Network Working Group P. Saint-Andre, Ed. Internet-Draft XMPP Standards Foundation Obsoletes: 3921 (if approved) July 17, 2007 Intended status: Standards Track Expires: January 18, 2008 Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence draft-saintandre-rfc3921bis-03 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 January 18, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document describes extensions to the core features of the Extensible Messaging and Presence Protocol (XMPP) that provide basic instant messaging (IM) and presence functionality in conformance with RFC 2779. This document obsoletes RFC 3921. Saint-Andre Expires January 18, 2008 [Page 1]
Internet-Draft XMPP IM July 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Typical Session Flow . . . . . . . . . . . . . . . . . . . 5 1.4. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6 2. Managing the Roster . . . . . . . . . . . . . . . . . . . . . 6 2.1. Syntax and Semantics . . . . . . . . . . . . . . . . . . . 6 2.2. Retrieving the Roster on Login . . . . . . . . . . . . . . 9 2.3. Adding a Roster Item . . . . . . . . . . . . . . . . . . . 10 2.4. Updating a Roster Item . . . . . . . . . . . . . . . . . . 15 2.5. Deleting a Roster Item . . . . . . . . . . . . . . . . . . 17 3. Managing Presence Subscriptions . . . . . . . . . . . . . . . 18 3.1. Requesting a Subscription . . . . . . . . . . . . . . . . 18 3.2. Cancelling a Subscription . . . . . . . . . . . . . . . . 24 3.3. Unsubscribing . . . . . . . . . . . . . . . . . . . . . . 26 4. Exchanging Presence Information . . . . . . . . . . . . . . . 27 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.2. Initial Presence . . . . . . . . . . . . . . . . . . . . . 28 4.3. Presence Probes . . . . . . . . . . . . . . . . . . . . . 30 4.4. Subsequent Presence Broadcast . . . . . . . . . . . . . . 32 4.5. Unavailable Presence . . . . . . . . . . . . . . . . . . . 34 4.6. Directed Presence . . . . . . . . . . . . . . . . . . . . 36 4.7. Presence Syntax . . . . . . . . . . . . . . . . . . . . . 37 5. Exchanging Messages . . . . . . . . . . . . . . . . . . . . . 41 5.1. Attributes . . . . . . . . . . . . . . . . . . . . . . . . 41 5.2. Child Elements . . . . . . . . . . . . . . . . . . . . . . 43 5.3. Extended Content . . . . . . . . . . . . . . . . . . . . . 45 6. Exchanging IQ Stanzas . . . . . . . . . . . . . . . . . . . . 46 7. A Sample Session . . . . . . . . . . . . . . . . . . . . . . . 46 8. Server Rules for Processing XML Stanzas . . . . . . . . . . . 52 8.1. No Such User . . . . . . . . . . . . . . . . . . . . . . . 53 8.2. Full JID at Local Domain . . . . . . . . . . . . . . . . . 53 8.3. Bare JID at Local Domain . . . . . . . . . . . . . . . . . 53 8.4. Foreign Domain . . . . . . . . . . . . . . . . . . . . . . 56 9. IM and Presence Compliance Requirements . . . . . . . . . . . 57 9.1. Servers . . . . . . . . . . . . . . . . . . . . . . . . . 57 9.2. Clients . . . . . . . . . . . . . . . . . . . . . . . . . 57 10. Internationalization Considerations . . . . . . . . . . . . . 58 11. Security Considerations . . . . . . . . . . . . . . . . . . . 58 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59 12.1. Instant Messaging SRV Protocol Label Registration . . . . 59 12.2. Presence SRV Protocol Label Registration . . . . . . . . . 59 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 60 13.1. Normative References . . . . . . . . . . . . . . . . . . . 60 13.2. Informative References . . . . . . . . . . . . . . . . . . 60 Appendix A. Subscription States . . . . . . . . . . . . . . . . . 61 Saint-Andre Expires January 18, 2008 [Page 2]
Internet-Draft XMPP IM July 2007 A.1. Defined States . . . . . . . . . . . . . . . . . . . . . . 62 A.2. Server Processing of Outbound Presence Subscription Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 63 A.3. Server Processing of Inbound Presence Subscription Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 65 Appendix B. Blocking Communication . . . . . . . . . . . . . . . 68 Appendix C. vCards . . . . . . . . . . . . . . . . . . . . . . . 68 Appendix D. XML Schemas . . . . . . . . . . . . . . . . . . . . . 68 D.1. jabber:client . . . . . . . . . . . . . . . . . . . . . . 69 D.2. jabber:server . . . . . . . . . . . . . . . . . . . . . . 73 D.3. jabber:iq:roster . . . . . . . . . . . . . . . . . . . . . 77 Appendix E. Differences From RFC 3921 . . . . . . . . . . . . . . 78 Appendix F. Copying Conditions . . . . . . . . . . . . . . . . . 78 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 80 Intellectual Property and Copyright Statements . . . . . . . . . . 81 Saint-Andre Expires January 18, 2008 [Page 3]
Internet-Draft XMPP IM July 2007 1. Introduction 1.1. Overview The Extensible Messaging and Presence Protocol (XMPP) is a technology for streaming Extensible Markup Language [XML] elements in order to exchange messages, presence information, and other structured data in close to real time. The core features of XMPP are defined in [XMPP-CORE]. These features -- mainly XML streams, use of Transport Layer Security ([TLS]) and Simple Authentication and Security Layer ([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 (see [XML-NAMES]). This document describes extensions to the core features of XMPP that provide the basic functionality expected of an instant messaging (IM) and presence application as defined in [IMP-REQS]. This document obsoletes RFC 3921. 1.2. Requirements Traditionally, instant messaging applications have combined the following factors: 1. The central point of focus is a list of one's contacts or "buddies" (in XMPP this list is called a ROSTER). 2. The purpose of using such an application is to exchange relatively brief text messages with each of one's contacts in close to real time -- often relatively large numbers of such messages in rapid succession, in the form of one-to-one "chat sessions". 3. The catalyst for exchanging messages is PRESENCE -- i.e., knowledge about the network availability of each of one's contacts (thus knowing who is online and available for a chat session). 4. Presence information is provided only to contacts that a user has authorized via a presence subscription. Thus at a high level this document assumes that a user must be able to complete the following use cases: o Manage items in a contact list o Exchange messages with one's contacts o Exchange presence information with one's contacts Saint-Andre Expires January 18, 2008 [Page 4]
Internet-Draft XMPP IM July 2007 o Manage presence subscriptions to and from one's contacts Detailed definitions of these functionality areas are contained in [IMP-REQS], and the interested reader should refer to that document regarding the requirements addressed herein. While the XMPP instant messaging and presence extensions specified herein meet the requirements of [IMP-REQS], they were 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. Although XMPP protocol extensions addressing many other functionality areas have been defined in the XMPP Standards Foundation's XEP series (e.g., multi-user text chat as specified in [XEP-0045]), such extensions are not included in this document because they are not required by [IMP-REQS]. Note: [IMP-REQS] stipulates that presence services must be separable from instant messaging services and vice-versa; 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 document 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. (For example, a presence-only service could return <service-unavailable/> errors if clients attempt to send <message/> stanzas.) 1.3. Typical Session Flow [XMPP-CORE] specifies how an XMPP client connects to an XMPP server. In particular, it specifies the preconditions (including XML stream establishment, authentication, and binding of a resource to the stream) that must be fulfilled before a client is allowed to send XML stanzas (the basic unit of meaning in XMPP) to other entities on an XMPP network. The reader is referred to [XMPP-CORE] for details, and knowledge of [XMPP-CORE] is assumed herein. Upon fulfillment of the preconditions specified in [XMPP-CORE], an XMPP client has a long-lived XML stream with an XMPP server, which enables the user to send and receive a potentially unlimited number of XML stanzas over the stream. Such a stream can be used as the basis for the exchange of instant messaging, presence, and other information in close to real time. The typical flow for an instant messaging and presence session is as follows: Saint-Andre Expires January 18, 2008 [Page 5]
Internet-Draft XMPP IM July 2007 1. Negotiate an XML stream with one's server. (See [XMPP-CORE].) 2. Retrieve one's roster. (See Section 2.2.) 3. Send initial presence to the server for broadcasting to all subscribed contacts, thus "going online" from the perspective of XMPP communications. (See Section 4.2.) 4. Exchange messages, manage presence subscriptions, perform roster updates, and in general process and generate other XML stanzas with particular semantics throughout the life of the session. (See Section 5 and Section 6.) 5. Terminate the session when desired by sending unavailable presence and closing the underlying XML stream. (See Section 4.5.) 1.4. Conventions This document inherits the terminology defined in [XMPP-CORE]. The following keywords are to be interpreted as described in [TERMS]: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL". For convenience, this document employs the term "user" to refer to the owner of an XMPP account; however, account owners need not be human persons and may be bots, devices, or other non-human applications. In examples, lines have been wrapped for improved readability, "[...]" means elision, and the following prepended strings are used: o C: = client o CC: = contact's client o CS: = contact's server o S: = server o UC: = user's client o US: = user's server 2. Managing the Roster In XMPP, one's roster contains any number of specific contacts. 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. 2.1. 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 detailed syntax and semantics are defined in the following Saint-Andre Expires January 18, 2008 [Page 6]
Internet-Draft XMPP IM July 2007 sections. 2.1.1. Items The <query/> element MAY contain one or more <item/> children, each describing a unique roster item or "contact". The syntax of the <item/> is as follows: 1. The 'jid' attribute is REQUIRED; the value of this attribute is a unique identifier or "key" for each roster item is a Jabber Identifier or JID. (Note: When the item added represents another IM user, the value of the 'jid' attribute MUST be a bare JID <contact@domain> rather a full JID <contact@domain/resource>, since the desired result is for the user to receive presence from all of the contact's resources, not merely the particular resource specified in the 'to' attribute.) 2. The 'name' attribute is OPTIONAL; the value of this attribute specifies the "handle" to be associated with the JID, as determined by the user (not the contact). The value of the 'name' attribute is opaque to the server but may have meaning to a human user. 3. The 'subscription' attribute is OPTIONAL; see Section 2.1.3. 4. The 'ask' attribute is OPTIONAL and is used to specify certain subscription sub-states; for details, see Section 3.1.2. 5. The <group/> element is OPTIONAL; the XML character of this element specifies a category into which the roster item should be grouped by a client. The <item/> MAY more than one <group/> element. The XML character data of the <group/> element has no meaning to the server but may have meaning to a human user. 2.1.2. Actions 2.1.2.1. Roster Get A ROSTER GET is an IQ stanza of type "get" sent from client to server and containing a <query/> element qualified by the 'jabber:iq:roster' namespace. The <query/> element in a roster get MUST NOT contain any <item/> child elements. 2.1.2.2. Roster Set A ROSTER SET is an IQ stanza of type "set" sent from client to server and containing a <query/> element qualified by the 'jabber:iq:roster' namespace. Saint-Andre Expires January 18, 2008 [Page 7]
Internet-Draft XMPP IM July 2007 The following rules apply to roster sets: 1. The <query/> element MUST contain one and only one <item/> element. 2. A receiving server MUST ignore any value of the 'subscription' attribute other than "remove" (see Section 2.1.3). 3. A receiving server MUST ignore any 'to' address specified on the IQ stanza and MUST handle the IQ stanza as if it included no 'to' attribute. 2.1.2.3. Roster Push A ROSTER PUSH is an IQ stanza of type "set" sent from server to client and containing a <query/> element qualified by the 'jabber:iq: roster' namespace. The following rules apply to roster pushes: 1. The <query/> element in a roster get MUST contain one and only one <item/> element. 2. A receiving client MUST ignore the stanza unless it has no 'from' attribute (i.e., implicitly from the server) or it has a 'from' attribute whose value matches the user's bare JID <user@domain>. 2.1.2.4. Roster Result A ROSTER RESULT is an IQ stanza of type "result" sent from server to client and containing a <query/> element qualified by the 'jabber:iq: roster' namespace. The <query/> element in a roster result contains one <item/> element for each roster item and therefore MAY contain more than one <item/> element. 2.1.3. Subscription Attribute The state of the presence subscription in relation to a roster item is captured in the 'subscription' attribute of the <item/> element. Allowable subscription-related values for this attribute are: o "none" -- the user does not have a subscription to the contact's presence information, and the contact does not have a subscription to the user's presence information o "to" -- the user has a subscription to the contact's presence information, but the contact does not have a subscription to the user's presence information Saint-Andre Expires January 18, 2008 [Page 8]
Internet-Draft XMPP IM July 2007 o "from" -- the contact has a subscription to the user's presence information, but the user does not have a subscription to the contact's presence information o "both" -- both the user and the contact have subscriptions to each other's presence information (also called a "mutual subscription") In a roster push or result, a receiving client MUST ignore values of the 'subscription' attribute other than "none", "to", "from", or "both". In a roster set, the value of the 'subscription' attribute MAY be "remove", which indicates that the item is to be removed from the roster; a receiving server MUST ignore all values of the 'subscription' attribute other than "remove". 2.2. Retrieving the Roster on Login Upon authenticating with a server and binding a resource (thus becoming a connected resource), a client SHOULD request the roster before sending initial presence (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 recommended and not required). After a connected resource sends initial presence (see Section 4.2), it is referred to as an available resource. If a connected resource requests the roster but does not send initial presence, the server SHOULD NOT send it presence subscriptions and SHOULD NOT send it associated roster pushes. If an available resource does not request the roster during a session, the server SHOULD NOT send it presence subscriptions and MUST NOT associated roster pushes. For the sake of brevity, the term INTERESTED RESOURCE is used herein to refer to the concept of "an available resource that has requested the roster". A client requests the roster by sending a roster get over its stream to the server. C: <iq from='juliet@example.com/balcony' type='get' id='roster_1'> <query xmlns='jabber:iq:roster'/> </iq> Saint-Andre Expires January 18, 2008 [Page 9]
Internet-Draft XMPP IM July 2007 S: <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'/> <item jid='nurse@example.com' name='Nurse' subscription='to'/> <item jid='benvolio@example.org' name='Benvolio' subscription='both'/> </query> </iq> If the server cannot process the roster get, it MUST return an appropriate stanza error as described in [XMPP-CORE] (such as <service-unavailable/> if the roster namespace is not supported or <internal-server-error/> if the server experiences trouble returning the roster). 2.3. Adding a Roster Item 2.3.1. Success Case At any time, a client may add an item to the roster by sending a roster set to the server. C: <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> If the server can successfully process the roster set (i.e., if none of the error cases occurs), it MUST create the roster item in persistent storage and send a roster push to all of the user's interested resources containing the new roster item. Saint-Andre Expires January 18, 2008 [Page 10]
Internet-Draft XMPP IM July 2007 S: <iq to='juliet@example.com/balcony' type='set' id='a78b4q6ha463'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='Nurse' subscription='none'> <group>Servants</group> </item> </query> </iq> S: <iq to='juliet@example.com/chamber' type='set' id='a78b4q6ha464'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='Nurse' subscription='none'> <group>Servants</group> </item> </query> </iq> The server MUST also return an IQ stanza of type "result" to the connected resource that sent the roster set. S: <iq to='juliet@example.com/balcony' type='result' id='roster_2'/> As required by the semantics of the IQ stanza kind as defined in [XMPP-CORE], each resource that received the roster push MUST reply with an IQ stanza of type "result" (or "error"). C: <iq from='juliet@example.com/balcony' type='result' id='a78b4q6ha463'/> C: <iq from='juliet@example.com/chamber' type='result' id='a78b4q6ha464'/> Note: There is no error case for client replies to roster pushes, and if the server receives an IQ of type "error" in response to a roster push it SHOULD ignore the error. 2.3.2. Error Cases If the server cannot successfully process the roster set, it MUST return an error. The following error cases are defined (naturally, Saint-Andre Expires January 18, 2008 [Page 11]
Internet-Draft XMPP IM July 2007 other stanza errors may occur, e.g., <internal-server-error/>). The server SHOULD return a <bad-request/> error to the client if the roster set violates any of the following conditions: 1. The <query/> element contains more than one <item/> child element. 2. The <item/> element contains more than one <group/> element, but there are duplicates among the XML character data of each <group/> element (where duplicates are determined using the Resourceprep profile of stringprep as defined in [XMPP-CORE]). The server SHOULD return a <not-allowed/> error to the client if the roster set violates any of the following conditions: 1. The value of the 'name' attribute is greater than a server- configured limit. 2. The XML character data of the <group/> element is of zero length. 3. The XML character data of the <group/> element is greater than a server-configured limit. Alternatively, the server MAY ignore the foregoing violations and process the roster set as best as possible (e.g., process only the first <item/> element, ignore duplicate <group/> elements, place the roster item in no group or a default group if the <group/> element is empty, and truncate 'name' attributes and <group/> elements that are too long). Error: Roster set contains more than one item C: <iq from='juliet@example.com/balcony' type='set' id='roster_3'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='Nurse'> <group>Servants</group> </item> <item jid='mother@example.com' name='Mom'> <group>Family</group> </item> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='roster_3'> <error type='modify'> <bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> Saint-Andre Expires January 18, 2008 [Page 12]
Internet-Draft XMPP IM July 2007 Error: Roster set contains item with oversized handle C: <iq from='juliet@example.com/balcony' type='set' id='roster_4'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='__some-very-long-handle__'> <group>Servants</group> </item> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='roster_4'> <error type='modify'> <not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> Error: Roster set contains duplicate groups C: <iq from='juliet@example.com/balcony' type='set' id='roster_5'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='Nurse'> <group>Servants</group> <group>Servants</group> </item> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='roster_5'> <error type='modify'> <bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> Saint-Andre Expires January 18, 2008 [Page 13]
Internet-Draft XMPP IM July 2007 Error: Roster set contains empty group C: <iq from='juliet@example.com/balcony' type='set' id='roster_6'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='Nurse'> <group></group> </item> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='roster_6'> <error type='modify'> <not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> Error: Roster set contains oversized group C: <iq from='juliet@example.com/balcony' type='set' id='roster_7'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' name='Nurse'> <group>__some-very-long-group-name__</group> </item> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='roster_7'> <error type='modify'> <not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> The server MUST return a <not-allowed/> error to the client if the value of the <item/> element's 'jid' attribute matches the bare JID <node@domain> portion of the <iq/> element's 'from' attribute. Saint-Andre Expires January 18, 2008 [Page 14]
Internet-Draft XMPP IM July 2007 Error: Roster set contains sender's JID C: <iq from='juliet@example.com/balcony' type='set' id='roster_8'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com'/> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='roster_8'> <error type='cancel'> <not-allowed xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> 2.4. Updating a Roster Item 2.4.1. Success Case Updating an existing roster item is done in the same way as adding a new roster item, i.e., by sending a roster set to the server. Because a roster item is atomic, the item shall be updated exactly as provided in the roster set. There are several reasons why a client might update a roster item: 1. Adding a group 2. Deleting a group 3. Changing the handle 4. Deleting the handle Consider a roster item that is defined as follows: <item jid='romeo@example.net' name='Romeo'> <group>Friends</group> </item> The user who has this item in her roster may want to add the item to another group. C: <iq from='juliet@example.com/chamber' type='set' id='update_1'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' name='Romeo'> <group>Friends</group> <group>Lovers</group> </item> </query> Saint-Andre Expires January 18, 2008 [Page 15]
Internet-Draft XMPP IM July 2007 </iq> The user may then want to remove the item from the original group. C: <iq from='juliet@example.com/chamber' type='set' id='update_2'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' name='Romeo'> <group>Lovers</group> </item> </query> </iq> The user may then want to change the handle for the item. C: <iq from='juliet@example.com/chamber' type='set' id='update_3'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' name='MyRomeo'> <group>Lovers</group> </item> </query> </iq> The user may then want to remove the handle altogether (note: including an empty 'name' attribute is equivalent to including no 'name' attribute). C: <iq from='juliet@example.com/chamber' type='set' id='update_4'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' name=''> <group>Lovers</group> </item> </query> </iq> The user may then want to remove the item from all groups. C: <iq from='juliet@example.com/chamber' type='set' id='update_5'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net'/> </query> </iq> As with adding a roster item, when updating a roster item the server MUST update the roster information in persistent storage, send a roster push to all of the user's interested resources, and send an IQ Saint-Andre Expires January 18, 2008 [Page 16]
Internet-Draft XMPP IM July 2007 result to the initiating resource; for details, see Section 2.3. 2.4.2. Error Cases The error cases described under Section 2.3 also apply to updating a roster item. 2.5. Deleting a Roster Item 2.5.1. Success Case At any time, a client may delete an item from his or her roster by sending roster set and setting the value of the 'subscription' attribute to "remove". C: <iq from='juliet@example.com/balcony' type='set' id='delete_1'> <query xmlns='jabber:iq:roster'> <item jid='nurse@example.com' subscription='remove'/> </query> </iq> As with adding a roster item, if the server can successfully process the roster set then it MUST update the roster information in persistent storage, send a roster push to all of the user's interested resources (with the 'subscription' attribute set to a value of "remove"), and send an IQ result to the initiating resource; for details, see Section 2.3. The server MUST also generate a presence stanza of type "unsubscribe" and a presence stanza of type "unsubscribed" from the user to the contact. S: <presence from='juliet@example.com' to='nurse@example.com' type='unsubscribe'/> S: <presence from='juliet@example.com' to='nurse@example.com' type='unsubscribed'/> 2.5.2. Error Cases If the value of the 'jid' attribute specifies an item that is not in the roster, the server MUST return an <item-not-found/> error. Saint-Andre Expires January 18, 2008 [Page 17]
Internet-Draft XMPP IM July 2007 Error: Roster item not found C: <iq from='juliet@example.com/balcony' type='set' id='delete_2'> <query xmlns='jabber:iq:roster'> <item jid='__no-such-user__@example.com' subscription='remove'/> </query> </iq> S: <iq to='juliet@example.com/balcony' type='error' id='delete_2'> <error type='modify'> <item-not-found xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> </error> </iq> 3. Managing Presence Subscriptions In order to protect the privacy of instant messaging users, presence 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. An entity that has a subscription to a user's presence (or to which a user has a presence subscription) is called a CONTACT. A subscription lasts across sessions; indeed, it lasts until the contact unsubscribes or the user cancels the previously- granted subscription. Subscriptions are managed within XMPP by sending presence stanzas containing specially-defined attributes ("subscribe", "unsubscribe", "subscribed", and "unsubscribed"). Note: When a user or contact generates a presence stanza of type "subscribe", "subscribed", "unsubscribe", and "unsubscribed" or a server processes or generates such a stanza on behalf of a user or contact, the server MUST stamp the outgoing presence stanza with the bare JID <node@domain> of the user or contact, not the full JID <node@domain/resource>. This rule helps to prevent presence leaks; for details, see the security considerations of [XMPP-CORE].) 3.1. Requesting a Subscription A SUBSCRIPTION REQUEST is a presence stanza whose 'type' attribute has a value of "subscribe". A subscription request is generated by a user's client, processed by the (potential) contact's server, and acted on by the contact via the contact's client. The workflow is described in the following sections. Saint-Andre Expires January 18, 2008 [Page 18]
Internet-Draft XMPP IM July 2007 3.1.1. Client Generation of Outbound Subscription Request A user's client generates a subscription request by sending a presence stanza of type "subscribe" and specifying a 'to' address of the potential contact's bare JID <contact@domain>. UC: <presence to='juliet@example.com' type='subscribe'/> Typically the user's client prompts the user for information about the potential contact ("handle" and desired roster group) and generates a roster set with that information before sending the subscription request, but that behavior is recommended rather than required. 3.1.2. Server Processing of Outbound Subscription Request As mentioned, the user's server MUST stamp the outbound subscription request with the bare JID <user@domain> of the user. US: <presence from='romeo@example.net' to='juliet@example.com' type='subscribe'/> If the potential contact is hosted on the same server, the server MUST adhere to the rules specified in the next section in processing the subscription request and delivering it to the (local) contact. If the potential contact is hosted on a different server, the user's server then routes the stanza to that foreign domain in accordance with core XMPP stanza processing rules. The user's server MUST then send a roster push to all of the user's interested resources, containing the potential contact with a subscription state of "none" and with notation that the subscription is pending (via an 'ask' attribute whose value is "subscribe"). Saint-Andre Expires January 18, 2008 [Page 19]
Internet-Draft XMPP IM July 2007 US: <iq to='romeo@example.net/foo' type='set' id='b89c5r7ib574'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='none' ask='subscribe'/> </query> </iq> US: <iq to='romeo@example.net/bar' type='set' id='b89c5r7ib575'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='none' ask='subscribe'/> </item> </query> </iq> Note: Because the server must send this roster push, a client MAY simply wait for the roster push rather than proactively adding the contact to the user's roster before sending the subscription request. 3.1.3. Server Processing of Inbound Subscription Request The contact's server MUST adhere to the following rules when processing the inbound subscription request: 1. Above all, the contact's server MUST NOT automatically approve subscription requests on the contact's behalf; instead, if a subscription request requires approval then the contact's server MUST deliver that request to the contact's interested resource(s) for approval or denial by the contact. 2. If the contact does not exist, the contact's server MUST automatically return a presence stanza of type "unsubscribed" to the user. CS: <presence from='juliet@example.com' to='romeo@example.net' type='unsubscribed'/> 3. If the contact exists and the user already has a subscription to the user's presence, the contact's server SHOULD auto-reply on behalf of the user by sending a presence stanza of type "subscribed" from the contact's bare JID to the user's bare JID. Saint-Andre Expires January 18, 2008 [Page 20]
Internet-Draft XMPP IM July 2007 4. If the contact exists, the user does not already have a subscription to the contact's presence, and there is at least one interested resource associated with the contact when the subscription request is received by the contact's server, the contact's server MUST broadcast that subscription request to all interested resources in accordance with Server Rules for Processing XML Stanzas (Section 8). 5. If the contact exists, the user does not already have a subscription to the contact's presence, and the contact has no interested resources when the subscription request is received by the contact's server, the contact's server MUST keep a record of the complete presence stanza comprising the subscription request, including any extended content contained therein, and deliver the request when the contact next has an interested resource, until the contact either approves or denies the request. (Note: The contact's server MUST NOT deliver more than one subscription request from any given user when the contact next has an interested resource; e.g., if the user sends multiple subscription requests to the contact while the contact is offline, the contact's server SHOULD store only one of those requests, such as the first request or last request, and MUST deliver only one of the requests when the contact next has an interested resource; this helps to prevent "subscription request spam".) Note: If the contact does not approve or deny the subscription request within some configurable amount of time, the user's server MAY choose to re-send the subscription request to the contact based on an implementation-specific algorithm (e.g., whenever a new resource becomes available for the user, or after a certain amount of time has elapsed); this helps to recover from transient, silent errors that may have occurred in relation to the original subscription request. 3.1.4. Client Processing of Inbound Subscription Request When the contact's client receives a subscription request from the user, it MUST present the request to the contact for approval (unless the contact has explicitly configured the client to automatically approve or deny some or all subscription requests). A subscription request is approved by sending a presence stanza of type "subscribed". CC: <presence to='romeo@example.net' type='subscribed'/> Note: Server processing of presence stanzas of type 'subscribed' is described in the following sections for both the contact's server and Saint-Andre Expires January 18, 2008 [Page 21]
Internet-Draft XMPP IM July 2007 the user's server. A subscription request is denied by sending a presence stanza of type "unsubscribed". CC: <presence to='romeo@example.net' type='unsubscribed'/> Note: Server processing of presence stanzas of type 'unsubscribed' is described under Section 3.2 for both the contact's server and the user's server. 3.1.5. Server Processing of Outbound Subscription Approval When the contact's client sends the subscription approval, the contact's server MUST stamp the outbound stanza with the bare JID <contact@domain> of the contact and route or deliver the stanza to the user. CS: <presence from='juliet@example.com' to='romeo@example.net' type='subscribed'/> The contact's server then MUST send a roster push to all of the contact's interested resources. CS: <iq to='juliet@example.com/balcony' type='set' id='a78b4q6ha463'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' subscription='from'/> </query> </iq> CS: <iq to='juliet@example.com/chamber' type='set' id='a78b4q6ha464'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' subscription='from'/> </query> </iq> The contact's server MUST then also send current presence information to the user from each of the contact's available resources. Saint-Andre Expires January 18, 2008 [Page 22]
Internet-Draft XMPP IM July 2007 CS: <presence from='juliet@example.com/balcony' to='romeo@example.net'/> CS: <presence from='juliet@example.com/chamber' to='romeo@example.net'/> From the perspective of the contact, there now exists a subscription from the user. In order to subscribe to the user's presence, the contact would then send a subscription request to the user. (XMPP clients will often automatically send the subscription request instead of requiring the contact to initiate the subscription request, since it is assumed that the desired end state is a mutual subscription.) Naturally, when the contact sends a subscription request to the user, the Appendix A (as well as the roles of the two JIDs) will be different from those shown in the foregoing examples. 3.1.6. Server Processing of Inbound Subscription Approval When the user's server receives the subscription approval, it MUST first check if the contact is in the user's roster with a subscription='none' or subscription='from' and the 'ask' flag set to "subscribe" (i.e., a Appendix A of "None + Pending Out" or "From + Pending Out"). 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 foregoing check is successful, the user's server MUST initiate a roster push to all of the user's interested resources, containing an updated roster item for the contact with the 'subscription' attribute set to a value of "to". Saint-Andre Expires January 18, 2008 [Page 23]
Internet-Draft XMPP IM July 2007 US: <iq to='romeo@example.net/foo' type='set' id='b89c5r7ib576'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='to'/> </query> </iq> US: <iq to='romeo@example.net/bar' type='set' id='b89c5r7ib577'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='to'/> </item> </query> </iq> From the perspective of the user, there now exists a subscription to the contact's presence information. The user's server MUST also deliver the available presence stanza received from each of the contact's available resources to each of the user's available resources. US: <presence from='juliet@example.com/balcony' to='romeo@example.net'/> US: <presence from='juliet@example.com/balcony' to='romeo@example.net'/> US: <presence from='juliet@example.com/chamber' to='romeo@example.net'/> US: <presence from='juliet@example.com/chamber' to='romeo@example.net'/> 3.2. Cancelling a Subscription 3.2.1. Client Generation of Subscription Cancellation If a contact would like to cancel a subscription that it has previously granted to a user, it sends a presence stanza of type "unsubscribed". CC: <presence to='romeo@example.net' type='unsubscribed'/> Saint-Andre Expires January 18, 2008 [Page 24]
Internet-Draft XMPP IM July 2007 3.2.2. Server Processing of Outbound Subscription Cancellation As mentioned, the contact's server MUST stamp the outbound subscription cancellation with the bare JID <user@domain> of the contact. CS: <presence from='juliet@example.com' to='romeo@example.net' type='unsubscribed'/> If the user is hosted on the same server, the server MUST adhere to the rules specified in the next section when processing the subscription cancellation. If the user is hosted on a different server, the contact's server then routes the stanza to that foreign domain in accordance with core XMPP stanza processing rules. The contact's server then MUST send a roster push with the updated roster item to all of the contact's interested resources. CS: <iq to='juliet@example.com/balcony' type='set' id='a78b4q6ha465'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' subscription='none'/> </query> </iq> CS: <iq to='juliet@example.com/chamber' type='set' id='a78b4q6ha466'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' subscription='none'/> </query> </iq> 3.2.3. Server Processing of Inbound Subscription Cancellation When the user's server receives the inbound subscription cancellation, it MUST modify the subscription state and send a roster push to the user's interested resource(s). Saint-Andre Expires January 18, 2008 [Page 25]
Internet-Draft XMPP IM July 2007 US: <iq to='romeo@example.net/foo' type='set' id='h37h3u1bv400'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='none'/> </query> </iq> US: <iq to='romeo@example.net/bar' type='set' id='h37h3u1bv401'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='none'/> </item> </query> </iq> 3.3. Unsubscribing 3.3.1. Client Generation of Unsubscribe If a user would like to unsubscribe from a contact's presence, it sends a presence stanza of type "unsubscribe". UC: <presence to='juliet@example.com' type='unsubscribe'/> 3.3.2. Server Processing of Outbound Unsubscribe As mentioned, the user's server MUST stamp the outbound unsubscribe with the bare JID <user@domain> of the user. US: <presence from='romeo@example.net' to='juliet@example.com' type='unsubscribe'/> If the contact is hosted on the same server, the server MUST adhere to the rules specified in the next section when processing the unsubscribe. If the contact is hosted on a different server, the user's server then routes the stanza to that foreign domain in accordance with core XMPP stanza processing rules. The user's server then MUST send a roster push with the updated roster item to all of the user's interested resources. Saint-Andre Expires January 18, 2008 [Page 26]
Internet-Draft XMPP IM July 2007 US: <iq to='romeo@example.net/foo' type='set' id='h37h3u1bv402'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='none'/> </query> </iq> US: <iq to='romeo@example.net/bar' type='set' id='h37h3u1bv403'> <query xmlns='jabber:iq:roster'> <item jid='juliet@example.com' subscription='none'/> </item> </query> </iq> 3.3.3. Server Processing of Inbound Unsubscribe When the contact's server receives the inbound unsubscribe, it MUST modify the subscription state and send a roster push to the contact's interested resource(s). CS: <iq to='juliet@example.com/balcony' type='set' id='a78b4q6ha467'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' subscription='none'/> </query> </iq> CS: <iq to='juliet@example.com/chamber' type='set' id='a78b4q6ha468'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.net' subscription='none'/> </query> </iq> 4. Exchanging Presence Information Saint-Andre Expires January 18, 2008 [Page 27]
Internet-Draft XMPP IM July 2007 4.1. Overview The concept of presence refers to an entity's availability for communication over a network. At the most basic level, presence is a boolean "on/off" variable that signals whether an entity is available or unavailable for communication (the terms "online" and "offline" are also used). In XMPP, a principal's availability is signalled when a client controlled by the principal generates a <presence/> stanza with no 'type' attribute, and an entity's lack of availability is signalled when a client generates a <presence/> stanza whose 'type' attribute has a value of "unavailable". In XMPP-based applications that combine messaging and presence functionality, the default type of communication for which presence signals availability is messaging; however, XMPP-based applications are not required to combine messaging and presence functionality, and can provide standalone presence features without messaging (in addition, XMPP servers do not require presence information in order to successfully route message and IQ stanzas). XMPP presence typically follows a "publish-subscribe" or "observer" pattern, wherein an entity sends presence information to its server, and its server then broadcasts that information to all of the entity's contacts who have a subscription to the entity's presence (in the terminology of [IMP-MODEL], an entity that generates presence information is a "presentity" and the entities that receive presence information are "subscribers"). A client generates presence for broadcasting to all subscribed entities by sending a presence stanza to its server with no 'to' address, where the presence stanza has either no 'type' attribute or a 'type' attribute whose value is "unavailable". This type of presence is called BROADCASTED PRESENCE. (A client MAY also send DIRECTED PRESENCE, i.e., a presence stanza with a 'to' address; this is less common but is sometimes used to send presence to entities that are not subscribed to the principal's presence.) After a client completes the preconditions specified in [XMPP-CORE], it can establish a PRESENCE SESSION at its server by sending initial presence (Section 4.2). Such a presence session is terminated by sending unavailable presence (Section 4.5). Note: A user SHOULD NOT send a presence update to broadcast information that changes independently of the user's presence and availability for communication. 4.2. Initial Presence Saint-Andre Expires January 18, 2008 [Page 28]
Internet-Draft XMPP IM July 2007 4.2.1. Client Generation After completing the preconditions described in [XMPP-CORE] (REQUIRED) and requesting the roster (RECOMMENDED), a client SHOULD signal its availability for communication by sending INITIAL PRESENCE to its server, i.e., a presence stanza with no 'to' address (signalling that it is meant to be broadcasted by the server on behalf of the client) and no 'type' attribute (signalling the user's availability). After sending initial presence, a connected resource (in the terminology of [XMPP-CORE]) is said to be an AVAILABLE RESOURCE. UC: <presence/> 4.2.2. Server Processing of Outbound Presence Upon receiving initial presence from a client, the user's server MUST send the initial presence stanza from the full JID <user@domain/resource> of the user to all contacts that are subscribed to the user's presence information; such contacts are those for which a JID is present in the user's roster with the 'subscription' attribute set to a value of "from" or "both". Note: In the following examples, the "user" is juliet@example.com and the user has three contacts in her roster with a subscription state of from or both: romeo@example.net, mercutio@example.com, and benvolio@example.com. US: <presence from='juliet@example.com/balcony' to='romeo@example.net'/> US: <presence from='juliet@example.com/balcony' to='mercutio@example.com'/> US: <presence from='juliet@example.com/balcony' to='benvolio@example.com'/> The user's server MUST also broadcast initial presence from the user's newly available resource to all of the user's available resources. US: <presence from='juliet@example.com/balcony' to='juliet@example.com/balcony'/> US: <presence from='juliet@example.com/balcony' to='juliet@example.com/chamber'/> In the absence of presence information about the user's contacts, the Saint-Andre Expires January 18, 2008 [Page 29]
Internet-Draft XMPP IM July 2007 user's server SHOULD also send presence probes to the user's contacts on behalf of the user as specified under Section 4.3. 4.2.3. Server Processing of Inbound Presence Upon receiving presence from the user, the contact's server MUST deliver the user's presence stanza to the full JIDs <contact@domain/resource> associated with all of the contact's available resources. CC: <presence from='juliet@example.com/balcony' to='romeo@example.net'/> CC: <presence from='juliet@example.com/balcony' to='romeo@example.net'/> 4.2.4. Client Processing of Inbound Presence When the contact's client receives presence from the user and the user is in the contact's roster, it SHOULD display the presence information in an appropriate roster interface. If the user is not in the contact's roster but the contact and the user are actively exchanging message or IQ stanzas, the contact's client SHOULD display the presence information in the user interface for that chat session. Otherwise, the client SHOULD ignore the presence information and not display it to the contact. 4.3. Presence Probes A PRESENCE PROBE is a presence stanza whose 'type' attribute has a value of "probe". The value of the 'from' address SHOULD be the full JID <user@domain/resource> of the probing user and the value of the 'to' address SHOULD be the bare JID <contact@domain> of the contact whose availability the user wants to discover. US: <presence from='juliet@example.com/balcony' to='romeo@example.net' type='probe'/> A presence probe SHOULD NOT be sent by a client. Instead, it is designed to be sent by a user's server on the user's behalf in order to discover the availability of the user's contacts. Saint-Andre Expires January 18, 2008 [Page 30]
Internet-Draft XMPP IM July 2007 4.3.1. Server Generation of Outbound Presence Probe When a server needs to discover the availability of a user's contact, it SHOULD send a presence probe from the full JID <user@domain/resource> of the user to the bare JID <contact@domain> of the contact. The server SHOULD send a probe to a contact only if the contact is in the user's roster with the 'subscription' attribute set to a value of "to" or "both" (i.e., if the user is subscribed to the contact's presence). The user's server SHOULD send a presence probe whenever the user starts a new presence session by sending initial presence; however, the server MAY choose not to send the probe at that point if it has what it deems to be reliable and up-to-date presence information about the user's contacts (e.g., because the user has another available resource or because the user briefly logged off and on before the new presence session began). US: <presence from='juliet@example.com/balcony' to='romeo@example.net' type='probe'/> US: <presence from='juliet@example.com/balcony' to='benvolio@example.com' type='probe'/> US: <presence from='juliet@example.com/balcony' to='nurse@example.com' type='probe'/> 4.3.2. Server Processing of Inbound Presence Probe Upon receiving a presence probe from the user's server on behalf of the user, the contact's server SHOULD reply as follows: 1. If the contact account does not exist or the user is in the contact's roster with a subscription state other than "From", "From + Pending Out", or "Both" (as defined under Appendix A), the contact's server MUST return a presence stanza of type "unsubscribed" in response to the presence probe (however, if a server receives a presence probe from a configured hostname of the server itself or another such trusted service, it MAY provide presence information about the user to that entity). CS: <presence from='mercutio@example.com' to='juliet@example.com' type='unsubscribed'/> Saint-Andre Expires January 18, 2008 [Page 31]
Internet-Draft XMPP IM July 2007 2. 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. 3. 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 with no 'to' attribute received by the server from each of the contact's available resources. CS: <presence from='romeo@example.net/foo' to='juliet@example.com'/> CS: <presence from='romeo@example.net/bar' to='juliet@example.com'> <show>away</show> </presence> 4.4. Subsequent Presence Broadcast 4.4.1. Client Generation After sending initial presence, the user's client may update its availability for broadcasting at any time during its session by sending a presence stanza with no 'to' address and no 'type' attribute. UC: <presence> <show>away</show> </presence> 4.4.2. Server Processing of Outbound Presence Upon receiving a presence stanza expressing updated availability, the user's server MUST broadcast the full XML of that presence stanza to all contacts who meet both of the following criteria: 1. The contact is in the user's roster with a subscription type of "from" or "both". 2. The last presence stanza received from the contact during the user's presence session was not of type "error", "unavailable", or "unsubscribe". Saint-Andre Expires January 18, 2008 [Page 32]
Internet-Draft XMPP IM July 2007 US: <presence from='juliet@example.com/balcony' to='romeo@example.net'> <show>away</show> </presence> US: <presence from='juliet@example.com/balcony' to='benvolio@example.com'> <show>away</show> </presence> US: <presence from='juliet@example.com/balcony' to='mercutio@example.com'> <show>away</show> </presence> Note: As an optimization, if the subscription state is "both" then the user's server MAY choose to broadcast subsequent presence only if the server has received available presence from the contact at some point during the user's session; i.e., if the server never received available presence from the contact and the user has a mutual presence subscription with the contact, it MAY decline to send subsequent presence to the contact. The user's server MUST also send the presence stanza to all of the user's available resources. US: <presence from='juliet@example.com/balcony' to='juliet@example.com/chamber'> <show>away</show> </presence> US: <presence from='juliet@example.com/balcony' to='juliet@example.com/balcony'> <show>away</show> </presence> 4.4.3. Server Processing of Inbound Presence Upon receiving presence from the user, the contact's server MUST deliver the user's presence stanza to the full JIDs <contact@domain/resource> associated with all of the contact's available resources. Saint-Andre Expires January 18, 2008 [Page 33]
Internet-Draft XMPP IM July 2007 CS: <presence from='juliet@example.com/balcony' to='romeo@example.net'> <show>away</show> </presence> CS: <presence from='juliet@example.com/balcony' to='romeo@example.net'> <show>away</show> </presence> 4.4.4. Client Processing of Inbound Presence When the contact's client receives presence from the user and the user is in the contact's roster, it SHOULD display the presence information in an appropriate roster interface. If the user is not in the contact's roster but the contact and the user are actively exchanging message or IQ stanzas, the contact's client SHOULD display the presence information in the user interface for that chat session. Otherwise, the client SHOULD ignore the presence information and not display it to the contact. 4.5. Unavailable Presence 4.5.1. Client Generation Before ending its presence session with a server, the user's client SHOULD gracefully become unavailable by sending UNAVAILABLE PRESENCE, i.e., a presence stanza that possesses no 'to' attribute and that possesses a 'type' attribute whose value is "unavailable". UC: <presence type='unavailable'/> Optionally, the final presence stanza MAY contain one or more <status/> elements specifying the reason why the user is no longer available. US: <presence type='unavailable'> <status>going on vacation</status> </presence> 4.5.2. Server Processing of Outbound Unavailable Presence The user's server MUST NOT depend on receiving unavailable presence from an available resource, since the resource may become unavailable ungracefully (e.g., the resource may be timed out by the server Saint-Andre Expires January 18, 2008 [Page 34]
Internet-Draft XMPP IM July 2007 because of inactivity). If an available resource becomes unavailable for any reason (either gracefully or ungracefully), the user's server MUST broadcast unavailable presence to all contacts that meet both of the following criteria: 1. The contact is in the user's roster with a subscription type of "from" or "both". 2. The last presence stanza received from the contact during the user's presence session was not of type "error", "unavailable", or "unsubscribe". If the unavailable presence stanza was gracefully received from the client, the server MUST broadcast the full XML of the presence stanza. US: <presence from='juliet@example.com/balcony' to='romeo@example.net' type='unavailable'/> US: <presence from='juliet@example.com/balcony' to='benvolio@example.com' type='unavailable'/> US: <presence from='juliet@example.com/balcony' to='mercutio@example.com' type='unavailable'/> The user's server MUST also send the unavailable presence stanza to all of the user's remaining available resources. US: <presence from='juliet@example.com/balcony' to='juliet@example.com/chamber' type='unavailable'/> Note: Any presence stanza with no 'type' attribute and no 'to' attribute that is sent after sending broadcasted unavailable presence MUST be broadcasted by the server to all subscribers (i.e., MUST be treated as equivalent to "initial presence" for a new presence session). 4.5.3. Server Processing of Inbound Unavailable Presence Upon receiving unavailable presence from the user, the contact's server MUST deliver the user's presence stanza to the full JIDs <contact@domain/resource> associated with all of the contact's available resources. Saint-Andre Expires January 18, 2008 [Page 35]
Internet-Draft XMPP IM July 2007 CS: <presence from='juliet@example.com/balcony' to='romeo@example.net' type='unavailable'/> CS: <presence from='juliet@example.com/balcony' to='romeo@example.net' type='unavailable'/> 4.5.4. Client Processing of Inbound Unavailable Presence When the contact's client receives unavailable presence from the user and the user is in the contact's roster, it SHOULD display the unavailable presence information in an appropriate roster interface. If the user is not in the contact's roster but the contact and the user are actively exchanging message or IQ stanzas, the contact's client SHOULD display the unavailable presence information in the user interface for that chat session. Otherwise, the client SHOULD ignore the unavailable presence information and not display it to the contact. 4.6. Directed Presence This section supplements and in some respects modifies the rules defined above, but only for the special case of directed presence. 4.6.1. Client Generation As noted, directed presence is a presence stanza with a 'to' attribute whose value is the bare JID or full JID of the other entity and with either no 'type' attribute or a 'type' attribute whose value is "unavailable". 4.6.2. Server Processing of Outbound Directed Presence When the user's server receives the directed presence stanza, it SHOULD process it according to the following rules. 1. If the user sends directed available or unavailable 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 broadcasted unavailable presence, the user's server MUST route or deliver the full XML of that presence stanza but SHOULD NOT otherwise modify the contact's status regarding broadcasted presence (i.e., it SHOULD include the contact's JID in any subsequent presence broadcasts initiated by the user). Saint-Andre Expires January 18, 2008 [Page 36]
Internet-Draft XMPP IM July 2007 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 broadcasted unavailable presence, 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 route 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 connected 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. 4.6.3. Server Processing of Inbound Directed Presence From the perspective of the contact's server, there is no difference between broadcasted presence and directed presence, so the contact's server follows the existing rules for processing of inbound presence. 4.6.4. Client Processing of Inbound Directed Presence When the contact's client receives presence from the user and the user is in the contact's roster, it SHOULD display the presence information in an appropriate roster interface. If the user is not in the contact's roster but the contact and the user are actively exchanging message or IQ stanzas, the contact's client SHOULD display the presence information in an appropriate user interface. Otherwise, the client SHOULD ignore the presence information and not display it to the contact. 4.7. Presence Syntax 4.7.1. Values of the Type Attribute The absence of a 'type' attribute signals that the relevant entity is available for communication (see Section 4.2 and Section 4.4). A 'type' attribute with a value of "unavailable" signals that the relevant entity is not available for communication (see Section 4.5). Saint-Andre Expires January 18, 2008 [Page 37]
Internet-Draft XMPP IM July 2007 The XMPP presence stanza is also used to negotiate and manage subscriptions to the presence of other entities. These tasks are completed via presence stanzas of type "subscribe", "unsubscribe", "subscribed", and "unsubscribed" as described under Section 3. If a user and contact are associated with different XMPP servers, those servers also use a special presence stanza of type "probe" in order to determine the availability of the entity on the peer server; for details, see Section 4.3. Clients SHOULD NOT send presence stanzas of type "probe". The values of the 'type' attribute can be summarized as follows: o error -- An error has occurred regarding processing of a previously-sent presence stanza; if the presence stanza is of type "error", it MUST include an <error/> child element (see see [XMPP-CORE]). o probe -- A request for an entity's current presence; SHOULD be generated only by a server on behalf of a user. 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 -- The sender is unsubscribing from another entity's presence. o unsubscribed -- The subscription request has been denied or a previously-granted subscription has been cancelled. o unavailable -- Signals that the entity is no longer available for communication. 4.7.2. Child Elements In accordance with the default namespace declaration, a presence stanza is qualified by the 'jabber:client' or 'jabber:server' namespace, which defines certain allowable children of presence stanzas, in particular the <show/>, <status/>, and <priority/> elements. These child elements are used to provide more detailed information about an entity's availability. Typically these child elements are provided only if the presence stanza possesses no 'type' attribute, although exceptions are noted in the text that follows. 4.7.2.1. Show The OPTIONAL <show/> element specifies the particular availability sub-state of an entity or a specific resource thereof. A presence stanza MUST NOT contain more than one <show/> element. The <show/> element MUST NOT possess any attributes. The XML character data of the <show/> element is not human-readable. The data MUST be one of Saint-Andre Expires January 18, 2008 [Page 38]
Internet-Draft XMPP IM July 2007 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 dnd -- The entity or resource is busy (dnd = "Do Not Disturb"). o xa -- The entity or resource is away for an extended period (xa = "eXtended Away"). If no <show/> element is provided, the entity is assumed to be online and available. <presence> <show>dnd</show> </presence> 4.7.2.2. Status The OPTIONAL <status/> element contains XML character data specifying a natural-language description of an entity's availability. It is normally used in conjunction with the show element to provide a detailed description of an availability state (e.g., "In a meeting") when the presence stanza has no 'type' attribute. <presence from='romeo@example.net/orchard' xml:lang='en'> <show>dnd</show> <status>Wooing Juliet</status> </presence> 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 (either explicitly or by inheritance from the 'xml:lang' value of an element farther up in the XML hierarchy, which may include the XML stream header as described in [XMPP-CORE]). <presence from='romeo@example.net/orchard' xml:lang='en'> <show>dnd</show> <status>Wooing Juliet</status> <status xml:lang='cs'>Dvořím se Julii</status> </presence> A presence stanza of type "unavailable" MAY also include a <status/> element to provide detailed information about why the entity is going offline. Saint-Andre Expires January 18, 2008 [Page 39]
Internet-Draft XMPP IM July 2007 <presence from='romeo@example.net/orchard' type='unavailable'> <status>Busy IRL</status> </presence> The <status/> child MAY also be sent in a subscription-related presence stanza (i.e., type "subscribe", "subscribed", "unsubscribe", or "unsubscribed") to provide a description of the action. The receiving client MAY present this <status/> to a human user (see Section 11). <presence from='romeo@example.net' to='nurse@example.com' type='subscribe'> <status>Hi, Juliet said I should add you to my buddy list.</status> </presence> 4.7.2.3. Priority The OPTIONAL <priority/> element contains non-human-readable XML character data that specifies the priority level of the resource. The value MUST be an integer between -128 and +127. A presence stanza MUST NOT contain more than one <priority/> element. The <priority/> element MUST NOT possess any attributes. <presence xml:lang='en'> <show>dnd</show> <status>Wooing Juliet</status> <status xml:lang='cs'>Dvořím se Julii</status> <priority>1</priority> </presence> If no priority is provided, the processing server or client SHOULD consider the priority to be zero. For information regarding the semantics of priority values in stanza processing within instant messaging and presence applications, refer to Server Rules for Processing XML Stanzas (Section 8). 4.7.2.4. Extended Content As described in [XMPP-CORE], an XML stanza MAY contain any properly- namespaced child element; this applies to the presence stanza as well. Saint-Andre Expires January 18, 2008 [Page 40]
Internet-Draft XMPP IM July 2007 <presence from='romeo@example.net'> <c xmlns='http://jabber.org/protocol/caps' node='http://psi-im.org/caps' ver='0.11'/> </presence> Any extended content included in a presence stanza SHOULD represent aspects of an entity's availability for communication or provide information about communication-related capabilities. 5. Exchanging Messages Once a client has authenticated with a server and bound a resource to an XML stream as described in [XMPP-CORE], an XMPP server will route XML stanzas to and from that client. One type of stanza that may be exchanged is <message/>. 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 Processing XML Stanzas (Section 8), 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). Thus a message stanza is used to "push" information to another entity. 5.1. Attributes 5.1.1. To Attribute 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 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>. <message from='juliet@example.com/balcony' to='romeo@example.net' type='chat' xml:lang='en'> <body>Art thou not Romeo, and a Montague?</body> </message> If the message is being sent in reply to a message previously Saint-Andre Expires January 18, 2008 [Page 41]
Internet-Draft XMPP IM July 2007 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 of the form <user@domain/resource> rather than of the form <user@domain> unless the sender has knowledge (via presence) that the intended recipient's resource is no longer available. <message from='romeo@example.net/orchard' to='juliet@example.com/balcony' type='chat' xml:lang='en'> <body>Neither, fair saint, if either thee dislike.</body> </message> 5.1.2. Type Attribute Common uses of the message stanza 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 other alerts, and errors. These uses are differentiated via the 'type' attribute. Inclusion of the 'type' attribute is RECOMMENDED. 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 receiving client SHOULD present the message in an interface enabling one-to-one chat between the two parties, including an appropriate conversation history. o error -- The message is generated by by an entity that experiences an error in processing a message received from another entity (for details regarding stanza error syntax, see [XMPP-CORE]). A client that receives a message of type "error" 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 (similar to that of [IRC]). A receiving client SHOULD present the message in 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 document (for details, see [XEP-0045]). o headline -- The message is probably generated by an automated service that delivers or broadcasts content (news, sports, market information, syndicated content, alerts, etc.) or the sender wishes the message to be delivered as if it were. No reply to the message is expected, and a receiving client SHOULD present the message in an interface that appropriately differentiates the message from standalone messages, chat sessions, or groupchat Saint-Andre Expires January 18, 2008 [Page 42]
Internet-Draft XMPP IM July 2007 sessions (e.g., by not providing the recipient with the ability to reply). The receiving server SHOULD deliver the message to all of the recipient's available resources. 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 receiving client SHOULD present the message in an interface enabling the recipient to reply, but without a conversation history. This is the default value of the 'type' attribute. 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). Although the 'type' attribute is OPTIONAL, it is considered polite to mirror the type in any replies to a message; furthermore, some specialized applications (e.g., a multi-user chat service) MAY at their discretion enforce the use of a particular message type (e.g., type='groupchat'). 5.2. Child Elements An XMPP message stanza MAY contain any allowable child elements qualified by the 'jabber:client' (or 'jabber:server') namespace, as well as any other properly-namespaced child element that consists of extended content. The defined payloads are described in the following sections and extended content payloads are described in the appropriate XMPP extension specifications (not herein). 5.2.1. Body The <body/> element contains human-readable XML character data that specifies the textual contents of the message; this child element is normally included but is OPTIONAL. <message to='romeo@example.net' from='juliet@example.com/balcony' type='chat' xml:lang='en'> <body>Wherefore art thou, Romeo?</body> </message> 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 in a message stanza, but only if each Saint-Andre Expires January 18, 2008 [Page 43]
Internet-Draft XMPP IM July 2007 instance possesses an 'xml:lang' attribute with a distinct language value (either explicitly or by inheritance from the 'xml:lang' value of an element farther up in the XML hierarchy, which may include the XML stream header as described in [XMPP-CORE]). <message to='romeo@example.net' from='juliet@example.com/balcony' type='chat' xml:lang='en'> <body>Wherefore art thou, Romeo?</body> <body xml:lang='cs'>PročeŽ jsi ty, Romeo?</body> </message> The <body/> element MUST NOT contain mixed content (as defined in Section 3.2.2 of [XML]). 5.2.2. Subject The <subject/> element contains human-readable XML character data that specifies the topic of the message. <message to='romeo@example.net' from='juliet@example.com/balcony' type='chat' xml:lang='en'> <subject>I implore you!</subject> <body>Wherefore art thou, Romeo?</body> </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 (either explicitly or by inheritance from the 'xml:lang' value of an element farther up in the XML hierarchy, which may include the XML stream header as described in [XMPP-CORE]). Saint-Andre Expires January 18, 2008 [Page 44]
Internet-Draft XMPP IM July 2007 <message to='romeo@example.net' from='juliet@example.com/balcony' type='chat' xml:lang='en'> <subject>I implore you!</subject> <subject xml:lang='cs'> Úpěnlivě prosím! </subject> <body>Wherefore art thou, Romeo?</body> <body xml:lang='cs'>Pročež jsi ty, Romeo?</body> </message> The <subject/> element MUST NOT contain mixed content (as defined in Section 3.2.2 of [XML]). 5.2.3. Thread The primary use of the XMPP <thread/> element is to uniquely identify a conversation thread or "chat session" between two entities instantiated by <message/> stanzas of type 'chat'. However, the XMPP <thread/> element may also be used to uniquely identify an analogous thread between two entities instantiated by <message/> stanzas of type 'headline' or 'normal', or among multiple entities in the context of a multi-user chat room instantiated by <message/> stanzas of type 'groupchat'. It may also be used for <message/> stanzas not related to a conversation, such as a game session or between plugins. The value of the <thread/> element MUST be a universally unique identifier (UUID) as described in [UUID]. The use of the <thread/> element is OPTIONAL. The <thread/> element 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]). 5.3. Extended Content As described in [XMPP-CORE], an XML stanza MAY contain any properly- namespaced child element; this applies to the message stanza as well. Saint-Andre Expires January 18, 2008 [Page 45]
Internet-Draft XMPP IM July 2007 <message to='romeo@example.net' from='juliet@example.com/balcony' type='chat' xml:lang='en'> <body>Wherefore art thou, Romeo?</body> <html xmlns='http://jabber.org/protocol/xhtml-im'> <body xmlns='http://www.w3.org/1999/xhtml'> Wherefore <span style='font-style: italic'>art</span> thou, <span style='color:red'>Romeo</span>? </body> </html> </message> 6. Exchanging IQ Stanzas As described in [XMPP-CORE], IQ stanzas provide a structured request- response mechanism. The basic semantics of that mechanism (e.g., that the 'id' attribute is required) are defined in [XMPP-CORE], whereas the specific semantics required to complete particular use cases are defined in all cases by the extended namespace that qualifies the direct child element of an IQ stanza of type "get" or "set". The 'jabber:client' and 'jabber:server' namespaces do not define any children of IQ stanzas other than the <error/> common to all stanza types. This document defines one such extended namespace, for Managing the Roster (Section 2). However, an IQ stanza MAY contain structured information qualified by any extended namespace. 7. A Sample Session The examples in this section illustrate a possible instant messaging and presence session. 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 identifier is "chamber" and another whose resource identifier is "balcony") o benvolio@example.org (subscription="to") o mercutio@example.org (subscription="from") First, the user completes the preconditions (stream establishment, TLS and SASL negotiation, and resource binding) described in [XMPP-CORE]; those packet flows are not reproduced here. Next, the user requests his roster: Saint-Andre Expires January 18, 2008 [Page 46]
Internet-Draft XMPP IM July 2007 Example 1: User requests current roster from server: UC: <iq from='romeo@example.net/balcony' type='get' id='ex1'> <query xmlns='jabber:iq:roster'/> </iq> Example 2: User receives roster from server: US: <iq to='romeo@example.net/balcony' type='result' id='ex1'> <query xmlns='jabber:iq:roster'> <item jid='romeo@example.com' name='Juliet' subscription='both'> <group>Friends</group> </item> <item jid='benvolio@example.org' name='Benvolio' subscription='to'/> <item jid='mercutio@example.org' name='Mercutio' subscription='from'/> </query> </iq> Now the user begins a presence session. Example 3: User sends initial presence: UC: <presence from='romeo@example.net/orchard'/> Example 4: User's server sends presence probes to contacts with subscription="to" and subscription="both" on behalf of the user's available resource: US: <presence type='probe' from='romeo@example.net/orchard' to='juliet@example.com'/> US: <presence type='probe' from='romeo@example.net/orchard' to='benvolio@example.org'/> Saint-Andre Expires January 18, 2008 [Page 47]
Internet-Draft XMPP IM July 2007 Example 5: User's server sends initial presence to contacts with subscription="from" and subscription="both" on behalf of the user's available resource: US: <presence from='romeo@example.net/orchard' to='juliet@example.com'/> US: <presence from='romeo@example.net/orchard' to='mercutio@example.org'/> Example 6: Contacts' servers reply to presence probe on behalf of all available resources: CS: <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> CS: <presence from='juliet@example.com/chamber' to='romeo@example.net/orchard'> <priority>1</priority> </presence> CS: <presence from='benvolio@example.org/pda' to='romeo@example.net/orchard' xml:lang='en'> <show>dnd</show> <status>gallivanting</status> </presence> Saint-Andre Expires January 18, 2008 [Page 48]
Internet-Draft XMPP IM July 2007 Example 7: Contacts' servers deliver user's initial presence to all available resources or return unsubscribed to user: CS: <presence from='romeo@example.net/orchard' to='juliet@example.com'/> CS: <presence from='romeo@example.net/orchard' to='juliet@example.com'/> CS: <presence from='mercutio@example.org' to='romeo@example.net' type='unsubscribed'/> Example 8: User sends directed presence to another user not in his roster: UC: <presence from='romeo@example.net/orchard' to='nurse@example.com' xml:lang='en'> <show>dnd</show> <status>courting Juliet</status> <priority>0</priority> </presence> Now the user has a threaded conversation (chat session) with one of his contacts. Saint-Andre Expires January 18, 2008 [Page 49]
Internet-Draft XMPP IM July 2007 Example 9: A threaded conversation CC: <message from='juliet@example.com/balcony' to='romeo@example.net' type='chat' xml:lang='en'> <body>Art thou not Romeo, and a Montague?</body> <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread> </message> UC: <message from='romeo@example.net/orchard' to='juliet@example.com/balcony' type='chat' xml:lang='en'> <body>Neither, fair saint, if either thee dislike.</body> <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread> </message> CC: <message from='juliet@example.com/balcony' to='romeo@example.net/orchard' type='chat' xml:lang='en'> <body>How cam'st thou hither, tell me, and wherefore?</body> <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread> </message> And so on. The user can also send subsequent broadcasted presence. Example 10: User sends updated available presence information for broadcasting: UC: <presence xml:lang='en'> <show>away</show> <status>I shall return!</status> <priority>1</priority> </presence> Saint-Andre Expires January 18, 2008 [Page 50]
Internet-Draft XMPP IM July 2007 Example 11: User's server broadcasts updated presence information only to one contact: US: <presence from='romeo@example.net/orchard' to='juliet@example.com' xml:lang='en'> <show>away</show> <status>I shall return!</status> <priority>1</priority> </presence> Example 12: Contact's server delivers updated presence information to all of the contact's available resources ("balcony" and "chamber"): CS: <presence from='romeo@example.net/orchard' to='juliet@example.com' xml:lang='en'> <show>away</show> <status>I shall return!</status> <priority>1</priority> </presence> CS: <presence from='romeo@example.net/orchard' to='juliet@example.com' xml:lang='en'> <show>away</show> <status>I shall return!</status> <priority>1</priority> </presence> Example 13: One of the contact's resources broadcasts final presence: CC: <presence from='juliet@example.com/chamber' type='unavailable'/> Example 14: Contact's server sends unavailable presence information to user: CS: <presence type='unavailable' from='juliet@example.com/chamber' to='romeo@example.net'/> Saint-Andre Expires January 18, 2008 [Page 51]
Internet-Draft XMPP IM July 2007 Example 15: User sends unavailable presence: UC: <presence from='romeo@example.net/orchard' type='unavailable' xml:lang='en'> <status>gone home</status> </presence> Example 16: User's server broadcasts unavailable presence information to contact as well as to the person to whom the user sent directed presence: US: <presence type='unavailable' from='romeo@example.net/orchard' to='juliet@example.com' xml:lang='en'> <status>gone home</status> </presence> US: <presence type='unavailable' from='romeo@example.net/orchard' to='nurse@example.com' xml:lang='en'> <status>gone home</status> </presence> Now the user closes his stream: UC: </stream:stream> And the user's server closes its stream as well: US: </stream:stream> THE END 8. Server Rules for Processing XML Stanzas Basic routing and delivery rules for servers are defined in [XMPP-CORE]. This section defines supplementary rules for XMPP instant messaging and presence servers; in the absence of a supplementary rule defined below (e.g., for stanzas without a 'to' address), the rule defined in [XMPP-CORE] shall apply. Saint-Andre Expires January 18, 2008 [Page 52]
Internet-Draft XMPP IM July 2007 8.1. No Such User If the user account does not exist, how the stanza shall be processed depends on the stanza type. o For a message stanza, the server SHOULD return a <service- unavailable/> stanza error to the sender. o For a presence stanza with no 'type' attribute or a 'type' attribute of "unavailable", the server SHOULD silently ignore the stanza (i.e., not return an error or a presence stanza of type "unsubscribed". o For a presence stanza with of type "subscribe", "subscribed", "unsubscribe", or "unsubscribed", the server MUST follow the guidelines provided under Section 3. o For an IQ stanza, the server MUST return a <service-unavailable/> stanza error to the sender. 8.2. Full JID at Local Domain If the hostname of the domain identifier portion of the JID contained in the 'to' attribute of an inbound stanza matches one of the configured hostnames of the server itself and the JID contained in the 'to' attribute is of the form <user@domain/resource>, the server MUST adhere to the following rules. 8.2.1. Available Resource Matches If an available resource exactly matches the full JID, the recipient's server MUST deliver the stanza to that resource. 8.2.2. No Available Resource Matches If no connected or available resource exactly matches the full JID, how the stanza shall be processed depends on the stanza type. o For a message, the server SHOULD treat the stanza as if it were addressed to <user@domain> as described in the next section. o For a presence stanza, the server SHOULD silently ignore the stanza (i.e., neither deliver it nor return an error or a presence stanza of type "unsubscribe" or "unsubscribed"). o For an IQ stanza, the server MUST return a <service-unavailable/> stanza error to the sender. 8.3. Bare JID at Local Domain If the hostname of the domain identifier portion of the JID contained in the 'to' attribute of an inbound stanza matches one of the configured hostnames of the server itself and the JID contained in Saint-Andre Expires January 18, 2008 [Page 53]
Internet-Draft XMPP IM July 2007 the 'to' attribute is of the form <user@domain>, the server MUST adhere to the following rules. 8.3.1. Available Resources If there is at least one available resource, how the stanza shall be processed depends on the stanza type. 8.3.1.1. Message For a message stanza of type "headline", the server SHOULD deliver the stanza to all available resources. For a message stanza of type "chat", "error", "groupchat", or "normal", the server SHOULD deliver the stanza to the highest- priority available resource. If two or more available resources have the same priority, the server MAY use some other rule (e.g., most recent connect time, most recent activity time, or highest availability as determined by some hierarchy of <show/> values) to choose between them or MAY deliver the message to all such resources. However, for any message type the server MUST NOT deliver the stanza to any available resource with a negative priority; if the only available resource has a negative priority, the server SHOULD handle the message as if there were no available resources as described under Section 8.3.2. In all cases, the server MUST NOT rewrite the 'to' attribute (i.e., it MUST leave it as <user@domain> rather than change it to <user@domain/resource>). 8.3.1.2. Presence For a presence stanza of type "probe", the server MUST handle it directly as described under Section 4.3. For a presence stanza with no type or of type "unavailable", the server MUST deliver the stanza to all available resources. For a presence stanza of type "subscribe", "subscribed", "unsubscribe", or "unsubscribed", the server MUST adhere to the rules defined under Section 3 and summarized under Appendix A. In all cases, the server MUST NOT rewrite the 'to' attribute (i.e., it MUST leave it as <user@domain> rather than change it to <user@domain/resource>). Saint-Andre Expires January 18, 2008 [Page 54]
Internet-Draft XMPP IM July 2007 8.3.1.3. IQ For an IQ stanza, the server itself MUST reply on behalf of the user with either an IQ result or an IQ error, and MUST NOT deliver the IQ stanza to any of the user's available resources. Specifically, if the semantics of the qualifying namespace define a reply that the server can provide on behalf of the user, the server MUST reply to the stanza on behalf of the user by returning either an IQ stanza of type "result" or an IQ stanza of type "error" that is appropriate to the original payload; if not, the server MUST reply with a <service- unavailable/> stanza error. 8.3.2. No Available Resources If there are no available resources associated with the user, how the stanza shall be processed depends on the stanza type. 8.3.2.1. Message For a message stanza, the server MAY choose to store the stanza on behalf of the user and deliver it when the user next becomes available, or forward the message to the user via some other means (e.g., to the user's email account). However, if offline message storage or message forwarding is not enabled, the server MUST return to the sender a <service-unavailable/> stanza error. (Note: Offline message storage and message forwarding are not defined in XMPP, since they are strictly a matter of implementation and service provisioning.) 8.3.2.2. Presence For a presence stanza with no type or of type "unavailable" or "probe", the server SHOULD silently ignore the stanza by not storing it for later delivery or replying to it on behalf of the user. For a presence stanza of type "subscribe", "subscribed", "unsubscribe", or "unsubscribed", the server MUST adhere to the rules defined under Section 3 and summarized under Appendix A. 8.3.2.3. IQ For an IQ stanza, the server itself MUST reply on behalf of the user with either an IQ result or an IQ error, and MUST NOT deliver the IQ stanza to the available resources. Specifically, if the semantics of the qualifying namespace define a reply that the server can provide on behalf of the user, the server MUST reply to the stanza on behalf of the user by returning either an IQ stanza of type "result" or an IQ stanza of type "error" that is appropriate to the original Saint-Andre Expires January 18, 2008 [Page 55]
Internet-Draft XMPP IM July 2007 payload; if not, the server MUST reply with a <service-unavailable/> stanza error. 8.4. Foreign Domain If the hostname of the domain identifier portion of the address contained in the 'to' attribute of an outbound stanza does not match a configured hostname of the server itself, the server MUST attempt to route the stanza to the foreign domain. If there exists an active stream between the two peers, the server shall route the stanza over that stream for processing by the peer server. If not, the server MUST do the following. First, resolve the hostname of the foreign domain (or used a cached resolution of the foreign domain to an IP address). The recommended order of attempted resolutions is as follows: 1. Attempt to resolve the foreign hostname using a DNS [SRV] Service of "xmpp-server" and Proto of "tcp", resulting in resource records such as "_xmpp-server._tcp.example.com.", as specified in [XMPP-CORE]. 2. If the "xmpp-server" address record resolution fails, attempt to resolve the "_im" or "_pres" [SRV] Service as specified in [IMP-SRV], using the "_im" Service for <message/> stanzas and the "_pres" Service for <presence/> stanzas (it is up to the implementation how to handle <iq/> stanzas). This will result in one or more resolutions of the form "_im.<proto>.example.com." or "_pres.<proto>.example.com.", where "<proto>" would be a label registered in the Instant Messaging SRV Protocol Label registry or the Presence SRV Protocol Label registry: either "_xmpp" for an XMPP-aware domain or some other IANA-registered label (e.g., "_simple") for a non-XMPP-aware domain. 3. If both SRV address record resolutions fail, attempt to perform a normal IPv4/IPv6 address record resolution to determine the IP address using the "xmpp-server" port of 5269 registered with the IANA, as specified in [XMPP-CORE]. Note: Administrators of server deployments are strongly encouraged to keep the _im._xmpp, _pres._xmpp, and _xmpp._tcp SRV records properly synchronized, since different implementations might perform the "_im" and "_pres" lookups before the "xmpp-server" lookup. If the foreign domain cannot be resolved, the server SHOULD return a <remote-server- not-found/> stanza error. Second, negotiate XML streams with the foreign domain by following the process defined in [XMPP-CORE]. If the server cannot establish streams with the foreign domain, it SHOULD return a <remote-server- timeout/> stanza error. Saint-Andre Expires January 18, 2008 [Page 56]
Internet-Draft XMPP IM July 2007 Third, route the stanza to the foreign domain for processing by the peer server. 9. IM and Presence Compliance Requirements This section summarizes the specific aspects of the Extensible Messaging and Presence Protocol that MUST be supported by instant messaging and presence servers and clients in order to be considered compliant implementations. All such applications MUST comply with the requirements specified in [XMPP-CORE]. The text in this section specifies additional compliance requirements for instant messaging and presence servers and clients (the requirements described here supplement but do not supersede the core requirements). Note: A server or client MAY support only presence or instant messaging, and is not required to support both if only a presence service or an instant messaging service is desired. 9.1. Servers In addition to core server compliance requirements, an instant messaging and presence server MUST additionally support all server- related instant messaging and presence syntax and semantics defined in this document, including: o Presence broadcast on behalf of clients as specified under Section 4 o Presence subscriptions as specified under Section 3 o Roster storage and management as specified under Section 2 o IM-specific routing and delivery rules as specified under Section 8 9.2. Clients In addition to core client compliance requirements, an instant messaging and presence client MUST additionally support the following protocols: o Generation and processing of the IM-specific semantics of XML stanzas as defined by the XML schemas, including the 'type' attribute of message and presence stanzas as well as their child elements (see Section 5 and Section 4) o All client-related instant messaging syntax and semantics defined in this document, including presence subscriptions and roster management (see Section 3 and Section 2) Saint-Andre Expires January 18, 2008 [Page 57]
Internet-Draft XMPP IM July 2007 o End-to-end object signing and encryption as defined in [XMPP-E2E] A client MUST also handle addresses that are encoded as "im:" URIs as specified in [CPIM], and MAY do so by removing the "im:" scheme and entrusting address resolution to the server as specified under Section 8.4. 10. Internationalization Considerations For internationalization considerations, refer to the relevant section of [XMPP-CORE]. 11. Security Considerations Core security considerations for XMPP are defined in the relevant section of [XMPP-CORE]. Additional considerations that apply only to instant messaging and presence applications of XMPP are defined in several places within this document; specifically: o When a server processes an inbound presence stanza of type "probe" whose intended recipient is a user associated with one of the server's hostnames, the server MUST NOT reveal the user's presence information if the sender is an entity that is not authorized to receive that information as determined by presence subscriptions (see Exchanging Presence Information (Section 4)). o A user's server MUST NOT leak the user's network availability to entities who are not authorized to know the user's presence, either via an explicit subscription as described herein or via an existing trust relationship (such as presence-enabled user directories within organizations). o When a server processes an outbound presence stanza with no type or of type "unavailable", it MUST follow the rules defined under Exchanging Presence Information (Section 4) in order to ensure that such presence information is not broadcasted to entities that are not authorized to know such information. o When a server generates an error stanza in response to receiving a stanza for a user who does not exist, the use of the <service- unavailable/> error condition helps protect against well-known dictionary attacks, since this is the same error condition that is returned if, for instance, the namespace of an IQ child element is not understood, or if offline message storage or message forwarding is not enabled for a domain. Saint-Andre Expires January 18, 2008 [Page 58]
Internet-Draft XMPP IM July 2007 o A client MAY ignore the <status/> element when contained in a presence stanza of type "subscribe", "unsubscribe", "subscribed", or "unsubscribed" in order to help prevent "presence subscription spam". 12. IANA Considerations The following sections update the registrations provided in [RFC3921]. For a number of related IANA considerations, refer to the relevant section of [XMPP-CORE]. 12.1. Instant Messaging SRV Protocol Label Registration Address Resolution for Instant Messaging and Presence [IMP-SRV] defines an Instant Messaging SRV Protocol Label registry for protocols that can provide services that conform to the "_im" SRV Service label. Because XMPP is one such protocol, the IANA registers the "_xmpp" protocol label in the appropriate registry, as follows: Protocol label: _xmpp Specification: XXXX Description: Instant messaging protocol label for the Extensible Messaging and Presence Protocol (XMPP) as defined by XXXX. Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> 12.2. Presence SRV Protocol Label Registration Address Resolution for Instant Messaging and Presence [IMP-SRV] defines a Presence SRV Protocol Label registry for protocols that can provide services that conform to the "_pres" SRV Service label. Because XMPP is one such protocol, the IANA registers the "_xmpp" protocol label in the appropriate registry, as follows: Protocol label: _xmpp Specification: XXXX Description: Presence protocol label for the Extensible Messaging and Presence Protocol (XMPP) as defined by XXXX. Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> 13. References Saint-Andre Expires January 18, 2008 [Page 59]
Internet-Draft XMPP IM July 2007 13.1. Normative References [IMP-REQS] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging / Presence Protocol Requirements", RFC 2779, February 2000. [IMP-SRV] Peterson, J., "Address Resolution for Instant Messaging and Presence", RFC 3861, August 2004. [SRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000. [TERMS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [UUID] Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, July 2005. [XML] Paoli, J., Maler, E., Sperberg-McQueen, C., Yergeau, F., and T. Bray, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", World Wide Web Consortium Recommendation REC- xml-20060816, August 2006, <http://www.w3.org/TR/2006/REC-xml-20060816>. [XML-NAMES] Bray, T., Hollander, D., and A. Layman, "Namespaces in XML", W3C REC-xml-names, January 1999, <http://www.w3.org/TR/REC-xml-names>. [XMPP-CORE] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", draft-saintandre-rfc3920bis-03 (work in progress), July 2007. [XMPP-E2E] Saint-Andre, P., "End-to-End Signing and Object Encryption for the Extensible Messaging and Presence Protocol (XMPP)", RFC 3923, October 2004. 13.2. Informative References [CPIM] Peterson, J., "Common Profile for Instant Messaging (CPIM)", RFC 3860, August 2004. [IMP-MODEL] Saint-Andre Expires January 18, 2008 [Page 60]
Internet-Draft XMPP IM July 2007 Day, M., Rosenberg, J., and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [IRC] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810, April 2000. [RFC3921] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence", RFC 3921, October 2004. [SASL] Melnikov, A. and K. Zeilenga, "Simple Authentication and Security Layer (SASL)", RFC 4422, June 2006. [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. [XEP-0016] Millard, P. and P. Saint-Andre, "Privacy Lists", XSF XEP 0016, February 2007. [XEP-0045] Saint-Andre, P., "Multi-User Chat", XSF XEP 0045, April 2007. [XEP-0054] Saint-Andre, P., "vcard-temp", XSF XEP 0054, March 2003. [XML-SCHEMA] Thompson, H., Maloney, M., Mendelsohn, N., and D. Beech, "XML Schema Part 1: Structures Second Edition", World Wide Web Consortium Recommendation REC-xmlschema-1-20041028, October 2004, <http://www.w3.org/TR/2004/REC-xmlschema-1-20041028>. [VCARD] Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC 2426, September 1998. Appendix A. Subscription States This section provides detailed information about subscription states and server processing of subscription-related presence stanzas (i.e., presence stanzas of type "subscribe", "subscribed", "unsubscribe", and "unsubscribed"). Saint-Andre Expires January 18, 2008 [Page 61]
Internet-Draft XMPP IM July 2007 A.1. Defined States There are four primary subscription states: o None -- the user does not have a subscription to the contact's presence information, and the contact does not have a subscription to the user's presence information o To -- the user has a subscription to the contact's presence information, but the contact does not have a subscription to the user's presence information o From -- the contact has a subscription to the user's presence information, but the user does not have a subscription to the contact's presence information o Both -- both the user and the contact have subscriptions to each other's presence information (i.e., the union of 'from' and 'to') These states are supplemented by various pending sub-states to yield nine possible subscription states: 1. "None" = contact and user are not subscribed to each other, and neither has requested a subscription from the other; this is reflected in the roster by subscription='none' 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; this is reflected in the roster by subscription='none' and ask='subscribe' 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 user has approved subscription request from contact); this is reflected in the roster by subscription='none' 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; this is reflected in the roster by subscription='none' and ask='subscribe' 5. "To" = user is subscribed to contact (one-way); this is reflected in the roster by subscription='to' 6. "To + Pending In" = user is subscribed to contact, and contact has sent user a subscription request but user has not replied yet; this is reflected in the roster by subscription='to' 7. "From" = contact is subscribed to user (one-way); this is reflected in the roster by subscription='from' 8. "From + Pending Out" = contact is subscribed to user, and user has sent contact a subscription request but contact has not replied yet; this is reflected in the roster by subscription='none' and ask='subscribe' Saint-Andre Expires January 18, 2008 [Page 62]
Internet-Draft XMPP IM July 2007 9. "Both" = user and contact are subscribed to each other (two-way); this is reflected in the roster by subscription='both' A.2. Server Processing of Outbound Presence Subscription Stanzas Outbound presence subscription stanzas enable the user to manage his or her subscription to the contact's presence information (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). The following rules apply to outbound routing of the stanza as well as changes to the user's roster. Note: In the following tables, "S.N." stand for SHOULD NOT. A.2.1. Subscribe Table 1: Processing of outbound "subscribe" stanzas +----------------------------------------------------------------+ | EXISTING STATE | ROUTE? | NEW STATE | +----------------------------------------------------------------+ | "None" | MUST | "None + Pending Out" | | "None + Pending Out" | MUST | no state change | | "None + Pending In" | MUST | "None + Pending Out+In" | | "None + Pending Out+In" | MUST | no state change | | "To" | MUST | no state change | | "To + Pending In" | MUST | no state change | | "From" | MUST | "From + Pending Out" | | "From + Pending Out" | MUST | no state change | | "Both" | MUST | no state change | +----------------------------------------------------------------+ Saint-Andre Expires January 18, 2008 [Page 63]
Internet-Draft XMPP IM July 2007 A.2.2. Unsubscribe Table 2: Processing of outbound "unsubscribe" stanzas +----------------------------------------------------------------+ | EXISTING STATE | ROUTE? | NEW STATE | +----------------------------------------------------------------+ | "None" | MUST | no state change | | "None + Pending Out" | MUST | "None" | | "None + Pending In" | MUST | no state change | | "None + Pending Out+In" | MUST | "None + Pending In" | | "To" | MUST | "None" | | "To + Pending In" | MUST | "Pending In" | | "From" | MUST | no state change | | "From + Pending Out" | MUST | "From" | | "Both" | MUST | "From" | +----------------------------------------------------------------+ A.2.3. Subscribed Table 3: Processing of outbound "subscribed" stanzas +----------------------------------------------------------------+ | EXISTING STATE | ROUTE? | NEW STATE | +----------------------------------------------------------------+ | "None" | S.N. | no state change | | "None + Pending Out" | S.N. | no state change | | "None + Pending In" | MUST | "From" | | "None + Pending Out+In" | MUST | "From + Pending Out" | | "To" | S.N. | no state change | | "To + Pending In" | MUST | "Both" | | "From" | S.N. | no state change | | "From + Pending Out" | S.N. | no state change | | "Both" | S.N. | no state change | +----------------------------------------------------------------+ Saint-Andre Expires January 18, 2008 [Page 64]
Internet-Draft XMPP IM July 2007 A.2.4. Unsubscribed Table 4: Processing of outbound "unsubscribed" stanzas +----------------------------------------------------------------+ | EXISTING STATE | ROUTE? | NEW STATE | +----------------------------------------------------------------+ | "None" | S.N. | no state change | | "None + Pending Out" | S.N. | no state change | | "None + Pending In" | MUST | "None" | | "None + Pending Out+In" | MUST | "None + Pending Out" | | "To" | S.N. | no state change | | "To + Pending In" | MUST | "To" | | "From" | MUST | "None" | | "From + Pending Out" | MUST | "None + Pending Out" | | "Both" | MUST | "To" | +----------------------------------------------------------------+ A.3. Server Processing 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 contact to manage the user's access to the contact's presence information (via the "subscribed" and "unsubscribed" types). The following rules apply to delivery of the inbound stanza as well as changes to the contact's roster. Note: In the following tables, "S.N." stand for SHOULD NOT. Saint-Andre Expires January 18, 2008 [Page 65]
Internet-Draft XMPP IM July 2007 A.3.1. Subscribe Table 5: Processing of inbound "subscribe" stanzas +------------------------------------------------------------------+ | EXISTING STATE | DELIVER? | NEW STATE | +------------------------------------------------------------------+ | "None" | MUST | "None + Pending In" | | "None + Pending Out" | MUST | "None + Pending Out+In" | | "None + Pending In" | S.N. | no state change | | "None + Pending Out+In" | S.N. | no state change | | "To" | MUST | "To + Pending In" | | "To + Pending In" | S.N. | no state change | | "From" | S.N. * | no state change | | "From + Pending Out" | S.N. * | no state change | | "Both" | S.N. * | no state change | +------------------------------------------------------------------+ * Server SHOULD auto-reply with "subscribed" stanza A.3.2. Unsubscribe 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 MUST change the state and SHOULD auto-reply by sending a presence stanza of type "unsubscribed" to the contact on behalf of the user. Otherwise the user's server MUST NOT change the state and SHOULD NOT deliver the stanza. These rules are summarized in the following table. Table 6: Processing of inbound "unsubscribe" stanzas +------------------------------------------------------------------+ | EXISTING STATE | DELIVER? | NEW STATE | +------------------------------------------------------------------+ | "None" | S.N. | no state change | | "None + Pending Out" | S.N. | no state change | | "None + Pending In" | S.N. * | "None" | | "None + Pending Out+In" | S.N. * | "None + Pending Out" | | "To" | S.N. | no state change | | "To + Pending In" | S.N. * | "To" | | "From" | S.N. * | "None" | | "From + Pending Out" | S.N. * | "None + Pending Out | | "Both" | S.N. * | "To" | +------------------------------------------------------------------+ * Server SHOULD auto-reply with "unsubscribed" stanza Saint-Andre Expires January 18, 2008 [Page 66]
Internet-Draft XMPP IM July 2007 A.3.3. Subscribed When the user's server receives a presence stanza of type "subscribed" for the user from the contact, if there is no pending outbound request for access to the contact's presence information, then it MUST NOT change the subscription state and SHOULD NOT deliver the stanza to the user. 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, then the user's server MUST change the subscription state but SHOULD NOT deliver the stanza to the user. 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 MUST NOT change the subscription state and SHOULD NOT deliver the stanza to the user. These rules are summarized in the following table. Table 7: Processing of inbound "subscribed" stanzas +------------------------------------------------------------------+ | EXISTING STATE | DELIVER? | NEW STATE | +------------------------------------------------------------------+ | "None" | S.N. | no state change | | "None + Pending Out" | S.N. | "To" | | "None + Pending In" | S.N. | no state change | | "None + Pending Out+In" | S.N. | "To + Pending In" | | "To" | S.N. | no state change | | "To + Pending In" | S.N. | no state change | | "From" | S.N. | no state change | | "From + Pending Out" | S.N. | "Both" | | "Both" | S.N. | no state change | +------------------------------------------------------------------+ A.3.4. Unsubscribed When the user's server receives a presence stanza of type "unsubscribed" for the user from the contact, 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, then the user's server MUST change the subscription state but SHOULD NOT deliver the stanza to the user. Otherwise, the user's server MUST NOT change the subscription state and SHOULD NOT deliver the stanza. These rules are summarized in the following table. Saint-Andre Expires January 18, 2008 [Page 67]
Internet-Draft XMPP IM July 2007 Table 8: Processing of inbound "unsubscribed" stanzas +------------------------------------------------------------------+ | EXISTING STATE | DELIVER? | NEW STATE | +------------------------------------------------------------------+ | "None" | S.N. | no state change | | "None + Pending Out" | S.N. | "None" | | "None + Pending In" | S.N. | no state change | | "None + Pending Out+In" | S.N. | "None + Pending In" | | "To" | S.N. | "None" | | "To + Pending In" | S.N. | "None + Pending In" | | "From" | S.N. | no state change | | "From + Pending Out" | S.N. | "From" | | "Both" | S.N. | "From" | +------------------------------------------------------------------+ Appendix B. Blocking Communication Sections 2.3.5 and 5.4.10 of [IMP-REQS] require that a compliant instant messaging and presence technology must enable a user to block communications from selected users. A protocol for doing so is specified in [XEP-0016]. Appendix C. vCards Sections 3.1.3 and 4.1.4 of [IMP-REQS] require that it be possible to retrieve out-of-band contact information for other users (e.g., telephone number or email address). An XML representation of the vCard specification defined in RFC 2426 [VCARD] is in common use within the Jabber community to provide such information but is out of scope for XMPP (documentation of this protocol is contained in [XEP-0054]). Appendix D. XML Schemas Because validation of XML streams and stanzas is optional, the following XML schemas are provided for descriptive purposes only. These schemas are not normative. The following schemas formally define various XML namespaces used in the core XMPP protocols, in conformance with [XML-SCHEMA]. For schemas defining namespaces for XML streams and other core aspects of XMPP, refer to [XMPP-CORE]. D.1. jabber:client Saint-Andre Expires January 18, 2008 [Page 68]
Internet-Draft XMPP IM July 2007 <?xml version='1.0' encoding='UTF-8'?> <xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema' targetNamespace='jabber:client' xmlns='jabber:client' elementFormDefault='qualified'> <xs:import namespace='urn:ietf:params:xml:ns:xmpp-stanzas'/> <xs:element name='message'> <xs:complexType> <xs:sequence> <xs:choice minOccurs='0' maxOccurs='unbounded'> <xs:element ref='subject'/> <xs:element ref='body'/> <xs:element ref='thread'/> </xs:choice> <xs:any namespace='##other' minOccurs='0' maxOccurs='unbounded'/> <xs:element ref='error' minOccurs='0'/> </xs:sequence> <xs:attribute name='from' type='xs:string' use='optional'/> <xs:attribute name='id' type='xs:NMTOKEN' use='optional'/> <xs:attribute name='to' type='xs:string' use='optional'/> <xs:attribute name='type' use='optional' default='normal'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='chat'/> <xs:enumeration value='error'/> <xs:enumeration value='groupchat'/> <xs:enumeration value='headline'/> <xs:enumeration value='normal'/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute ref='xml:lang' use='optional'/> </xs:complexType> </xs:element> Saint-Andre Expires January 18, 2008 [Page 69]
Internet-Draft XMPP IM July 2007 <xs:element name='body'> <xs:complexType> <xs:simpleContent> <xs:extension base='xs:string'> <xs:attribute ref='xml:lang' use='optional'/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> <xs:element name='subject'> <xs:complexType> <xs:simpleContent> <xs:extension base='xs:string'> <xs:attribute ref='xml:lang' use='optional'/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> <xs:element name='thread' type='xs:NMTOKEN'/> <xs:element name='presence'> <xs:complexType> <xs:sequence> <xs:choice minOccurs='0' maxOccurs='unbounded'> <xs:element ref='show'/> <xs:element ref='status'/> <xs:element ref='priority'/> </xs:choice> <xs:any namespace='##other' minOccurs='0' maxOccurs='unbounded'/> <xs:element ref='error' minOccurs='0'/> </xs:sequence> <xs:attribute name='from' type='xs:string' use='optional'/> <xs:attribute name='id' type='xs:NMTOKEN' use='optional'/> <xs:attribute name='to' type='xs:string' use='optional'/> <xs:attribute name='type' use='optional'> <xs:simpleType> <xs:restriction base='xs:NCName'> Saint-Andre Expires January 18, 2008 [Page 70]
Internet-Draft XMPP IM July 2007 <xs:enumeration value='error'/> <xs:enumeration value='probe'/> <xs:enumeration value='subscribe'/> <xs:enumeration value='subscribed'/> <xs:enumeration value='unavailable'/> <xs:enumeration value='unsubscribe'/> <xs:enumeration value='unsubscribed'/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute ref='xml:lang' use='optional'/> </xs:complexType> </xs:element> <xs:element name='show'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='away'/> <xs:enumeration value='chat'/> <xs:enumeration value='dnd'/> <xs:enumeration value='xa'/> </xs:restriction> </xs:simpleType> </xs:element> <xs:element name='status'> <xs:complexType> <xs:simpleContent> <xs:extension base='string1024'> <xs:attribute ref='xml:lang' use='optional'/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> <xs:simpleType name='string1024'> <xs:restriction base='xs:string'> <xs:minLength value='1'/> <xs:maxLength value='1024'/> </xs:restriction> </xs:simpleType> <xs:element name='priority' type='xs:byte'/> <xs:element name='iq'> <xs:complexType> <xs:sequence> <xs:any namespace='##other' Saint-Andre Expires January 18, 2008 [Page 71]
Internet-Draft XMPP IM July 2007 minOccurs='0'/> <xs:element ref='error' minOccurs='0'/> </xs:sequence> <xs:attribute name='from' type='xs:string' use='optional'/> <xs:attribute name='id' type='xs:NMTOKEN' use='required'/> <xs:attribute name='to' type='xs:string' use='optional'/> <xs:attribute name='type' use='required'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='error'/> <xs:enumeration value='get'/> <xs:enumeration value='result'/> <xs:enumeration value='set'/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute ref='xml:lang' use='optional'/> </xs:complexType> </xs:element> <xs:element name='error'> <xs:complexType> <xs:sequence xmlns:err='urn:ietf:params:xml:ns:xmpp-stanzas'> <xs:group ref='err:stanzaErrorGroup'/> <xs:element ref='err:text' minOccurs='0'/> </xs:sequence> <xs:attribute name='code' type='xs:unsignedShort' use='optional'/> <xs:attribute name='type' use='required'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='auth'/> <xs:enumeration value='cancel'/> <xs:enumeration value='continue'/> <xs:enumeration value='modify'/> <xs:enumeration value='wait'/> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> Saint-Andre Expires January 18, 2008 [Page 72]
Internet-Draft XMPP IM July 2007 </xs:schema> D.2. jabber:server <?xml version='1.0' encoding='UTF-8'?> <xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema' targetNamespace='jabber:server' xmlns='jabber:server' elementFormDefault='qualified'> <xs:import namespace='urn:ietf:params:xml:ns:xmpp-stanzas'/> <xs:element name='message'> <xs:complexType> <xs:sequence> <xs:choice minOccurs='0' maxOccurs='unbounded'> <xs:element ref='subject'/> <xs:element ref='body'/> <xs:element ref='thread'/> </xs:choice> <xs:any namespace='##other' minOccurs='0' maxOccurs='unbounded'/> <xs:element ref='error' minOccurs='0'/> </xs:sequence> <xs:attribute name='from' type='xs:string' use='required'/> <xs:attribute name='id' type='xs:NMTOKEN' use='optional'/> <xs:attribute name='to' type='xs:string' use='required'/> <xs:attribute name='type' use='optional' default='normal'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='chat'/> <xs:enumeration value='error'/> <xs:enumeration value='groupchat'/> <xs:enumeration value='headline'/> <xs:enumeration value='normal'/> </xs:restriction> </xs:simpleType> </xs:attribute> Saint-Andre Expires January 18, 2008 [Page 73]
Internet-Draft XMPP IM July 2007 <xs:attribute ref='xml:lang' use='optional'/> </xs:complexType> </xs:element> <xs:element name='body'> <xs:complexType> <xs:simpleContent> <xs:extension base='xs:string'> <xs:attribute ref='xml:lang' use='optional'/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> <xs:element name='subject'> <xs:complexType> <xs:simpleContent> <xs:extension base='xs:string'> <xs:attribute ref='xml:lang' use='optional'/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> <xs:element name='thread' type='xs:NMTOKEN'/> <xs:element name='presence'> <xs:complexType> <xs:sequence> <xs:choice minOccurs='0' maxOccurs='unbounded'> <xs:element ref='show'/> <xs:element ref='status'/> <xs:element ref='priority'/> </xs:choice> <xs:any namespace='##other' minOccurs='0' maxOccurs='unbounded'/> <xs:element ref='error' minOccurs='0'/> </xs:sequence> <xs:attribute name='from' type='xs:string' use='required'/> <xs:attribute name='id' type='xs:NMTOKEN' use='optional'/> <xs:attribute name='to' type='xs:string' Saint-Andre Expires January 18, 2008 [Page 74]
Internet-Draft XMPP IM July 2007 use='required'/> <xs:attribute name='type' use='optional'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='error'/> <xs:enumeration value='probe'/> <xs:enumeration value='subscribe'/> <xs:enumeration value='subscribed'/> <xs:enumeration value='unavailable'/> <xs:enumeration value='unsubscribe'/> <xs:enumeration value='unsubscribed'/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute ref='xml:lang' use='optional'/> </xs:complexType> </xs:element> <xs:element name='show'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='away'/> <xs:enumeration value='chat'/> <xs:enumeration value='dnd'/> <xs:enumeration value='xa'/> </xs:restriction> </xs:simpleType> </xs:element> <xs:element name='status'> <xs:complexType> <xs:simpleContent> <xs:extension base='string1024'> <xs:attribute ref='xml:lang' use='optional'/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> <xs:simpleType name='string1024'> <xs:restriction base='xs:string'> <xs:minLength value='1'/> <xs:maxLength value='1024'/> </xs:restriction> </xs:simpleType> <xs:element name='priority' type='xs:byte'/> Saint-Andre Expires January 18, 2008 [Page 75]
Internet-Draft XMPP IM July 2007 <xs:element name='iq'> <xs:complexType> <xs:sequence> <xs:any namespace='##other' minOccurs='0'/> <xs:element ref='error' minOccurs='0'/> </xs:sequence> <xs:attribute name='from' type='xs:string' use='required'/> <xs:attribute name='id' type='xs:NMTOKEN' use='required'/> <xs:attribute name='to' type='xs:string' use='required'/> <xs:attribute name='type' use='required'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='error'/> <xs:enumeration value='get'/> <xs:enumeration value='result'/> <xs:enumeration value='set'/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute ref='xml:lang' use='optional'/> </xs:complexType> </xs:element> <xs:element name='error'> <xs:complexType> <xs:sequence xmlns:err='urn:ietf:params:xml:ns:xmpp-stanzas'> <xs:group ref='err:stanzaErrorGroup'/> <xs:element ref='err:text' minOccurs='0'/> </xs:sequence> <xs:attribute name='code' type='xs:unsignedShort' use='optional'/> <xs:attribute name='type' use='required'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='auth'/> <xs:enumeration value='cancel'/> <xs:enumeration value='continue'/> <xs:enumeration value='modify'/> <xs:enumeration value='wait'/> </xs:restriction> Saint-Andre Expires January 18, 2008 [Page 76]
Internet-Draft XMPP IM July 2007 </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> </xs:schema> D.3. jabber:iq:roster <?xml version='1.0' encoding='UTF-8'?> <xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema' targetNamespace='jabber:iq:roster' xmlns='jabber:iq:roster' elementFormDefault='qualified'> <xs:element name='query'> <xs:complexType> <xs:sequence> <xs:element ref='item' minOccurs='0' maxOccurs='unbounded'/> </xs:sequence> </xs:complexType> </xs:element> <xs:element name='item'> <xs:complexType> <xs:sequence> <xs:element ref='group' minOccurs='0' maxOccurs='unbounded'/> </xs:sequence> <xs:attribute name='ask' use='optional'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='subscribe'/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute name='jid' type='xs:string' use='required'/> <xs:attribute name='name' type='xs:string' use='optional'/> <xs:attribute name='subscription' use='optional'> <xs:simpleType> <xs:restriction base='xs:NCName'> <xs:enumeration value='both'/> <xs:enumeration value='from'/> Saint-Andre Expires January 18, 2008 [Page 77]
Internet-Draft XMPP IM July 2007 <xs:enumeration value='none'/> <xs:enumeration value='remove'/> <xs:enumeration value='to'/> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> <xs:element name='group' type='xs:string'/> </xs:schema> Appendix E. Differences From RFC 3921 Based on consensus derived from implementation and deployment experience as well as formal interoperability testing, the following substantive modifications were made from RFC 3921. o The protocol for session establishment was determined to be unnecessary and therefore the content previously defined in Section 3 of RFC 3921 was removed. However, server implementations may still want to advertise support for the feature in order to ensure backward-compatibility, even though session establishment is a "no-op". o The protocol for communications blocking specified in Section 10 of RFC 3921 has been moved to [XEP-0016]. o In order to more seamlessly repair lack of synchronization in subscription states between rosters located at different servers, error handling related to presence probes and presence notifications was modified to return presence stanzas of type "unsubscribe" or "unsubscribed" rather than error stanzas. In addition, numerous changes of an editorial nature were made in order to more fully specify and clearly explain the protocols. Appendix F. Copying Conditions The Contributor grants third parties the irrevocable right to copy, use and distribute the Contribution, with or without modification, in any medium, without royalty, provided that, unless separate permission is granted, redistributed modified works: 1. do not contain misleading author, version, name of work, or endorsement information, and Saint-Andre Expires January 18, 2008 [Page 78]
Internet-Draft XMPP IM July 2007 2. do not claim endorsement of the modified work by the Contributor, or any organization the Contributor belongs to, the Internet Engineering Task Force (IETF), Internet Research Task Force (IRTF), Internet Engineering Steering Group (IESG), Internet Architecture Board (IAB), Internet Assigned Numbers Authority (IANA), Internet Society (ISOC), Request For Comments (RFC) Editor, or any combination or variation of such terms (including without limitation the IETF "4 diamonds" logo), or any terms that are confusingly similar thereto, and 3. remove any claims of status as an Internet Standard, including without limitation removing the RFC boilerplate. The IETF suggests that any citation or excerpt of unmodified text reference the RFC or other document from which the text is derived. Index A Available Resource 29 B Broadcasted Presence 28 C Contact 18 D Directed Presence 28 I Initial Presence 29 Interested Resource 9 P Presence Probe 30 Presence Session 28 Presence Subscription 18 Presence 4 R Roster Get 7 Roster Push 8 Roster Result 8 Roster Set 7 Roster 4 S Saint-Andre Expires January 18, 2008 [Page 79]
Internet-Draft XMPP IM July 2007 Subscription Request 18 U Unavailable Presence 34 Author's Address Peter Saint-Andre (editor) XMPP Standards Foundation P.O. Box 1641 Denver, CO 80201 US Email: stpeter@jabber.org URI: xmpp:stpeter@jabber.org Saint-Andre Expires January 18, 2008 [Page 80]
Internet-Draft XMPP IM July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Saint-Andre Expires January 18, 2008 [Page 81]