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<?xml version='1.0' encoding='UTF-8'?>
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
<header>
<title>Clique - link-local chat rooms</title>
<abstract>A protocol for serverless link-local multi-user chat over
reliable multicast.</abstract>
<legal>Copyright (c) 2007 Collabora Limited. This document may be
distributed under the same terms as the Telepathy specification.</legal>
<number>proto-clique</number>
<status>ProtoXEP</status>
<type>Extension</type>
<sig>Standards</sig>
<approver>Telepathy project</approver>
<dependencies>
<spec>XMPP Core</spec>
<spec>XEP-0174</spec>
</dependencies>
<supersedes/>
<supersededby/>
<shortname>NOT YET ASSIGNED</shortname>
<author>
<firstname>Simon</firstname>
<surname>McVittie</surname>
<email>simon.mcvittie@collabora.co.uk</email>
<jid>simon.mcvittie@collabora.co.uk</jid>
</author>
<revision>
<version>0.0.1</version>
<date>2007-11-02</date>
<initials>smcv</initials>
<remark><p>First draft.</p></remark>
</revision>
</header>
<section1 topic='Introduction' anchor='intro'>
<p>Clique is an extension of XEP-0174 to support multi-user chat.
It consists of the following components:</p>
<ul>
<li>a binary multicast message-passing protocol sometimes referred to
as rMulticast, with retransmission/reliability,
fragmentation/reassembly, causal ordering, and reliable membership
semantics, in which messages are associated with a stream ID in the
range 0 to 65535</li>
<li>XMPP-like XML messages sent with stream ID 0</li>
<li>optional auxiliary data (e.g. Tubes) sent with stream IDs
1-65535, with semantics signalled by XML messages in stream 0</li>
</ul>
<p>The chat room behaves a lot like XMPP, and namespaces used in XMPP
have their usual semantics. However, instead of a stream of XML
as in XMPP, Clique's XMPP-like messages are individually well-formed
XML documents.</p>
<p>XEP-0174 instance names are used for identification in a chat
room.</p>
<p>The Clique XML namespace can also be used for certain elements sent
over XEP-0174 unicast TCP streams, for instance to send invitations.</p>
</section1>
<section1 topic='Requirements' anchor='reqs'>
<p>STRONGLY RECOMMENDED.</p>
</section1>
<section1 topic='Glossary' anchor='glossary'>
<p>OPTIONAL.</p>
</section1>
<section1 topic='Use Cases' anchor='usecases'>
<p>FIXME: there need to be some examples of the actual Clique protocol
here</p>
<section2 topic='Advertising a public link-local chatroom via mDNS'>
<p>In this example a chatroom called "Witchcraft" uses the multicast
group 239.255.71.66, port 13251 (arbitrarily chosen).</p>
<p>We recommend that chatrooms use a random high port number
in a random multicast group in the range 239.255.71.x.</p>
<code>
<![CDATA[
; A dummy A record for the chatroom's multicast group
Witchcraft._clique._udp.local. IN A 239.255.71.66
; A DNS-SD service of type _clique._udp
_clique._udp.local. IN PTR Witchcraft._clique._udp.local.
Witchcraft._clique._udp.local. IN SRV 13251 ._clique._udp.local.
; For future expansion - implementations SHOULD NOT resolve this,
; unless they implement a future version of this protocol that
; defines some TXT keys for _clique._udp
Witchcraft._clique._udp.local. IN TXT "txtvers=0"
]]>
</code>
</section2>
<section2 topic='Inviting a contact to a public or private room'>
<p>In this example crone@desktop invites hecate@broom to the
chatroom given above.</p>
<p>This would work just as well if the chatroom was not advertised
in mDNS; this can be used to make "private" chatrooms. Note however
that anyone with a network traffic sniffer can see the chatroom
itself.</p>
<code>
<![CDATA[
<!-- Sent via XEP-0174 unicast TCP from crone@desktop to
hecate@broom -->
<message from='crone@desktop' to='hecate@broom'>
<invite xmlns='http://telepathy.freedesktop.org/xmpp/clique'>
<roomname>Witchcraft</roomname>
<address>239.255.71.66</address>
<port>13251</port>
<!-- reason is optional -->
<reason>We need to plot Macbeth's doom, but the XMPP server is
down</reason>
</invite>
<!-- Displayed by iChat and other non-Clique-compatible clients -->
<body>You got a Clique chatroom invitation</body>
</message>
]]>
</code>
</section2>
</section1>
<section1 topic='Business Rules' anchor='rules'>
<p>OPTIONAL.</p>
</section1>
<section1 topic='Implementation Notes' anchor='impl'>
<p>OPTIONAL.</p>
</section1>
<section1 topic='Internationalization Considerations' anchor='i18n'>
<p>OPTIONAL.</p>
</section1>
<section1 topic='Security Considerations' anchor='security'>
<p>REQUIRED.</p>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
<p>REQUIRED.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
<p>None.</p>
</section1>
<section1 topic='XML Schema' anchor='schema'>
<code>
<![CDATA[
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://telepathy.freedesktop.org/xmpp/clique'
xmlns='http://telepathy.freedesktop.org/xmpp/clique'
elementFormDefault='qualified'>
<!-- LLMUC invitation. Sent over the IM socket -->
<xs:element name='invite'>
<xs:complexType>
<xs:all>
<xs:element name='roomname' type='xs:string'/>
<xs:element name='reason' minOccurs='0' type='xs:string'/>
<xs:element name='address' type='xs:string'/>
<xs:element name='port' type='xs:unsignedShort'/>
<!-- In OLPC builds, <properties> with NS_OLPC_ACTIVITY_PROPS
goes here -->
<xs:any minOccurs='0' maxOccurs='unbounded' namespace='##other'>
</xs:all>
</xs:complexType>
</xs:element>
</xs:schema>
]]>
</code>
</section1>
</xep>
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