WARNING: This document has been automatically Deferred after 12 months of inactivity in its previous Experimental state. Implementation of the protocol described herein is not recommended for production systems. However, exploratory implementations are encouraged to resume the standards process.
This document is one of several proposals for distributing XMPP chat rooms across multiple chat services. It is expected that the various approaches will be refined and harmonized before a final protocol is developed.
The architecture is that of a single root node, called PRIMARY and several repeater nodes, each called REPLICA. Every stanza is submitted via the replicas to the primary, control is centralized there. The primary then sends a copy of the stanza to each of the replicas where it is processed and then distributed to each of the replica's leaf nodes, local users at this point. During redistribution, the replica shall not change the stanza's 'from' attribute, which is only possible if the replica is in the same security domain as the user. The result of that is a decreased number of messages on the server-to-server links between the primary's server and each of the replica servers.
Note that this only applies to stanzas that are directed to all occupants, such as the change of availability status and messages whose 'type' attribute is set to 'groupchat'.
While 1-1 stanzas such as in-room private messages or vcard-temp requests may also travel along that path they are currently unaffected by this.
Most of the examples in this document use the scenario of the 1990 war that split the Internet Relay Chat into several incompatible networks. The battlefield is represented here by the "email@example.com" chatroom. The characters are as follows:
In our example we are presuming that three replicas from three hosts have registered with the primary for traffic redistribution. They are doing so using replica@host jids, but they could be using any temporary jid the implementor finds useful to choose.
If a new occupant requests to enter the room, the primary first sends a presence update to all participants to inform them of the presence of the new user. Then, the primary sends the affected replica a stanza requesting it to add the user to the distribution list
The replica MUST verify that the user has sent directed presence to the primary's JID before. This helps to ensure that the user intended to enter the room. If this is ture, the replica shall add the user to the distribution list and send the room roster, occupants own presence in room and discussion history to the full jid of the added user.
Presence updates are distributed by the primary to all replicas.
Note that the primary MUST NOT send the full jid of the user to any replicas without members that are moderators.
When rebroadcasting this stanza to its local occupants, the replica MUST remove the participants full JID subject to the rules of XEP-0045. In addition, the replica stores the resulting changes to the room roster, so that it can send the correct state to entering users.
When relaying a message, the primary SHOULD add a urn:xmpp:delay element inside dmuc element so that the replica can provide proper timestamps to new users. The primary then sends a copy of the stanza to each replica.
After saving the stanza for the purpose of keeping a room history, the replica SHOULD remove the urn:xmpp:tmp:dmuc:0 element and send the stanza to each local user.
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.
Disclaimer of Warranty
## 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. ##
Limitation of Liability
In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.
This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 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 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. 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/>.
2. 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/>.