This extension allows XMPP servers to dispatch incoming and outgonig messages to all connected resources of an XMPP entity. This allows all devices of a user to be aware of chats which are happening or happened on other devices of that user.
The server returns a stream header to the client along with stream features, where the features include an <mr2/> element qualified by the 'urn:xmpp:mr2:0' namespace (see Namespace Versioning regarding the possibility of incrementing the version number).
S: <stream:stream
from='example.com'
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
version='1.0'>
S: <stream:features>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/>
<mr2 xmlns='urn:xmpp:mr2:0'/>
</stream:features>To enable use of message routing 2.0, the client sends an <enable/> nonza to the server.
C: <enable xmlns='urn:xmpp:mr2:0'/>
Upon receiving the enable request, the server MUST reply with an <enabled/> nonza or a <failed/> nonza qualified by the 'urn:xmpp:mr2:0' namespace. The <failed/> element indicates that there was a problem creating a message routing 2.0 enabled stream. The <enabled/> nonza indicates successful creation of a message routing 2.0 enabled stream.
S: <enabled xmlns='urn:xmpp:mr2:0'/>
TODO: Now the server MUST use MR2.
The client MUST NOT attempt to negotiate message routing 2.0 until it is authenticated; i.e., it MUST NOT send an <enable/> element until after authentication (such as SASL, Non-SASL Authentication (XEP-0078) [1] or Server Dialback (XEP-0220) [2]) has been completed successfully. the client MUST enable message routing 2.0 before it has completed Resource Binding.
The server SHALL enforce this order and return a <failed/> element in response if the order is violated (see Error Handling).
S: <failed xmlns='urn:xmpp:mr2:0'>
<unexpected-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</failed>When the server receives a <message/> that is not of type "groupchat" or "error" to a bare JID (localpart@domainpart), it delivers a copy to each resource using a Message Routing 2.0 enabled XMPP stream for the bare JID – in addition to delivering according to RFC 6121 § 8.5.2. This process is sometimes called "forking".
<message xmlns='jabber:client'
from='juliet@capulet.example/balcony'
to='romeo@montague.example'
type='chat'>
<body>Wherefore art thou, Romeo?</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>
<message xmlns='jabber:client'
from='juliet@capulet.example/balcony'
to='romeo@montague.example/garden'
type='chat'>
<body>Wherefore art thou, Romeo?</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>
<message xmlns='jabber:client'
from='juliet@capulet.example/balcony'
to='romeo@montague.example/home'
type='chat'>
<body>Wherefore art thou, Romeo?</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>The receiving server MUST deliver a copy to every Message Routing 2.0-enabled resource, even if that resource normally would not receive <message/> stanzas addressed to the bare JID (e.g., resources which have broadcast <presence/> with a negative priority). A Message Routing 2.0-enabled resource MUST NOT receive more than one copy of the <message/>.
When the server receives a <message/> of type "chat" addressed to a full JID (localpart@domainpart/resourcepart), it delivers the <message/> according to RFC 6121 § 8.5.3, and delivers a forwarded copy to each Message Routing 2.0-enabled resource for the matching bare JID recipient.
Each forwarded copy is wrapped using Stanza Forwarding (XEP-0297) [3]. The wrapping message SHOULD maintain the same 'type' attribute value; the 'from' attribute MUST be the Message Routing 2.0-enabled user's bare JID (e.g., "localpart@domainpart"); and the 'to' attribute MUST be the full JID of the resource receiving the copy. The content of the wrapping message MUST contain a <received/> element qualified by the namespace "urn:xmpp:mr2:0", which itself contains a <forwarded/> element qualified by the namespace "urn:xmpp:forward:0" that contains the original <message/>.
<message xmlns='jabber:client'
from='juliet@capulet.example/balcony'
to='romeo@montague.example/garden'
type='chat'>
<body>What man art thou that, thus bescreen'd in night, so stumblest on my counsel?</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>
<message xmlns='jabber:client'
from='romeo@montague.example'
to='romeo@montague.example/home'
type='chat'>
<received xmlns='urn:xmpp:mr2:0'>
<forwarded xmlns='urn:xmpp:forward:0'>
<message xmlns='jabber:client'
from='juliet@capulet.example/balcony'
to='romeo@montague.example/garden'
type='chat'>
<body>What man art thou that, thus bescreen'd in night, so stumblest on my counsel?</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>
</forwarded>
</received>
</message>
The receiving server MUST NOT send a forwarded copy to the full JID the original <message/> stanza was addressed to, as that recipient receives the original <message/> stanza.
When a client sends a <message/> of type "chat", its sending server delivers the <message/> according to RFC 6120 and RFC 6121, and delivers a forwarded copy to each Message Routing 2.0-enabled resource for the matching bare JID sender.
Each forwarded copy is wrapped using Stanza Forwarding (XEP-0297) [3]. The wrapping message SHOULD maintain the same 'type' attribute value; the 'from' attribute MUST be the Message Routing 2.0-enabled user's bare JID (e.g., "localpart@domainpart"); and the 'to' attribute SHOULD be the full JID of the resource receiving the copy. The content of the wrapping message MUST contain a <sent/> element qualified by the namespace "urn:xmpp:mr2:0", which itself contains a <forwarded/> qualified by the namespace "urn:xmpp:forward:0" that contains the original <message/> stanza.
<message xmlns='jabber:client'
from='romeo@montague.example/home'
to='juliet@capulet.example/balcony'
type='chat'>
<body>Neither, fair saint, if either thee dislike.</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>
<message xmlns='jabber:client'
from='romeo@montague.example'
to='romeo@montague.example/garden'
type='chat'>
<sent xmlns='urn:xmpp:mr2:0'>
<forwarded xmlns='urn:xmpp:forward:0'>
<message xmlns='jabber:client'
to='juliet@capulet.example/balcony'
from='romeo@montague.example/home'
type='chat'>
<body>Neither, fair saint, if either thee dislike.</body>
<thread>0e3141cd80894871a68e6fe6b1ec56fa</thread>
</message>
</forwarded>
</sent>
</message>The sending server SHOULD NOT send a forwarded copy to the sending full JID if it is a Message Routing 2.0-enabled resource.
Unlike carbons:
The Message Routing 2.0 state is kept if the stream is resumed by means of Stream Management (XEP-0198) [4]. That is, clients are not required to enable Message Routing 2.0 if the stream is resumed. They MUST however, enable Message Routing 2.0 if stream resumption failed and they wish to use Message Routing 2.0.
TODO should Client State Indication (XEP-0352) [5] delay certain forked messages, e.g. the onces caused by a message send to a full JID?
Note that Chat State Notifications (XEP-0085) [6] recommends sending chat state notifications as chat type messages, which means that they will be subject to MR2-copying. This is intentional.
Additionally, there are other considerations for clients that implement MR2s and XEP-0085:
When a receiving server attempts to deliver a forked message, and that message bounces with an error for any reason, the receiving server MUST NOT forward that error back to the original sender. The receiving server SHOULD use the sent element in the bounce to determine that an error is from a forked message.
This rule is used to prevent some of the half-failure modes that have been an issue in other prototocols.
Clients that automatically respond to messages for any reason (e.g., when in the "dnd" presence show state) MUST take adequate care when enabling MR2s in order to prevent storms or loops. MR2 copies of messages MUST NOT be auto-replied to under any circumstances. Forked inbound messages MUST NOT be auto-replied to unless the client has some way of ensuring no more than one auto-reply is sent from all of its user's resources.
Enabling this protocol on mobile devices needs to be undertaken with care. This protocol can result in additional bandwidth and power usage, possibly decreasing battery lifetime and increasing monetary costs. Additional mechanisms for controlling the MR2-copying or forking of individual conversations might need to be added to deal with mobile clients in the future.
As the notifications defined in this document contain full <message/> stanzas, it is important for implementations to take care that the receiving entities of such notifications are allowed to see that information. This usually means they receiving entities share the same bare JID with the intended receiver. (TODO wording)
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [7].
The XMPP Registrar [8] includes 'urn:xmpp:mr2:0' in its registry of protocol namespaces (see <https://xmpp.org/registrar/namespaces.html>).
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.
REQUIRED for protocol specifications.
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This XMPP Extension Protocol is copyright (c) 1999 - 2014 by the XMPP Standards Foundation (XSF).
Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.
## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##
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This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).
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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-0078: Non-SASL Authentication <https://xmpp.org/extensions/xep-0078.html>.
2. XEP-0220: Server Dialback <https://xmpp.org/extensions/xep-0220.html>.
3. XEP-0297: Stanza Forwarding <https://xmpp.org/extensions/xep-0297.html>.
4. XEP-0198: Stream Management <https://xmpp.org/extensions/xep-0198.html>.
5. XEP-0352: Client State Indication <https://xmpp.org/extensions/xep-0352.html>.
6. XEP-0085: Chat State Notifications <https://xmpp.org/extensions/xep-0085.html>.
7. 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/>.
8. 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/>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
First draft.
END