Jabber Component Protocol (XEP-0114) [1] defines a protocol that enables a server component to connect to an XMPP server. However, there are a number of perceived limitations with that protocol:
This document specifies a standards-track protocol that addresses the basic requirements for component connections. In the future, additional documents may specify more advanced features on top of the protocol defined herein.
This document addresses the following requirements:
XML streams are established between a component and a server exactly as they are between a client and a server as specified in XMPP Core [4], with the following exceptions:
The protocol defined in XEP-0114 depended on use of the 'to' address in the stream header to specify the hostname of the component. By contrast, client-to-server connections use stream establishment is followed by binding of a resource to the stream (in fact multiple resources can be bound to the stream). This protocol emulates client-to-server connections by using a hostname binding process that is similar to the resource binding process specified in XMPP Core.
If a server offers component binding over a stream, it MUST advertise a feature of "urn:xmpp:component:0".
S: <stream:stream
from='example.com'
id='gPybzaOzBmaADgxKXu9UClbprp0='
to='chat.example.com'
version='1.0'
xml:lang='en'
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'>
S: <stream:features>
<bind xmlns='urn:xmpp:component:0'>
<required/>
</bind>
</stream:features>
In order to bind a hostname, the component sends a bind request to the server.
C: <iq id='bind_1' type='set'>
<bind xmlns='urn:xmpp:component:0'>
<hostname>chat.example.com</hostname>
</bind>
</iq>
If the hostname can be bound, the server MUST return an IQ-result specifying the exact hostname that was bound.
S: <iq id='bind_1' type='result'>
<bind xmlns='urn:xmpp:component:0'>
<hostname>chat.example.com</hostname>
</bind>
</iq>
If the hostname cannot be bound, the server MUST return an IQ-error, which SHOULD be <bad-request/>, <conflict/>, <not-allowed/>, or <resource-constraint/>, just as with client resource binding as specified in RFC 3920.
Note: Although the JID asserted during STARTTLS and SASL negotiation MUST be of the form <domain> (i.e., an XMPP domain identifier), the <hostname/> element MAY be of the form <domain/resource>. This form can be used for application-specific functionality (e.g., load balancing), but such functionality is out of scope for this specification.
A component can send a subsequent bind request to bind another hostname (a server MUST support binding of multiple hostnames).
C: <iq id='bind_2' type='set'>
<bind xmlns='urn:xmpp:component:0'>
<hostname>foo.example.com</hostname>
</bind>
</iq>
If the server cannot process the bind request (e.g., because the component has already bound the desired hostname), the server MUST return an IQ-error (e.g., <conflict/>).
A component can also unbind a resource that has already been bound (a server MUST support unbinding).
C: <iq id='unbind_1' type='set'>
<unbind xmlns='urn:xmpp:component:0'>
<hostname>foo.example.com</hostname>
</unbind>
</iq>
If the hostname can be unbound, the server MUST return an IQ-result.
S: <iq id='unbind_1' type='result'/>
This protocol improves upon the earlier component protocol defined in XEP-0114 by specifying the use of Transport Layer Security (TLS) for channel encryption and the Simple Authentication and Security Layer (SASL) for authentication. Because this protocol re-uses the XML stream establishment processes defined in XMPP Core, the security considerations from RFC 3920 and RFC 6120 apply to this protocol as well.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [5].
This specification defines the following XML namespace:
Upon advancement of this specification from a status of Experimental to a status of Draft, the XMPP Registrar [6] shall add the foregoing namespace to the registry located at <https://xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function (XEP-0053) [7].
If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:xmpp:component:0'
xmlns='urn:xmpp:component:0'
elementFormDefault='qualified'>
<xs:element name='bind'>
<xs:complexType>
<xs:sequence>
<xs:choice minOccurs='0' maxOccurs='1'>
<xs:element name='hostname' type='xs:string'/>
</xs:choice>
<xs:element name='required'
minOccurs='0'
maxOccurs='1'
type='empty'/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name='unbind'>
<xs:complexType>
<xs:sequence minOccurs='0'>
<xs:element name='hostname' type='xs:string'/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
This document in other formats: XML PDF
This XMPP Extension Protocol is copyright © 1999 – 2020 by the XMPP Standards Foundation (XSF).
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.
Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.
Errata can be sent to <editor@xmpp.org>.
The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
1. XEP-0114: Jabber Component Protocol <https://xmpp.org/extensions/xep-0114.html>.
2. RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2 <http://tools.ietf.org/html/rfc5246>.
3. RFC 4422: Simple Authentication and Security Layer (SASL) <http://tools.ietf.org/html/rfc4422>.
4. RFC 6120: Extensible Messaging and Presence Protocol (XMPP): Core <http://tools.ietf.org/html/rfc6120>.
5. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
6. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.
7. XEP-0053: XMPP Registrar Function <https://xmpp.org/extensions/xep-0053.html>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
Modified namespace to incorporate namespace versioning; clarified that the value of the <hostname/> element can be either <domain> or <domain/resource>.
Initial published version.
First draft.
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