<abstract>This document defines a data format whereby basic information of an XMPP domain can be expressed and exposed over pub-sub.</abstract>
&LEGALNOTICE;
<number>xxxx</number>
<status>ProtoXEP</status>
<type>Standards Track</type>
<sig>Standards</sig>
<approver>Council</approver>
<dependencies/>
<supersedes/>
<supersededby/>
<shortname>serverinfo</shortname>
<author>
<firstname>Guus</firstname>
<surname>der Kinderen</surname>
<email>guus.der.kinderen@gmail.com</email>
<jid>guus.der.kinderen@igniterealtime.org</jid>
</author>
<revision>
<version>1.0.0</version>
<date>2023-12-19</date>
<initials>gdk</initials>
<remark>
<ul>
<li>Initial version.</li>
</ul>
</remark>
</revision>
</header>
<section1topic="Introduction"anchor="intro">
<p>To facilitate discovery of information of individual domains in an XMPP-based network, this specification defines a data format to define basic information for individual XMPP domains. By leveraging &xep0060; this information can efficiently be shared with applications that compose an overview of the larger XMPP network.</p>
<li>Describe links between nodes in an XMPP-based network, by enumerating connections used for federation between XMPP domains.</li>
<li>An extensible data format, allowing additional data (such as that defined in &xep0092;) to be retrievable without requiring additional round-trips.</li>
<p>Domains supporting the publication of Server Information data, as described in this document, MUST advertise the fact by announcing a &xep0030; feature of 'urn:xmpp:serverinfo:0'. This signifies that an administrative entity approved the publication of data, which is important for the opt-in mechanism described in <linkurl="#privacy">Privacy Considerations section</link> of this document.</p>
<p>The pub-sub service address and node in which Server Information data is advertised SHOULD be specified using a &xep0128;. These pub-sub coordinates MUST be scoped using a FORM_TYPE of "http://jabber.org/network/serverinfo" (as already specified in XEP-0128) and data form fields registered for this purpose as defined in the <linkurl="#registrar">XMPP Registrar Considerations section</link> of this document.</p>
<p>When the 'urn:xmpp:serverinfo:0' feature but no corresponding Service Discovery Extension is advertised, the node that is used will be a first-level leaf node using the name 'serverinfo' on the first pub-sub service advertised through service discovery.</p>
<examplecaption="Service Discovery information request"><![CDATA[
<p>The data format uses an element named 'serverinfo' in the namespace 'urn:xmpp:serverinfo:0'. In its minimal form, it defines each XMPP domain name served by the local server in an attribute named 'name'.</p>
<p>The optional 'federation' child element is used to denote remote XMPP domains with which the local domain is federating. Each of them are represented by an element named 'remote-domain'. The domain name of the peer in an optional attribute named 'name'. Optionally, each actual (e.g. TCP) connection from the local server to the peer is added as a 'connection' child-element to the 'remote-domain' element, that has an optional 'type' attribute, defining the directionality of the connection (one of 'incoming', 'outgoing' and 'bidi').</p>
<p>The name of a remote domain MUST only be included if the remote server advertises supporting for this XEP. This acts as an opt-in mechanism, to address the privacy concern defined in the <linkurl="#privacy">Privacy Considerations section</link> of this document.</p>
<p>Additional data MAY be included as child-elements of the 'serverinfo' element or any of the 'domain' elements. Such data MUST be namespaced appropriately. The example below uses the 'query' element defined in &xep0092; to include information about the software application associated with the local server.</p>
<p>The data is to be published using a pub-sub node named 'serverinfo' that MUST be a first-level leaf node of a pub-sub service for the domain. It is RECOMMENDED that the leaf-node is configured to have an open access model and contain a maximum of 1 item.</p>
<p>As certain information can be expected to be updated continuously and frequently, the server MAY choose to reduce the frequency of updates of the 'serverinfo' pub-sub node.</p>
<p>When multiple domains publish their connections to named remote domains, an information leak occurs: by collecting these public statistics, behavioral data of those remote domains can be deduced. To prevent undesired privacy-sensitive information leaks, a domain MUST NOT publish the name of a remote domain, unless that domain advertises support for this XEP, as defined in the <linkurl="#disco">Discovering Support section</link> of this document.</p>
<p>This way, the service discovery mechanism doubles as an opt-in mechanism. Domains that advertise support for this XEP allow other domains to reference them by domain-name in the data that they publish. The mere presence of an applicable pub-sub node MUST NOT be used for Service Discovery purposes, as under common service configuration, non-administrative users are allowed to create such nodes.</p>
<p>Upon advancement of this specification from a status of Experimental to a status of Draft, the ®ISTRAR; shall include the following information in its registries.</p>
<p>&xep0068; defines a process for standardizing the fields used within Data Forms qualified by a particular namespace, and <cite>XEP-0128</cite> describes how to use field standardization in the context of service discovery. This section registers fields for server information scoped by the "http://jabber.org/network/serverinfo" FORM_TYPE.</p>
<codecaption='Registry Submission'><![CDATA[
<form_type>
<name>http://jabber.org/network/serverinfo</name>
<doc>XEP-0XXX</doc>
<desc>
Forms advertising the coordinates of a pub-sub service and node for publication of Server Information data.
</desc>
<field
var='serverinfo-pubsub-service'
type='list-multi'
label='The address of a pub-sub service that hosts a node on which Server Information data is published.'/>
<field
var='serverinfo-pubsub-node'
type='list-multi'
label='A nodeId on which Server Information data is published.'/>
</form_type>
]]></code>
<p>Note that the FORM_TYPE used by &xep0157; is purposefully re-used by this XEP, to circumvent the restriction of having at most one XMPP Standards Foundation defined FORM_TYPE for a service discovery identity, as defined in &xep0128;. When a service supports both features, the data in both forms SHOULD be merged into one form.</p>
<p>Inspiration was taken from the (now defunct) 'server info' crawler by Thomas Leister. Many thanks to Dave Cridland, as well as 'zoidberg' and 'chewie' from the Ignite Realtime community for helping to test the initial implementation of a graphing implementation based on this XEP and to Florian Schmaus, Matthew Wild, Jonas Schäfer and Kevin Smith for their feedback on the earliest drafts of this document.</p>
