yet, and user has sent contact a subscription
request but contact has not replied yet
5. "To" = user is subscribed to contact (one-way)
6. "To + Pending In" = user is subscribed to contact, and contact
has send user a subscription request but user has not replied yet
7. "From" = contact is subscribed to user (one-way)
8. "From + Pending Out" = contact is subscribed to user, and user
has sent contact a subscription request but contact has not
replied yet
9. "Both" = user and contact are subscribed to each other (two-way)
9.2 Server Handling of Outbound Presence Subscription Stanzas
Outbound presence subscription stanzas enable the user to manage his
or her subscription to the contact (via the "subscribe" and
"unsubscribe" types), and to manage the contact's access to the
user's presence information (via the "subscribed" and "unsubscribed"
types).
Because it is possible for the user's server and the contact's server
to lose synchronization regarding subscription states, the user's
server MUST route all outbound presence stanzas of type "subscribe"
or "unsubscribe" to the contact so that the user is able to
resynchronize his or her subscription to the contact if needed.
The user's server SHOULD NOT route a presence stanza of type
"subscribed" or "unsubscribed" to the contact if the stanza does not
result in a subscription state change from the user's perspective,
and MUST NOT make a state change. If the stanza results in a
subscription state change, the user's server MUST route the stanza to
the contact and MUST make the appropriate state change. These rules
are summarized in the following tables.
Table 1: Recommended handling of outbound "subscribed" stanzas
+----------------------------------------------------------------+
| EXISTING STATE | ROUTE? | NEW STATE |
+----------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | no | no state change |
| "None + Pending In" | yes | "From" |
| "None + Pending Out/In" | yes | "From + Pending Out" |
| "To" | no | no state change |
| "To + Pending In" | yes | "Both" |
| "From" | no | no state change |
| "From + Pending Out" | no | no state change |
| "Both" | no | no state change |
+----------------------------------------------------------------+
Table 2: Recommended handling of outbound "unsubscribed" stanzas
+----------------------------------------------------------------+
| EXISTING STATE | ROUTE? | NEW STATE |
+----------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | no | no state change |
| "None + Pending In" | yes | "None" |
| "None + Pending Out/In" | yes | "None + Pending Out" |
| "To" | no | no state change |
| "To + Pending In" | yes | "To" |
| "From" | yes | "None" |
| "From + Pending Out" | yes | "None + Pending Out" |
| "Both" | yes | "To" |
+----------------------------------------------------------------+
9.3 Server Handling of Inbound Presence Subscription Stanzas
Inbound presence subscription stanzas request a subscription-related
action from the user (via the "subscribe" type), inform the user of
subscription-related actions taken by the contact (via the
"unsubscribe" type), or enable the user to manage the contact's
access to the user's presence information (via the "subscribed" and
"unsubscribed" types).
When the user's server receives a subscription request for the user
from the contact (i.e., a presence stanza of type "subscribe"), it
MUST deliver that request to the user for approval if the user has
not already granted the contact access to the user's presence
information and if there is no pending inbound subscription request;
however, the user's server SHOULD NOT deliver the new request if
there is a pending inbound subscription request, since the previous
subscription request will have been recorded. If the user has
already granted the contact access to the user's presence
information, the user's server SHOULD auto-reply to an inbound
presense stanza of type "subscribe" from the contact by sending a
presence stanza of type "subscribed" to the contact on behalf of the
user; this rule enables the contact to resynchronize the subscription
state if needed. These rules are summarized in the following table.
Table 3: Recommended handling of inbound "subscribe" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | yes | "None + Pending In" |
| "None + Pending Out" | yes | "None + Pending Out/In" |
| "None + Pending In" | no | no state change |
| "None + Pending Out/In" | no | no state change |
| "To" | yes | "To + Pending In" |
| "To + Pending In" | no | no state change |
| "From" | no * | no state change |
| "From + Pending Out" | no * | no state change |
| "Both" | no * | no state change |
+------------------------------------------------------------------+
* Server SHOULD auto-reply with "subscribed" stanza
When the user's server receives a presence stanza of type
"unsubscribe" for the user from the contact, if the stanza results in
a subscription state change from the user's perspective then the
user's server SHOULD auto-reply by sending a presence stanza of type
"unsubscribed" to the contact on behalf of the user, MUST deliver the
"unsubscribe" stanza to the user, and MUST change the state. If no
subscription state change results, the user's server SHOULD NOT
deliver the stanza and MUST NOT change the state. These rules are
summarized in the following table.
Table 4: Recommended handling of inbound "unsubscribe" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | no | no state change |
| "None + Pending In" | yes * | "None" |
| "None + Pending Out/In" | yes * | "None + Pending Out" |
| "To" | no | no state change |
| "To + Pending In" | yes * | "To" |
| "From" | yes * | "None" |
| "From + Pending Out" | yes * | "None + Pending Out |
| "Both" | yes * | "To" |
+------------------------------------------------------------------+
* Server SHOULD auto-reply with "unsubscribed" stanza
When the user's server receives a presence stanza of type
"subscribed" for the user from the contact, it MUST NOT deliver the
stanza to the user and MUST NOT change the subscription state if
there is no pending outbound request for access to the contact's
presence information. If there is a pending outbound request for
access to the contact's presence information and the inbound presence
stanza of type "subscribed" results in a subscription state change,
the user's server MUST deliver the stanza to the user and MUST change
the subscription state. If the user already has access to the
contact's presence information, the inbound presence stanza of type
"subscribed" does not result in a subscription state change;
therefore the user's server SHOULD NOT deliver the stanza to the user
and MUST NOT change the subscription state. These rules are
summarized in the following table.
Table 5: Recommended handling of inbound "subscribed" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | yes | "To" |
| "None + Pending In" | no | no state change |
| "None + Pending Out/In" | yes | "To + Pending In" |
| "To" | no | no state change |
| "To + Pending In" | no | no state change |
| "From" | no | no state change |
| "From + Pending Out" | yes | "Both" |
| "Both" | no | no state change |
+------------------------------------------------------------------+
When the user's server receives a presence stanza of type
"unsubscribed" for the user from the contact, it MUST deliver the
stanza to the user and MUST change the subscription state if there is
a pending outbound request for access to the contact's presence
information or if the user currently has access to the contact's
presence information. Otherwise, the user's server SHOULD NOT
deliver the stanza and MUST NOT change the subscription state. These
rules are summarized in the following table.
Table 6: Recommended handling of inbound "unsubscribed" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | yes | "None" |
| "None + Pending In" | no | no state change |
| "None + Pending Out/In" | yes | "None + Pending In" |
| "To" | yes | "None" |
| "To + Pending In" | yes | "None + Pending In" |
| "From" | no | no state change |
| "From + Pending Out" | yes | "From" |
| "Both" | yes | "From" |
+------------------------------------------------------------------+
9.4 Server Delivery and Client Acknowledgement of Subscription State
Change Notifications
When a server receives an inbound presence stanza of type
"subscribe", "subscribed", "unsubscribe", or "unsubscribed" that
consists of a subscription state change request or notification, in
addition to sending the appropriate roster push (or updated roster
when the roster is next requested), it MUST deliver the request or
notification to the intended recipient at least once. A server MAY
require the recipient to acknowledge receipt of all state change
notifications (and MUST require acknowledgement in the case of
subscription requests, i.e., presence stanzas of type "subscribe").
In order to require acknowledgement, a server SHOULD send the
notification to the recipient each time the recipient logs in, until
the recipient acknowledges receipt of the notification by "affirming"
or "denying" the notification, as shown in the following table:
Table 7: Acknowledgement of subscription state change notifications
+--------------------------------------------------+
| STANZA TYPE | ACCEPT | DENY |
+--------------------------------------------------+
| subscribe | subscribed | unsubscribed |
| subscribed | subscribe | unsubscribe |
| unsubscribe | unsubscribed | subscribed |
| unsubscribed | unsubscribe | subscribe |
+--------------------------------------------------+
Obviously, given the foregoing subscription state charts, some of the
acknowledgement stanzas will be routed to the contact and result in
subscription state changes, while others will not. However, any such
stanzas MUST result in the server's no longer sending the
subscription state notification to the user.
Because a user's server MUST automatically generate outbound presence
stanzas of type "unsubscribe" and "unsubscribed" upon receiving a
roster set with the 'subscription' attribute set to a value of
"remove" (see Removing a Roster Item and Cancelling All Subscriptions
(Section 8.6)), the server MUST treat a roster remove request as
equivalent to sending both of those presence stanzas for purposes of
determining whether to continue sending subscription state change
notifications of type "subscribe" or "subscribed" to the user.
10. 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 [IMP-REQS]). 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 blocking messages based on JID, group, or subscription
type (or globally).
o Allowing or blocking inbound presence notifications based on JID,
group, or subscription type (or globally).
o Allowing or blocking outbound presence notifications based on JID,
group, or subscription type (or globally).
o Allowing or blocking IQs based on JID, group, or subscription type
(or globally).
o Allowing or blocking 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.
10.1 Syntax and Semantics
A user MAY define one or more privacy lists, which are stored by the
user's server. Each <list/> element contains one or more rules in
the form of <item/> elements, and each <item/> 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 processing order.
The syntax is as follows:
<iq>
<query xmlns='jabber:iq:privacy'>
<list name='foo'>
<item
type='[jid|group|subscription]'
value='bar'
action='[allow|deny]'
order='unsignedInt'>
[<message/>]
[<presence-in/>]
[<presence-out/>]
[<iq/>]
</item>
</list>
</query>
</iq>
If the type is "jid", then the 'value' attribute MUST contain a valid
Jabber ID. JIDs are matched in the following order: <user@domain/
resource>, then <user@domain>, then <domain/resource>, then <domain>.
If the value is <user@domain>, then any resource for that user@domain
matches. If the value is <domain/resource>, then only that resource
matches. If the value is <domain>, then any user@domain (or
subdomain) matches.
If the type is "group", then the 'value' attribute SHOULD 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 SHOULD return to the client an
<item-not-found/> stanza error.)
If the type is "subscription", then the 'value' attribute MUST be one
of "both", "to", "from", or "none" as defined under Roster Syntax and
Semantics (Section 7.1).
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 <bad-request/> stanza
error.)
The <item/> element MAY contain one or more child elements that
enable an entity to specify more granular control over which kinds of
stanzas are to be blocked (i.e., rather than blocking all stanzas).
The allowable child elements are:
o <message/> -- blocks incoming message stanzas
o <iq/> -- blocks incoming IQ stanzas
o <presence-in/> -- blocks incoming presence notifications
o <presence-out/> -- blocks outgoing presence notifications
Within the 'jabber:iq:privacy' namespace, the <query/> 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 <active/>
element, one <default/> element, or one <list/> element); if a client
violates this rule, the server MUST return to the client a
<bad-request/> stanza error.
When a client adds or updates a privacy list, the <list/> element
SHOULD contain at least one <item/> child element; when a client
removes a privacy list, the <list/> element SHOULD contain no <item/>
child element.
When a client updates a privacy list, it must include all of the
desired items (i.e., not a "delta").
10.2 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. The server MUST apply the active list only and
MUST NOT apply the default list.
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 MUST be the first rule applied by a server,
superseding (1) the routing and delivery rules specified in
Server Rules for Handling XML Stanzas (Section 11), and (2) the
handling of subscription-related presence stanzas (and
corresponding generation of roster pushes) specified in
Integration of Roster Items and Presence Subscriptions (Section
8).
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 integer values of the 'order' attribute
for each <item/>.
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. If a user updates the definition for an active list, subsequent
processing based on that active list MUST use the updated
definition (for all resources to which that active list
currently applies).
9. If a user modifies an active list by adding, modifying, or
deleting an item with the result that subsequent outbound
presence notifications will be blocked to certain subscribed
contacts, the server MUST also send unavailable presence from
the user to the affected contacts.
10. If a user modifies an active list by adding, modifying, or
deleting an item with the result that subsequent outbound
presence notifications will no longer be blocked to certain
subscribed contacts, the server MUST also send last available
presence from the user to the affected contacts.
11. If a change to the subscription state or roster group of a
roster item defined in an active or default list occurs during a
user's session, subsequent processing based on that list MUST
take into account the changed state or group (for all resources
to which that list currently applies).
10.3 Retrieving One's Privacy Lists
Example: Client requests names of privacy lists from server:
<iq from='romeo@example.org/orchard' type='get' id='getlist1'>
<query xmlns='jabber:iq:privacy'/>
</iq>
Example: Server sends names of privacy lists to client, preceded by
active list and default list:
<iq type='result' id='getlist1' to='romeo@example.net/orchard'>
<query xmlns='jabber:iq:privacy'>
<active name='private'/>
<default name='public'/>
<list name='public'/>
<list name='private'/>
<list name='special'/>
</query>
</iq>
Example: Client requests a privacy list from server:
<iq from='romeo@example.org/orchard' type='get' id='getlist2'>
<query xmlns='jabber:iq:privacy'>
<list name='public'/>
</query>
</iq>
Example: Server sends a privacy list to client:
<iq type='result' id='getlist2' to='romeo@example.net/orchard'>
<query xmlns='jabber:iq:privacy'>
<list name='public'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='1'/>
<item action='allow' order='2'/>
</list>
</query>
</iq>
Example: Client requests another privacy list from server:
<iq from='romeo@example.org/orchard' type='get' id='getlist3'>
<query xmlns='jabber:iq:privacy'>
<list name='private'/>
</query>
</iq>
Example: Server sends another privacy list to client:
<iq type='result' id='getlist3' to='romeo@example.net/orchard'>
<query xmlns='jabber:iq:privacy'>
<list name='private'>
<item type='subscription'
value='both'
action='allow'
order='10'/>
<item action='deny' order='15'/>
</list>
</query>
</iq>
Example: Client requests yet another privacy list from server:
<iq from='romeo@example.org/orchard' type='get' id='getlist4'>
<query xmlns='jabber:iq:privacy'>
<list name='special'/>
</query>
</iq>
Example: Server sends yet another privacy list to client:
<iq type='result' id='getlist4' to='romeo@example.net/orchard'>
<query xmlns='jabber:iq:privacy'>
<list name='special'>
<item type='jid'
value='juliet@example.com'
action='allow'
order='6'/>
<item type='jid'
value='benvolio@example.org'
action='allow'
order='7'/>
<item type='jid'
value='mercutio@example.org'
action='allow'
order='42'/>
<item action='deny' order='666'/>
</list>
</query>
</iq>
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 <item-not-found/> stanza error
to the user:
Example: Client attempts to retrieve non-existent list:
<iq to='romeo@example.org/orchard' type='error' id='getlist5'>
<query xmlns='jabber:iq:privacy'>
<list name='The Empty Set'/>
</query>
<error type='cancel'>
<item-not-found
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
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:
Example: Client attempts to retrieve more than one list:
<iq to='romeo@example.org/orchard' type='error' id='getlist6'>
<query xmlns='jabber:iq:privacy'>
<list name='public'/>
<list name='private'/>
<list name='special'/>
</query>
<error type='modify'>
<bad-request
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
10.4 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
<query/> element qualified by the 'jabber:iq:privacy' namespace that
contains an empty <active/> child element possessing a 'name'
attribute whose value is set to the desired list name.
Example: Client requests change of active list:
<iq from='romeo@example.org/orchard' type='set' id='active1'>
<query xmlns='jabber:iq:privacy'>
<active name='special'/>
</query>
</iq>
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:
<iq type='result' id='active1' to='romeo@example.org/orchard'/>
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:
Example: Client attempts to set a non-existent list as active:
<iq to='romeo@example.org/orchard' type='error' id='active2'>
<query xmlns='jabber:iq:privacy'>
<active name='The Empty Set'/>
</query>
<error type='cancel'>
<item-not-found
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
In order to decline the use of any active list, the user MUST send an
empty <active/> element with no name.
Example: Client declines the use of active lists:
<iq from='romeo@example.org/orchard' type='set' id='active2'>
<query xmlns='jabber:iq:privacy'>
<active/>
</query>
</iq>
10.5 Managing the Default List
In order to change its default list, the user MUST send an IQ stanza
of type "set" with a <query/> element qualified by the
'jabber:iq:privacy' namespace that contains an empty <default/> child
element possessing a 'name' attribute whose value is set to the
desired list name.
Example: Client requests change of default list:
<iq from='romeo@example.org/orchard' type='set' id='default1'>
<query xmlns='jabber:iq:privacy'>
<default name='special'/>
</query>
</iq>
Example: Server acknowledges success of default list change:
<iq type='result' id='default1' to='romeo@example.org/orchard'/>
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:
Example: Client attempts to set a non-existent list as default:
<iq to='romeo@example.org/orchard' type='error' id='default2'>
<query xmlns='jabber:iq:privacy'>
<default name='The Empty Set'/>
</query>
<error type='cancel'>
<item-not-found
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
In order to decline the use of a default list (i.e., to use the
domain's stanza routing rules at all times), the user MUST send an
empty <default/> element with no name.
Example: Client declines the use of the default list:
<iq from='romeo@example.org/orchard' type='set' id='default2'>
<query xmlns='jabber:iq:privacy'>
<default/>
</query>
</iq>
10.6 Editing a Privacy List
In order to edit a privacy list, the user MUST send an IQ stanza of
type "set" with a <query/> element qualified by the
'jabber:iq:privacy' namespace that contains one <list/> child element
possessing a 'name' attribute whose value is set to the list name the
user would like to edit. The <list/> element MUST contain one or
more <item/> 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:
<iq from='romeo@example.org/orchard' type='set' id='edit1'>
<query xmlns='jabber:iq:privacy'>
<list name='public'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='3'/>
<item type='jid'
value='paris@example.org'
action='deny'
order='5'/>
<item action='allow' order='68'/>
</list>
</query>
</iq>
Example: Server acknowledges success of list edit:
<iq type='result' id='edit1' to='juliet@example.com/balcony'/>
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@example.com" item and the
"paris@example.org" item, the user's client MUST renumber the
relevant items before submitting the list to the server.
10.7 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.
10.8 Removing a Privacy List
In order to remove a privacy list, the user MUST send an IQ stanza of
type "set" with a <query/> element qualified by the
'jabber:iq:privacy' namespace that contains one empty <list/> 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:
<iq from='romeo@example.org/orchard' type='set' id='remove1'>
<query xmlns='jabber:iq:privacy'>
<list name='private'/>
</query>
</iq>
Example: Server acknowledges success of list removal:
<iq type='result' id='remove1' to='juliet@example.com/balcony'/>
If a user attempts to remove an active list or the default list, the
server MUST return a <conflict/> 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 <item-not-found/> stanza error
to the user:
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.
10.9 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:
<iq from='romeo@example.org/orchard' type='set' id='msg1'>
<query xmlns='jabber:iq:privacy'>
<list name='message-jid-example'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='3'>
<message/>
</item>
</list>
</query>
</iq>
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:
<iq from='romeo@example.org/orchard' type='set' id='msg2'>
<query xmlns='jabber:iq:privacy'>
<list name='message-group-example'>
<item type='group'
value='Enemies'
action='deny'
order='4'>
<message/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive messages from any users in the specified roster
group.
Example: User blocks based on subscription type:
<iq from='romeo@example.org/orchard' type='set' id='msg3'>
<query xmlns='jabber:iq:privacy'>
<list name='message-sub-example'>
<item type='subscription'
value='none'
action='deny'
order='5'>
<message/>
</item>
</list>
</query>
</iq>
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:
<iq from='romeo@example.org/orchard' type='set' id='msg4'>
<query xmlns='jabber:iq:privacy'>
<list name='message-global-example'>
<item action='deny' order='6'>
<message/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive messages from any other users.
10.10 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 is currently subscribed to a contact's presence information.
Thus this includes presence stanzas with no 'type' attribute or of
type='unavailable' only.
Example: User blocks based on JID:
<iq from='romeo@example.org/orchard' type='set' id='presin1'>
<query xmlns='jabber:iq:privacy'>
<list name='presin-jid-example'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='7'>
<presence-in/>
</item>
</list>
</query>
</iq>
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:
<iq from='romeo@example.org/orchard' type='set' id='presin2'>
<query xmlns='jabber:iq:privacy'>
<list name='presin-group-example'>
<item type='group'
value='Enemies'
action='deny'
order='8'>
<presence-in/>
</item>
</list>
</query>
</iq>
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:
<iq from='romeo@example.org/orchard' type='set' id='presin3'>
<query xmlns='jabber:iq:privacy'>
<list name='presin-sub-example'>
<item type='subscription'
value='to'
action='deny'
order='9'>
<presence-in/>
</item>
</list>
</query>
</iq>
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.
Example: User blocks globally:
<iq from='romeo@example.org/orchard' type='set' id='presin4'>
<query xmlns='jabber:iq:privacy'>
<list name='presin-global-example'>
<item action='deny' order='11'>
<presence-in/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive presence notifications from any other users.
10.11 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 are currently subscribed to the user's presence
information. Thus this includes presence stanzas with no 'type'
attribute or of type='unavailable' only.
Example: User blocks based on JID:
<iq from='romeo@example.org/orchard' type='set' id='presout1'>
<query xmlns='jabber:iq:privacy'>
<list name='presout-jid-example'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='13'>
<presence-out/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not send presence notifications to the user with the specified
JID.
Example: User blocks based on roster group:
<iq from='romeo@example.org/orchard' type='set' id='presout2'>
<query xmlns='jabber:iq:privacy'>
<list name='presout-group-example'>
<item type='group'
value='Enemies'
action='deny'
order='15'>
<presence-out/>
</item>
</list>
</query>
</iq>
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:
<iq from='romeo@example.org/orchard' type='set' id='presout3'>
<query xmlns='jabber:iq:privacy'>
<list name='presout-sub-example'>
<item type='subscription'
value='from'
action='deny'
order='17'>
<presence-out/>
</item>
</list>
</query>
</iq>
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:
<iq from='romeo@example.org/orchard' type='set' id='presout4'>
<query xmlns='jabber:iq:privacy'>
<list name='presout-global-example'>
<item action='deny' order='23'>
<presence-out/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not send presence notifications to any other users.
10.12 Blocking IQs
Server-side privacy lists enable a user to block incoming IQ stanzas
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:
<iq from='romeo@example.org/orchard' type='set' id='iq1'>
<query xmlns='jabber:iq:privacy'>
<list name='iq-jid-example'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='29'>
<iq/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive IQ stanzas from the user with the specified JID.
Example: User blocks based on roster group:
<iq from='romeo@example.org/orchard' type='set' id='iq2'>
<query xmlns='jabber:iq:privacy'>
<list name='iq-group-example'>
<item type='group'
value='Enemies'
action='deny'
order='31'>
<iq/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive IQ stanzas from any users in the specified roster
group.
Example: User blocks based on subscription type:
<iq from='romeo@example.org/orchard' type='set' id='iq3'>
<query xmlns='jabber:iq:privacy'>
<list name='iq-sub-example'>
<item type='subscription'
value='none'
action='deny'
order='17'>
<iq/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive IQ stanzas from any users with the specified
subscription type.
Example: User blocks globally:
<iq from='romeo@example.org/orchard' type='set' id='iq4'>
<query xmlns='jabber:iq:privacy'>
<list name='iq-global-example'>
<item action='deny' order='1'>
<iq/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive IQ stanzas from any other users.
10.13 Blocking All Communication
Server-side privacy lists enable a user to block all stanzas from and
to other users based on the other user's JID, roster group, or
subscription status (or globally). Note that this includes
subscription-related presence stanzas, which are excluded by Blocking
Inbound Presence Notifications (Section 10.10). The following
examples illustrate the protocol.
Example: User blocks based on JID:
<iq from='romeo@example.org/orchard' type='set' id='all1'>
<query xmlns='jabber:iq:privacy'>
<list name='all-jid-example'>
<item type='jid'
value='tybalt@example.com'
action='deny'
order='23'/>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive any communications from, nor send any stanzas to,