WARNING: This Standards-Track document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems are advised to carefully consider whether it is appropriate to deploy implementations of this protocol before it advances to a status of Draft.
The XMPP Network is a network of servers which each have their own administration policies, status reports, and other peculiarities. Contact Addresses for XMPP Services (XEP-0157)  provides a consistent framework for reaching out to administrators and reporting abuse, incidents, or even giving feedback on the service, and the goal of this specification is to provide a similar framework for letting users (or other entities) know the server status in-band or out of band (in case of hard failures).
Centralized systems usually control both the infrastructure and client code, making it easy to hardcode information retrieval one way or the other.
The usual way of informing users of planned maintenance, partial or total outage was previously through "announce" modules that lets the admin broadcast server-wided messages. This approach has several drawbacks, as it will appear in most clients as a new discussion with the server JID, which can prove confusing. It also does not provide a way to reach the user when the XMPP server is offline.
To make such discovery possible, we specify a Service Discovery Extensions (XEP-0128)  mechanism that a server SHOULD return in response to service discovery information ("disco#info") requests sent to the bare domain of the server. This information MUST be scoped using a FORM_TYPE of "urn:xmpp:sos:0" (as already specified in XEP-0128) and data form fields registered for this purpose as defined in the XMPP Registrar Considerations section of this document.
Values of 'external-status-addresses' form field MUST be valid URIs, i.e. comply with the 'xs:anyURI' datatype of XML Schema Part 2 .
Links present inside the 'external-status-addresses' field SHOULD use HTTP/HTTPS protocol and the resources referenced MUST be available without authentication.
TODO: do we want this to be XML or json? I have no real preference, in any case it should be preferably generated by a tool but easy to write by hand, as this needs to be usable in situations where time is the essence.
The format used for the external status is defined here, to allow a wide range
of compatibility across services and clients.
A client MUST ignore unknown extra fields present in the JSON file, to allow extensibility, and implementations MAY add other fields.
The "message" field MUST contain at least a message on the "default" key, that will be
used by the client if the current user language is not found. It is left to the
operator to determine which language is more relevant as a default, according to the
server’s user base.
When the outage is over, the file SHOULD be replaced with an empty JSON object.
The following JSON schema is provided as a means to describe and validate the
file exposed by the external service:
Entities from other servers MAY be allowed to subscribe to other server nodes, to allow external services
to monitor the server. Doing so allows aggregation of XMPP outage events across the network, for a better
A client implementing this extension MUST fetch the addresses of the external service and cache it
for later use. Doing so allows the client to use this information when it is impossible to connect
to the server.
A client receiving an outage event for a time in the future SHOULD treat it as a planned event
that is not already happening and adapt its display consequently.
When connected, a client SHOULD NOT fetch the external file as the in-band notification provides
the same information, if available.
Both the JSON and the XML format defined in this document allow for internationalization in the fields that are expected to be presented to the user as-is. The other fields are machine-readable and their various values SHOULD be translated in the implementing applications.
Client implementations MUST check the provenance of the pubsub notifications before displaying a notification, otherwise malicious entities could send fake outage events.
Server administrators MUST ensure the servers provided in 'external-status-addresses' are trusted, as malicious administrators of this server could use the referenced file
to display arbitrary messages to users.
Field Standardization for Data Forms (XEP-0068)  defines a process for standardizing the fields used within Data Forms qualified by a particular namespace, and XEP-0128 describes how to use field standardization in the context of service discovery. This section registers fields for server information scoped by the "urn:xmpp:sos:0" FORM_TYPE.
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).
The HTML representation (you are looking at) is maintained by the XSF. It is based on the YAML CSS Framework, which is licensed under the terms of the CC-BY-SA 2.0 license.
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".
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/>.