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This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.
This Internet-Draft will expire on March 7, 2004.
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document describes the core features of the Extensible Messaging and Presence Protocol (XMPP), a protocol for streaming XML[1] elements in order to exchange messages and presence information in close to real time. While XMPP provides a generalized, extensible framework for transporting structured information, it is used mainly for the purpose of building instant messaging and presence applications that meet the requirements of RFC 2779.
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The Extensible Messaging and Presence Protocol (XMPP) is an open XML[1] protocol for near-real-time messaging, presence, and request-response services. The basic syntax and semantics were developed originally within the Jabber open-source community, mainly in 1999. In 2002, the XMPP WG was chartered with developing an adaptation of the Jabber protocol that would be suitable as an IETF instant messaging (IM) and presence technology. As a result of work by the XMPP WG, the current document defines the core features of XMPP; XMPP IM[20] defines the extensions required to provide the instant messaging and presence functionality defined in RFC 2779[2].
The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119[3].
The authors welcome discussion and comments related to the topics presented in this document. The preferred forum is the <xmppwg@jabber.org> mailing list, for which archives and subscription information are available at <http://www.jabber.org/cgi-bin/mailman/listinfo/xmppwg/>.
This document is in full compliance with all provisions of Section 10 of RFC 2026. Parts of this specification use the term "jabber" for identifying namespaces and other protocol syntax. Jabber[tm] is a registered trademark of Jabber, Inc. Jabber, Inc. grants permission to the IETF for use of the Jabber trademark in association with this specification and its successors, if any.
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Although XMPP is not wedded to any specific network architecture, to this point it usually has been implemented via a typical client-server architecture, wherein a client utilizing XMPP accesses a server over a TCP[4] socket.
The following diagram provides a high-level overview of this architecture (where "-" represents communications that use XMPP and "=" represents communications that use any other protocol).
C1 - S1 - S2 - C3
/ \
C2 - G1 = FN1 = FC1
The symbols are as follows:
A server acts as an intelligent abstraction layer for XMPP communications. Its primary responsibilities are to manage connections from or sessions for other entities (in the form of XML streams to and from authorized clients, servers, and other entities) and to route appropriately-addressed XML stanzas among such entities over XML streams. Most XMPP-compliant servers also assume responsibility for the storage of data that is used by clients (e.g., contact lists for users of XMPP-based instant messaging and presence applications); in this case, the XML data is processed directly by the server itself on behalf of the client and is not routed to another entity. Compliant server implementations MUST ensure in-order processing of XML stanzas between any two entities.
Most clients connect directly to a server over a TCP socket and use XMPP to take full advantage of the functionality provided by a server and any associated services. Although there is no necessary coupling of an XML stream to a TCP socket (e.g., a client COULD connect via HTTP[21] polling or some other mechanism), this specification defines a binding of XMPP to TCP only. Multiple resources (e.g., devices or locations) MAY connect simultaneously to a server on behalf of each authorized client, with each resource connecting over a discrete TCP socket and differentiated by the resource identifier of a JID (e.g., <user@domain/home> vs. <user@domain/work>) as defined under Addressing Scheme. The port registered with the Internet Assigned Numbers Authority (IANA)[5] for connections between a client and a server is 5222 (see IANA Considerations).
A gateway is a special-purpose server-side service whose primary function is to translate XMPP into the protocol used by a foreign (non-XMPP) messaging system, as well as to translate the return data back into XMPP. Examples are gateways to Internet Relay Chat (IRC), Short Message Service (SMS), SMTP, and legacy instant messaging networks such as AIM, ICQ, MSN Messenger, and Yahoo! Instant Messenger. Communications between gateways and servers, and between gateways and the foreign messaging system, are not defined in this document.
Because each server is identified by a network address and because server-to-server communications are a straightforward extension of the client-to-server protocol, in practice the system consists of a network of servers that inter-communicate. Thus user-a@domain1 is able to exchange messages, presence, and other information with user-b@domain2. This pattern is familiar from messaging protocols (such as SMTP) that make use of network addressing standards. Communications between any two servers are OPTIONAL; if enabled, such communications occur over XML streams that are normally bound to TCP sockets, using port 5269 as registered with the IANA (see IANA Considerations).
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An entity is anything that can be considered a network endpoint (i.e., an ID on the network) and that can communicate using XMPP. All such entities are uniquely addressable in a form that is consistent with RFC 2396[22]. For historical reasons, the address of such an entity is called a Jabber Identifier or JID. A valid JID contains a set of ordered elements formed of a domain identifier, node identifier, and resource identifier in the following format: [node@]domain[/resource]. Each allowable portion of a JID (node identifier, domain identifier, and resource identifier) may be up to 1023 bytes in length, resulting in a maximum total size (including the '@' and '/' separators) of 3071 bytes.
All JIDs are based on the foregoing structure. The most common use of this structure is to identify an instant messaging user, the server to which the user connects, and the user's active session or connection (e.g., a specific client) in the form of <user@domain/resource>. However, node types other than clients are possible; for example, a specific chat room offered by a multi-user chat service could be addressed as <room@service> (where "room" is the name of the chat room and "service" is the hostname of the multi-user chat service) and a specific occupant of such a room could be addressed as <room@service/nick> (where "nick" is the occupant's room nickname). Many other JID types are possible (e.g., <domain/resource> could be a server-side script or service).
The domain identifier is the primary identifier and is the only REQUIRED element of a JID (a mere domain identifier is a valid JID). It usually represents the network gateway or "primary" server to which other entities connect for XML routing and data management capabilities. However, the entity referenced by a domain identifier is not always a server, and may be a service that is addressed as a subdomain of a server and that provides functionality above and beyond the capabilities of a server (e.g., a multi-user chat service, a user directory, or a gateway to a foreign messaging system).
The domain identifier for every server or service that will communicate over a network SHOULD resolve to a Fully Qualified Domain Name. A domain identifier MUST conform to RFC 952[6] and RFC 1123[7]. In addition, a domain identifier MUST be no more than 1023 bytes in length and MUST conform to the Nameprep[8] profile of stringprep[9].
The node identifier is an optional secondary identifier placed before the domain identifier and separated from the latter by the '@' character. It usually represents the entity requesting and using network access provided by the server or gateway (i.e., a client), although it can also represent other kinds of entities (e.g., a chat room associated with a multi-user chat service). The entity represented by a node identifier is addressed within the context of a specific domain; within instant messaging and presence applications of XMPP this address is called a "bare JID" and is of the form <node@domain>.
A node identifier MUST be no more than 1023 bytes in length and MUST conform to the Nodeprep profile of stringprep[9].
The resource identifier is an optional tertiary identifier placed after the domain identifier and separated from the latter by the '/' character. A resource identifier may modify either a <user@domain> or mere <domain> address. It usually represents a specific session, connection (e.g., a device or location), or object (e.g., a participant in a multi-user chat room) belonging to the entity associated with a node identifier. A resource identifier is opaque to both servers and other clients, and is typically defined by a client implementation when it provides the information necessary to complete stream authentication. An entity may maintain multiple resources simultaneously.
A resource identifier MUST be no more than 1023 bytes in length and MUST conform to the Resourceprep profile of stringprep[9].
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Two fundamental concepts make possible the rapid, asynchronous exchange of relatively small payloads of structured information between presence-aware entities: XML streams and XML stanzas. These terms may be defined as follows:
- Definition of XML Stream:
- An XML stream is a container for the exchange of XML elements between any two entities over a network. An XML stream is negotiated from an initiating entity (usually a client or server) to a receiving entity (usually a server), normally over a TCP socket, and corresponds to the initiating entity's "session" with the receiving entity. The start of the XML stream is denoted unambiguously by an opening XML <stream> tag (with appropriate attributes and namespace declarations), while the end of the XML stream is denoted unambiguously by a closing XML </stream> tag. An XML stream is unidirectional; in order to enable bidirectional information exchange, the initiating entity and receiving entity MUST negotiate one stream in each direction (the "initial stream" and the "response stream"), normally over the same TCP connection.
- Definition of XML Stanza:
- An XML stanza is a discrete semantic unit of structured information that is sent from one entity to another over an XML stream. An XML stanza exists at the direct child level of the root <stream/> element and is said to be well-balanced if it matches production [43] content of the XML specification[1]). The start of any XML stanza is denoted unambiguously by the element start tag at depth=1 of the XML stream (e.g., <presence>), and the end of any XML stanza is denoted unambiguously by the corresponding close tag at depth=1 (e.g., </presence>). An XML stanza MAY contain child elements (with accompanying attributes, elements, and CDATA) as necessary in order to convey the desired information. An XML element sent for the purpose of stream encryption, stream authentication, or server dialback is not considered to be an XML stanza.
Consider the example of a client's session with a server. In order to connect to a server, a client MUST initiate an XML stream by sending an opening <stream> tag to the server, optionally preceded by a text declaration specifying the XML version supported and the character encoding (see also Character Encoding). The server SHOULD then reply with a second XML stream back to the client, again optionally preceded by a text declaration. Once the client has authenticated with the server (see Section 6), the client MAY send an unlimited number of XML stanzas over the stream to any recipient on the network. When the client desires to close the stream, it simply sends a closing </stream> tag to the server (alternatively, the stream may be closed by the server), after which both the client and server SHOULD close the underlying TCP connection as well.
Those who are accustomed to thinking of XML in a document-centric manner may wish to view a client's session with a server as consisting of two open-ended XML documents: one from the client to the server and one from the server to the client. From this perspective, the root <stream/> element can be considered the document entity for each "document", and the two "documents" are built up through the accumulation of XML stanzas sent over the two XML streams. However, this perspective is a convenience only, and XMPP does not deal in documents but in XML streams and XML stanzas.
In essence, then, an XML stream acts as an envelope for all the XML stanzas sent during a session. We can represent this graphically as follows:
|--------------------|
| <stream> |
|--------------------|
| <presence> |
| <show/> |
| </presence> |
|--------------------|
| <message to='foo'> |
| <body/> |
| </message> |
|--------------------|
| <iq to='bar'> |
| <query/> |
| </iq> |
|--------------------|
| ... |
|--------------------|
| </stream> |
|--------------------|
The attributes of the stream element are as follows:
We can summarize as follows:
| initiating to receiving | receiving to initiating
------------------------------------------------------------
to | hostname of receiver | silently ignored
from | silently ignored | hostname of receiver
id | silently ignored | session key
version | signals XMPP 1.0 support | signals XMPP 1.0 support
The following rules apply to the generation and handling of the 'version' attribute:
The stream element MUST possess both a stream namespace declaration and a default namespace declaration (as "namespace declaration" is defined in the XML namespaces specification[10]). For detailed information regarding the stream namespace and default namespace, see Namespace Names and Prefixes.
If the initiating entity includes the 'version' attribute set to a value of "1.0" in its initiating stream element, the receiving entity MUST send a <features/> child element (prefixed by the stream namespace prefix) to the initiating entity in order to announce any stream-level features that can be negotiated (or capabilities that otherwise need to be advertised). Currently this is used for TLS and SASL negotiation only, but it could be used for other negotiable features in the future (usage is defined under Stream Encryption and Stream Authentication below). If an entity does not understand or support some features, it SHOULD silently ignore them.
XML streams in XMPP 1.0 SHOULD be encrypted as defined under Stream Encryption and MUST be authenticated as defined under Stream Authentication. If the initiating entity attempts to send an XML stanza before the stream is authenticated, the receiving entity SHOULD return a <not-authorized/> stream error to the initiating entity and then terminate both the XML stream and the underlying TCP connection.
The root stream element MAY contain an <error/> child element that is prefixed by the stream namespace prefix. The error child MUST be sent by a compliant entity (usually a server rather than a client) if it perceives that a stream-level error has occurred.
The following rules apply to stream-level errors:
The syntax for stream errors is as follows:
<stream:error>
<defined-condition xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
<text xmlns='urn:ietf:params:xml:ns:xmpp-streams'>
OPTIONAL descriptive text
</text>
[OPTIONAL application-specific condition element]
</stream:error>
The <error/> element:
The <text/> element is OPTIONAL. If included, it SHOULD be used only to provide descriptive or diagnostic information that supplements the meaning of a defined condition or application-specific condition. It SHOULD NOT be interpreted programmatically by an application. It SHOULD NOT be used as the error message presented to user, but MAY be shown in addition to the error message associated with the included condition element (or elements).
Note: the XML namespace name 'urn:ietf:params:xml:ns:xmpp-streams' that qualifies the descriptive element adheres to the format defined in The IETF XML Registry[23].
The following stream-level error conditions are defined:
As noted, an application MAY provide application-specific stream error information by including a properly-namespaced child in the error element. The application-specific element SHOULD supplement or further qualify a defined element. Thus the <error/> element will contain two or three child elements:
<stream:error>
<xml-not-well-formed
xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
<text xml:lang='en' xmlns='urn:ietf:params:xml:ns:xmpp-streams'>
Some special application diagnostic information!
</text>
<escape-your-data xmlns='application-ns'/>
</stream:error>
</stream:stream>
The following is a stream-based session of a client on a server (where the "C" lines are sent from the client to the server, and the "S" lines are sent from the server to the client):
A basic session:
C: <?xml version='1.0'?>
<stream:stream
to='example.com'
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
version='1.0'>
S: <?xml version='1.0'?>
<stream:stream
from='example.com'
id='id_123456789'
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
version='1.0'>
... authentication ...
C: <message from='juliet@example.com'
to='romeo@example.net'
xml:lang='en'>
C: <body>Art thou not Romeo, and a Montague?</body>
C: </message>
S: <message from='romeo@example.net'
to='juliet@example.com'
xml:lang='en'>
S: <body>Neither, fair saint, if either thee dislike.</body>
S: </message>
C: </stream:stream>
S: </stream:stream>
A stream gone bad:
C: <?xml version='1.0'?>
<stream:stream
to='example.com'
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
version='1.0'>
S: <?xml version='1.0'?>
<stream:stream
from='example.com'
id='id_123456789'
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
version='1.0'>
... authentication ...
C: <message xml:lang='en'>
<body>Bad XML, no closing body tag!
</message>
S: <stream:error>
<xml-not-well-formed
xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
</stream:error>
S: </stream:stream>
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XMPP includes a method for securing the stream from tampering and eavesdropping. This channel encryption method makes use of the Transport Layer Security (TLS)[11] protocol, along with a "STARTTLS" extension that is modelled after similar extensions for the IMAP[24], POP3[25], and ACAP[26] protocols as described in RFC 2595[27]. The namespace name for the STARTTLS extension is 'urn:ietf:params:xml:ns:xmpp-tls', which adheres to the format defined in The IETF XML Registry[23].
An administrator of a given domain MAY require the use of TLS for client-to-server communications, server-to-server communications, or both. Servers SHOULD use TLS between two domains for the purpose of securing server-to-server communications. See Mandatory to Implement Technologies regarding mechanisms that MUST be supported.
The following rules apply:
- Case 1 -- The initiating entity has been configured with a set of trusted root certificates:
- Normal certificate validation processing is appropriate, and SHOULD follow the rules defined for HTTP over TLS[12]. The trusted roots may be either a well-known public set or a manually configured Root CA (e.g., an organization's own Certificate Authority or a self-signed Root CA for the service as described under High Security). This case is RECOMMENDED.
- Case 2 -- The initiating entity has been configured with the receiving entity's self-signed service certificate:
- Simple comparison of public keys is appropriate. This case is NOT RECOMMENDED (see High Security for details).
If the above methods fail, the certificate SHOULD be presented to a human (e.g., an end user or server administrator) for approval; if presented, the receiver MUST deliver the entire certificate chain to the human, who SHOULD be given the option to store the Root CA certificate (not the service or End Entity certificate) and to not be queried again regarding acceptance of the certificate for some reasonable period of time.
When an initiating entity secures a stream with a receiving entity, the steps involved are as follows:
The following example shows the data flow for a client securing a stream using STARTTLS (the IANA-registered port 5222 SHOULD be used; see IANA Considerations).
Step 1: Client initiates stream to server:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
to='capulet.com'
version='1.0'>
Step 2: Server responds by sending a stream tag to client:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
id='12345678'
from='capulet.com'
version='1.0'>
Step 3: Server sends the STARTTLS extension to client along with authentication mechanisms and any other stream features:
<stream:features>
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'>
<required/>
</starttls>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>PLAIN</mechanism>
</mechanisms>
</stream:features>
Step 4: Client sends the STARTTLS command to server:
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5: Server informs client to proceed:
<proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5 (alt): Server informs client that TLS negotiation has failed and closes both stream and TCP connection:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
</stream:stream>
Step 6: Client and server attempt to complete TLS negotiation over the existing TCP connection.
Step 7: If TLS negotiation is successful, client initiates a new stream to server:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
to='capulet.com'
version='1.0'>
Step 7 (alt): If TLS negotiation is unsuccessful, server MUST close TCP connection.
Step 8: Server responds by sending a stream header to client along with any remaining negotiable stream features:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
from='capulet.com'
id='12345678'
version='1.0'>
<stream:features>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>PLAIN</mechanism>
<mechanism>EXTERNAL</mechanism>
</mechanisms>
</stream:features>
Step 9: Client SHOULD continue with Stream Authentication.
The following example shows the data flow for two servers securing a stream using STARTTLS (the IANA-registered port 5269 SHOULD be used; see IANA Considerations).
Step 1: Server1 initiates stream to Server2:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
to='montague.net'
version='1.0'>
Step 2: Server2 responds by sending a stream tag to Server1:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
from='montague.net'
id='12345678'
version='1.0'>
Step 3: Server2 sends the STARTTLS extension to Server1 along with authentication mechanisms and any other stream features:
<stream:features>
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
<required/>
</starttls>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>KERBEROS_V4</mechanism>
</mechanisms>
</stream:features>
Step 4: Server1 sends the STARTTLS command to Server2:
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5: Server2 informs Server1 to proceed:
<proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
Step 5 (alt): Server2 informs Server1 that TLS negotiation has failed and closes stream:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
</stream:stream>
Step 6: Server1 and Server2 attempt to complete TLS negotiation via TCP.
Step 7: If TLS negotiation is successful, Server1 initiates a new stream to Server2:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
to='montague.net'
version='1.0'>
Step 7 (alt): If TLS negotiation is unsuccessful, server MUST close TCP connection.
Step 8: Server2 responds by sending a stream header to Server1 along with any remaining negotiable stream features:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
from='montague.net'
id='12345678'
version='1.0'>
<stream:features>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>KERBEROS_V4</mechanism>
<mechanism>EXTERNAL</mechanism>
</mechanisms>
</stream:features>
Step 9: Server1 SHOULD continue with Stream Authentication.
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XMPP includes a method for authenticating a stream using an XMPP adaptation of the Simple Authentication and Security Layer (SASL)[13]. SASL provides a generalized method for adding authentication support to connection-based protocols, and XMPP uses a generic XML namespace profile for SASL that conforms to section 4 ("Profiling Requirements") of RFC 2222[13] (the XMPP-specific namespace name is 'urn:ietf:params:xml:ns:xmpp-sasl', which adheres to the format defined in The IETF XML Registry[23]). Finally, see Mandatory to Implement Technologies regarding mechanisms that MUST be supported.
The following rules apply:
When an initiating entity authenticates with a receiving entity, the steps involved are as follows:
This series of challenge/response pairs continues until one of three things happens:
The following SASL-related error conditions are defined:
Section 4 of the SASL specification[13] requires that the following information be supplied by a protocol definition:
- service name:
- "xmpp"
- initiation sequence:
- After the initiating entity provides an opening XML stream header and the receiving entity replies in kind, the receiving entity provides a list of acceptable authentication methods. The initiating entity chooses one method from the list and sends it to the receiving entity as the value of the 'mechanism' attribute possessed by an <auth/> element, optionally including an initial response to avoid a round trip.
- exchange sequence:
- Challenges and responses are carried through the exchange of <challenge/> elements from receiving entity to initiating entity and <response/> elements from initiating entity to receiving entity. The receiving entity reports failure by sending a <failure/> element and success by sending a <success/> element; the initiating entity aborts the exchange by sending an <abort/> element. (All of these elements are qualified by the 'urn:ietf:params:xml:ns:xmpp-sasl' namespace.) Upon successful negotiation, both sides consider the original XML stream closed and new <stream> headers are sent by both entities.
- security layer negotiation:
- The security layer takes effect immediately after sending the closing ">" character of the <success/> element for the server, and immediately after receiving the closing ">" character of the <success/> element for the client (this element is qualified by the 'urn:ietf:params:xml:ns:xmpp-sasl' namespace).
- use of the authorization identity:
- The authorization identity is used by xmpp to denote the "full JID" (<user@domain/resource>) of a client or the sending domain of a server.
The following example shows the data flow for a client authenticating with a server using SASL (the IANA-registered port 5222 SHOULD be used; see IANA Considerations).
Step 1: Client initiates stream to server:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
to='capulet.com'
version='1.0'>
Step 2: Server responds with a stream tag sent to client:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
id='12345678'
from='capulet.com'
version='1.0'>
Step 3: Server informs client of available authentication mechanisms:
<stream:features>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>PLAIN</mechanism>
</mechanisms>
</stream:features>
Step 4: Client selects an authentication mechanism:
<auth
xmlns='urn:ietf:params:xml:ns:xmpp-sasl'
mechanism='DIGEST-MD5'/>
Step 5: Server sends a base64-encoded challenge to client:
<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi
xxb3A9ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz
</challenge>
The decoded challenge is:
realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",\
qop="auth",charset=utf-8,algorithm=md5-sess
Step 5 (alt): Server returns error to client:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism-too-weak/>
</failure>
</stream:stream>
Step 6: Client responds to the challenge:
<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
dXNlcm5hbWU9InJvYiIscmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik
9BNk1HOXRFUUdtMmhoIixjbm9uY2U9Ik9BNk1IWGg2VnFUclJrIixuYz0w
MDAwMDAwMSxxb3A9YXV0aCxkaWdlc3QtdXJpPSJ4bXBwL2NhdGFjbHlzbS
5jeCIscmVzcG9uc2U9ZDM4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZjIxNDNh
ZjcsY2hhcnNldD11dGYtOCxhdXRoemlkPSJyb2JAY2F0YWNseXNtLmN4L2
15UmVzb3VyY2Ui
</response>
The decoded response is:
username="rob",realm="cataclysm.cx",\
nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk",\
nc=00000001,qop=auth,digest-uri="xmpp/cataclysm.cx",\
response=d388dad90d4bbd760a152321f2143af7,charset=utf-8,\
authzid="rob@cataclysm.cx/myResource"
Step 7: Server sends another challenge to client:
<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
</challenge>
The decoded challenge is:
rspauth=ea40f60335c427b5527b84dbabcdfffd
Step 7 (alt): Server returns error to client:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<invalid-realm/>
</failure>
</stream:stream>
Step 8: Client responds to the challenge:
<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 9: Server informs client of successful authentication:
<success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 9 (alt): Server informs client of failed authentication:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<temporary-auth-failure/>
</failure>
</stream:stream>
Step 10: Client initiates a new stream to server:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
to='capulet.com'
version='1.0'>
Step 11: Server responds by sending a stream header to client along with any additional features (or an empty features element):
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
id='12345678'
from='capulet.com'
version='1.0'>
<stream:features/>
The following example shows the data flow for a server authenticating with another server using SASL (the IANA-registered port 5269 SHOULD be used; see IANA Considerations).
Step 1: Server1 initiates stream to Server2:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
to='montague.net'
version='1.0'>
Step 2: Server2 responds with a stream tag sent to Server1:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
from='montague.net'
id='12345678'
version='1.0'>
Step 3: Server2 informs Server1 of available authentication mechanisms:
<stream:features>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>KERBEROS_V4</mechanism>
</mechanisms>
</stream:features>
Step 4: Server1 selects an authentication mechanism:
<auth
xmlns='urn:ietf:params:xml:ns:xmpp-sasl'
mechanism='DIGEST-MD5'/>
Step 5: Server2 sends a base64-encoded challenge to Server1:
<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi
xxb3A9ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz
</challenge>
The decoded challenge is:
realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",\
qop="auth",charset=utf-8,algorithm=md5-sess
Step 5 (alt): Server2 returns error to Server1:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<encryption-required/>
</failure>
</stream:stream>
Step 6: Server1 responds to the challenge:
<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi
xjbm9uY2U9Ik9BNk1IWGg2VnFUclJrIixuYz0wMDAwMDAwMSxxb3A9YXV0
aCxkaWdlc3QtdXJpPSJ4bXBwL2NhdGFjbHlzbS5jeCIscmVzcG9uc2U9ZD
M4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZjIxNDNhZjcsY2hhcnNldD11dGYt
OAo=
</response>
The decoded response is:
realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk",\
nc=00000001,qop=auth,digest-uri="xmpp/cataclysm.cx",\
response=d388dad90d4bbd760a152321f2143af7,charset=utf-8
Step 7: Server2 sends another challenge to Server1:
<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
</challenge>
The decoded challenge is:
rspauth=ea40f60335c427b5527b84dbabcdfffd
Step 5 (alt): Server2 returns error to Server1:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<invalid-authzid/>
</failure>
</stream:stream>
Step 8: Server1 responds to the challenge:
<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 9: Server2 informs Server1 of successful authentication:
<success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 9 (alt): Server2 informs Server1 of failed authentication:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<temporary-auth-failure/>
</failure>
</stream:stream>
Step 10: Server1 initiates a new stream to Server2:
<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
to='montague.net'
version='1.0'>
Step 11: Server2 responds by sending a stream header to Server1 along with any additional features (or an empty features element):
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
from='montague.net'
id='12345678'
version='1.0'>
<stream:features/>
| TOC |
The Jabber protocol from which XMPP was adapted includes a "server dialback" method for protecting against domain spoofing, thus making it more difficult to spoof XML stanzas (see Server-to-Server Communications regarding this method's security characteristics). Server dialback also makes it easier to deploy systems in which outbound messages and inbound messages are handled by different machines for the same domain. The server dialback method is made possible by the existence of DNS, since one server can (normally) discover the authoritative server for a given domain.
Because dialback depends on the Domain Name System, inter-domain communications MUST NOT proceed until the DNS hostnames asserted by the servers have been resolved (see Server-to-Server Communications).
The method for generating and verifying the keys used in server dialback MUST take into account the hostnames being used, the random ID generated for the stream, and a secret known by the authoritative server's network.
Any error that occurs during dialback negotiation MUST be considered a stream error, resulting in termination of the stream and of the underlying TCP connection. The possible error conditions are specified in the protocol description below.
The following terminology applies:
The following is a brief summary of the order of events in dialback:
We can represent this flow of events graphically as follows:
Originating Receiving
Server Server
----------- ---------
| |
| establish connection |
| ----------------------> |
| |
| send stream header |
| ----------------------> |
| |
| send stream header |
| <---------------------- |
| | Authoritative
| send dialback key | Server
| ----------------------> | -------------
| | |
| establish connection |
| ----------------------> |
| |
| send stream header |
| ----------------------> |
| |
| establish connection |
| <---------------------- |
| |
| send stream header |
| <---------------------- |
| |
| send dialback key |
| ----------------------> |
| |
| validate dialback key |
| <---------------------- |
|
| report dialback result |
| <---------------------- |
| |
The interaction between the servers is as follows:
<stream:stream
xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server'
xmlns:db='jabber:server:dialback'>
Note: the 'to' and 'from' attributes are NOT REQUIRED on the root stream element. The inclusion of the xmlns:db namespace declaration with the name shown indicates to Receiving Server that Originating Server supports dialback. If the namespace name is incorrect, then Receiving Server MUST generate an <invalid-namespace/> stream error condition and terminate both the XML stream and the underlying TCP connection.
<stream:stream
xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server'
xmlns:db='jabber:server:dialback'
id='457F9224A0...'>
Note: The 'to' and 'from' attributes are NOT REQUIRED on the root stream element. If the namespace name is incorrect, then Originating Server MUST generate an <invalid-namespace/> stream error condition and terminate both the XML stream and the underlying TCP connection. Note well that Receiving Server is NOT REQUIRED to reply and MAY silently terminate the XML stream and underlying TCP connection depending on security policies in place.
<db:result
to='Receiving Server'
from='Originating Server'>
98AF014EDC0...
</db:result>
Note: this key is not examined by Receiving Server, since Receiving Server does not keep information about Originating Server between sessions. The key generated by Originating Server MUST be based in part on the value of the ID provided by Receiving Server in the previous step, and in part on a secret shared by Originating Server and Authoritative Server. If the value of the 'to' address does not match a hostname recognized by Receiving Server, then Receiving Server MUST generate a <host-unknown/> stream error condition and terminate both the XML stream and the underlying TCP connection. If the value of the 'from' address matches a domain with which Receiving Server already has an established connection, then Receiving Server MUST maintain the existing connection until it validates whether the new connection is legitimate; additionally, Receiving Server MAY choose to generate a <not-authorized/> stream error condition for the new connection and then terminate both the XML stream and the underlying TCP connection related to the new request.
<stream:stream
xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server'
xmlns:db='jabber:server:dialback'>
Note: the 'to' and 'from' attributes are NOT REQUIRED on the root stream element. If the namespace name is incorrect, then Authoritative Server MUST generate an <invalid-namespace/> stream error condition and terminate both the XML stream and the underlying TCP connection.
<stream:stream
xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server'
xmlns:db='jabber:server:dialback'
id='1251A342B...'>
Note: if the namespace name is incorrect, then Receiving Server MUST generate an <invalid-namespace/> stream error condition and terminate both the XML stream and the underlying TCP connection between it and Authoritative Server. If a stream error occurs between Receiving Server and Authoritative Server, then Receiving Server MUST generate a <remote-connection-failed/> stream error condition and terminate both the XML stream and the underlying TCP connection between it and Originating Server.
<db:verify
from='Receiving Server'
to='Originating Server'
id='457F9224A0...'>
98AF014EDC0...
</db:verify>
Note: passed here are the hostnames, the original identifier from Receiving Server's stream header to Originating Server in Step 3, and the key that Originating Server sent to Receiving Server in Step 4. Based on this information as well as shared secret information within the Authoritative Server's network, the key is verified. Any verifiable method MAY be used to generate the key. If the value of the 'to' address does not match a hostname recognized by Authoritative Server, then Authoritative Server MUST generate a <host-unknown/> stream error condition and terminate both the XML stream and the underlying TCP connection. If the value of the 'from' address does not match the hostname represented by Receiving Server when opening the TCP connection (or any validated domain), then Authoritative Server MUST generate a <nonmatching-hosts/> stream error condition and terminate both the XML stream and the underlying TCP connection.
<db:verify
from='Originating Server'
to='Receiving Server'
type='valid'
id='457F9224A0...'/>
or
<db:verify
from='Originating Server'
to='Receiving Server'
type='invalid'
id='457F9224A0...'/>
Note: if the ID does not match that provided by Receiving Server in Step 3, then Receiving Server MUST generate an <invalid-id/> stream error condition and terminate both the XML stream and the underlying TCP connection. If the value of the 'to' address does not match a hostname recognized by Receiving Server, then Receiving Server MUST generate a <host-unknown/> stream error condition and terminate both the XML stream and the underlying TCP connection. If the value of the 'from' address does not match the hostname represented by Originating Server when opening the TCP connection (or any validated domain), then Receiving Server MUST generate a <nonmatching-hosts/> stream error condition and terminate both the XML stream and the underlying TCP connection.
<db:result
from='Receiving Server'
to='Originating Server'
type='valid'/>
Note: At this point the connection has either been validated via a type='valid', or reported as invalid. If the connection is invalid, then Receiving Server MUST terminate both the XML stream and the underlying TCP connection. If the connection is validated, data can be sent by Originating Server and read by Receiving Server; before that, all data stanzas sent to Receiving Server SHOULD be silently dropped.
Even if dialback negotiation is successful, a server MUST verify that all XML stanzas received from the other server include a 'from' attribute and a 'to' attribute; if a stanza does not meet this restriction, the server that receives the stanza MUST generate an <improper-addressing/> stream error condition and terminate both the XML stream and the underlying TCP connection. Furthermore, a server MUST verify that the 'from' attribute of stanzas received from the other server includes a validated domain for the stream; if a stanza does not meet this restriction, the server that receives the stanza MUST generate a <nonmatching-hosts/> stream error condition and terminate both the XML stream and the underlying TCP connection. Both of these checks help to prevent spoofing related to particular stanzas.
| TOC |
Once XML streams in both directions have been authenticated and (if desired) encrypted, XML stanzas can be sent over the streams. Three kinds of XML stanza are defined for the 'jabber:client' and 'jabber:server' namespaces: <message/>, <presence/>, and <iq/>. In addition, there are five common attributes for these kinds of stanza. These common attributes and the basic semantics of the three stanza kinds are defined herein; more detailed information regarding the syntax of XML stanzas in relation to instant messaging and presence applications is provided in XMPP IM[20].
The following five attributes are common to message, presence, and IQ stanzas:
The 'to' attribute specifies the JID of the intended recipient for the stanza.
In the 'jabber:client' namespace, a stanza SHOULD possess a 'to' attribute, although a stanza sent from a client to a server for handling by that server (e.g., presence sent to the server for broadcasting to other entities) SHOULD NOT possess a 'to' attribute.
In the 'jabber:server' namespace, a stanza MUST possess a 'to' attribute; if a server receives a stanza that does not meet this restriction, it MUST generate an <improper-addressing/> stream error condition and terminate both the XML stream and the underlying TCP connection with the offending server.
If the value of the 'to' attribute is invalid or cannot be contacted, the entity discovering that fact (usually the sender's or recipient's server) MUST return an appropriate error to the sender.
The 'from' attribute specifies the JID of the sender.
In the 'jabber:client' namespace, a client MUST NOT include a 'from' attribute on the stanzas it sends to a server; if a server receives an XML stanza from a client and the stanza possesses a 'from' attribute, it MUST ignore the value of the 'from' attribute and MAY return an error to the sender. When a client sends an XML stanza within the context of an authenticated stream, the server MUST stamp the stanza with the full JID (<user@domain/resource>) of the connected resource that generated the stanza as defined by the authzid provided in the SASL negotiation. If a client attempts to send an XML stanza before the stream is authenticated, the server SHOULD return a <not-authorized/> stream error to the client and then terminate both the XML stream and the underlying TCP connection.
In the 'jabber:server' namespace, a stanza MUST possess a 'from' attribute; if a server receives a stanza that does not meet this restriction, it MUST generate an <improper-addressing/> stream error condition. Furthermore, the domain identifier portion of the JID contained in the 'from' attribute MUST match the hostname of the sending server (or any validated domain) as communicated in the SASL negotiation or dialback negotiation; if a server receives a stanza that does not meet this restriction, it MUST generate a <nonmatching-hosts/> stream error condition. Both of these conditions MUST result in closing of the stream and termination of the underlying TCP connection.
The optional 'id' attribute MAY be used by a sending entity for internal tracking of stanzas that it sends and receives (especially for tracking the request-response interaction inherent in the use of IQ stanzas). The value of the 'id' attribute is NOT REQUIRED to be unique either globally, within a domain, or within a stream. The semantics of IQ stanzas impose additional restrictions; see the IQ Semantics section of this document.
The 'type' attribute specifies detailed information about the purpose or context of the message, presence, or IQ stanza. The particular allowable values for the 'type' attribute vary depending on whether the stanza is a message, presence, or IQ; the values for message and presence stanzas are specific to instant messaging and presence applications and therefore are defined in XMPP IM[20], whereas the values for IQ stanzas specify the role of an IQ stanza in a structured request-response "conversation" and thus are described under IQ Semantics below. The only 'type' value common to all three stanzas is "error"; see Stanza Errors.
A stanza SHOULD possess an 'xml:lang' attribute (as defined in Section 2.12 of the XML specification[1]) if the stanza contains XML character data that is intended to be presented to a human user (as explained in RFC 2277[14], "internationalization is for humans"). The value of the 'xml:lang' attribute specifies the default language of any such XML character data, which MAY be overridden by the 'xml:lang' attribute of a specific child element. The value of the attribute MUST be an NMTOKEN and MUST conform to the format defined in RFC 3066[15].
The <message/> stanza kind can be seen as a "push" mechanism whereby one entity pushes information to another entity, similar to the communications that occur in a system such as email. All message stanzas SHOULD possess a 'to' attribute that specifies the intended recipient of the message; upon receiving such a stanza, a server SHOULD route or deliver it to the intended recipient (see Server Rules for Handling XML Stanzas for general routing and delivery rules related to XML stanzas).
The <presence/> element can be seen as a basic broadcast or "publish-subscribe" mechanism, whereby multiple entities receive information (in this case, presence information) about an entity to which they have subscribed. In general, a publishing entity SHOULD send a presence stanza with no 'to' attribute, in which case the server to which the entity is connected SHOULD broadcast or multiplex that stanza to all subscribing entities. However, a publishing entity MAY also send a presence stanza with a 'to' attribute, in which case the server SHOULD route or deliver that stanza to the intended recipient. See Server Rules for Handling XML Stanzas for general routing and delivery rules related to XML stanzas, and XMPP IM[20] for presence-specific rules in the context of an instant messaging and presence application.
Info/Query, or IQ, is a request-response mechanism, similar in some ways to HTTP[21]. The semantics of IQ enable an entity to make a request of, and receive a response from, another entity. The data content of the request and response is defined by the namespace declaration of a direct child element of the IQ element, and the interaction is tracked by the requesting entity through use of the 'id' attribute. Thus IQ interactions follow a common pattern of structured data exchange such as get/result or set/result (although an error may be returned in response to a request if appropriate):
Requesting Responding
Entity Entity
---------- ----------
| |
| <iq type='get' id='1'> |
| ------------------------> |
| |
| <iq type='result' id='1'> |
| <------------------------ |
| |
| <iq type='set' id='2'> |
| ------------------------> |
| |
| <iq type='error' id='2'> |
| <------------------------ |
| |
In order to enforce these semantics, the following rules apply:
Stanza-related errors are handled in a manner similar to stream errors, except that hints are also provided to the receiving application regarding actions to take in response to the error.
The following rules apply to stanza-related errors:
The syntax for stanza-related errors is as follows:
<stanza-name to='sender' type='error'>
[RECOMMENDED to include sender XML here]
<error type='error-type'>
<defined-condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<text xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
OPTIONAL descriptive text
</text>
[OPTIONAL application-specific condition element]
</error>
</stanza-name>
The stanza-name is one of message, presence, or iq.
The value of the <error/> element's 'type' attribute MUST be one of the following:
The <error/> element:
The <text/> element is OPTIONAL. If included, it SHOULD be used only to provide descriptive or diagnostic information that supplements the meaning of a defined condition or application-specific condition. It SHOULD NOT be interpreted programmatically by an application. It SHOULD NOT be used as the error message presented to user, but MAY be shown in addition to the error message associated with the included condition element (or elements).
Note: the XML namespace name 'urn:ietf:params:xml:ns:xmpp-stanzas' that qualifies the descriptive element adheres to the format defined in The IETF XML Registry[23].
The following stanza-related error conditions are defined for use in stanza errors.
As noted, an application MAY provide application-specific stanza error information by including a properly-namespaced child in the error element. The application-specific element SHOULD supplement or further qualify a defined element. Thus the <error/> element will contain two or three child elements:
<iq type='error' id='some-id'>
<error type='modify'>
<bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<too-many-parameters xmlns='application-ns'/>
</error>
</iq>
<message type='error' id='another-id'>
<error type='modify'>
<undefined-condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<text xml:lang='en' xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
Some special application diagnostic information!
</text>
<special-application-condition xmlns='application-ns'/>
</error>
</message>
| TOC |
XMPP is a simplified and specialized protocol for streaming XML elements in order to exchange messages and presence information in close to real time. Because XMPP does not require the parsing of arbitrary and complete XML documents, there is no requirement that XMPP needs to support the full XML specification[1]. In particular, the following restrictions apply.
With regard to XML generation, an XMPP implementation MUST NOT inject into an XML stream any of the following:
With regard to XML processing, if an XMPP implementation receives such restricted XML data, it MUST ignore the data.
XML Namespaces[10] are used within all XMPP-compliant XML to create strict boundaries of data ownership. The basic function of namespaces is to separate different vocabularies of XML elements that are structurally mixed together. Ensuring that XMPP-compliant XML is namespace-aware enables any XML to be structurally mixed with any data element within XMPP. Rules for XML namespace names and prefixes are defined below.
A stream namespace declaration is REQUIRED in both XML stream headers. The name of the stream namespace MUST be 'http://etherx.jabber.org/streams'. The element names of the <stream/> element and its <features/> and <error/> children MUST be qualified by the stream namespace prefix in all instances. An implementation SHOULD generate only the 'stream:' prefix for these elements, and for historical reasons MAY accept only the 'stream:' prefix.
A default namespace declaration is REQUIRED and is used in both XML streams in order to define the allowable first-level children of the root stream element. This namespace declaration MUST be the same for the initiating stream and the responding stream so that both streams are qualified consistently. The default namespace declaration applies to the stream and all stanzas sent within a stream (unless explicitly qualified by another namespace, or by the prefix of the stream namespace or the dialback namespace).
A server implementation MUST support the following two default namespaces (for historical reasons, some implementations MAY support only these two default namespaces):
A client implementation MUST support the 'jabber:client' default namespace, and for historical reasons MAY support only that default namespace.
An implementation MUST NOT generate namespace prefixes for elements in the default namespace if the default namespace is 'jabber:client' or 'jabber:server'. An implementation SHOULD NOT generate namespace prefixes for elements qualified by content (as opposed to stream) namespaces other than 'jabber:client' and 'jabber:server'.
Note: the 'jabber:client' and 'jabber:server' namespaces are nearly identical but are used in different contexts (client-to-server communications for 'jabber:client' and server-to-server communications for 'jabber:server'). The only difference between the two is that the 'to' and 'from' attributes are OPTIONAL on stanzas sent within 'jabber:client', whereas they are REQUIRED on stanzas sent within 'jabber:server'. If a compliant implementation accepts a stream that is qualified by the 'jabber:client' or 'jabber:server' namespace, it MUST support the common attributes and basic semantics of all three core stanza kinds (message, presence, and IQ).
A dialback namespace declaration is REQUIRED for all elements used in server dialback. The name of the dialback namespace MUST be 'jabber:server:dialback'. All elements qualified by this namespace MUST be prefixed. An implementation SHOULD generate only the 'db:' prefix for such elements and MAY accept only the 'db:' prefix.
Except as noted with regard to 'to' and 'from' addresses for stanzas within the 'jabber:server' namespace, a server is not responsible for validating the XML elements forwarded to a client or another server; an implementation MAY choose to provide only validated data elements but is NOT REQUIRED to do so (although an implementation MUST NOT accept XML that is not well-formed). Clients SHOULD NOT rely on the ability to send data which does not conform to the schemas, and SHOULD ignore any non-conformant elements or attributes on the incoming XML stream. Validation of XML streams and stanzas is NOT REQUIRED or recommended, and schemas are included herein for descriptive purposes only.
Implementations SHOULD send a text declaration before sending a stream header. Applications MUST follow the rules in the XML specification[1] regarding the circumstances under which a text declaration is included.
Implementations MUST support the UTF-8 (RFC 2279[16]) transformation of Universal Character Set (ISO/IEC 10646-1[17]) characters, as required by RFC 2277[14]. Implementations MUST NOT attempt to use any other encoding.
| TOC |
A URN sub-namespace for TLS-related data in the Extensible Messaging and Presence Protocol (XMPP) is defined as follows.
- URI:
- urn:ietf:params:xml:ns:xmpp-tls
- Specification:
- [RFCXXXX]
- Description:
- This is the XML namespace name for TLS-related data in the Extensible Messaging and Presence Protocol (XMPP) as defined by [RFCXXXX].
- Registrant Contact:
- IETF, XMPP Working Group, <xmppwg@jabber.org>
A URN sub-namespace for SASL-related data in the Extensible Messaging and Presence Protocol (XMPP) is defined as follows.
- URI:
- urn:ietf:params:xml:ns:xmpp-sasl
- Specification:
- [RFCXXXX]
- Description:
- This is the XML namespace name for SASL-related data in the Extensible Messaging and Presence Protocol (XMPP) as defined by [RFCXXXX].
- Registrant Contact:
- IETF, XMPP Working Group, <xmppwg@jabber.org>
A URN sub-namespace for stream-related error data in the Extensible Messaging and Presence Protocol (XMPP) is defined as follows.
- URI:
- urn:ietf:params:xml:ns:xmpp-streams
- Specification:
- [RFCXXXX]
- Description:
- This is the XML namespace name for stream-related error data in the Extensible Messaging and Presence Protocol (XMPP) as defined by [RFCXXXX].
- Registrant Contact:
- IETF, XMPP Working Group, <xmppwg@jabber.org>
A URN sub-namespace for stanza-related error data in the Extensible Messaging and Presence Protocol (XMPP) is defined as follows. </