mirror of
https://github.com/moparisthebest/xeps
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188 lines
7.9 KiB
XML
188 lines
7.9 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>Source-Specific Media Attributes in Jingle</title>
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<abstract>This specification provides an XML mapping for translating the RFC 5766 Source-Specific Media Attributes from SDP to Jingle</abstract>
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&LEGALNOTICE;
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<number>0339</number>
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<status>Draft</status>
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<lastcall>2020-05-19</lastcall>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<approver>Council</approver>
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<dependencies>
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<spec>XEP-0166</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>NOT_YET_ASSIGNED</shortname>
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&fippo;
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<revision>
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<version>1.0.0</version>
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<date>2020-05-26</date>
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<initials>XEP Editor (jsc)</initials>
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<remark><p>Move to Draft as per Council vote from 2020-05-20.</p></remark>
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</revision>
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<revision>
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<version>0.3</version>
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<date>2017-09-11</date>
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<initials>XEP Editor (jwi)</initials>
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<remark>Defer due to lack of activity.</remark>
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</revision>
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<revision>
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<version>0.2</version>
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<date>2015-11-09</date>
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<initials>ph</initials>
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<remark><p>remove obsolete mslabel and label lines.</p></remark>
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</revision>
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<revision>
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<version>0.1</version>
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<date>2014-01-08</date>
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<initials>psa</initials>
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<remark><p>Initial published version approved by the XMPP Council.</p></remark>
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</revision>
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<revision>
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<version>0.0.1</version>
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<date>2013-11-25</date>
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<initials>ph</initials>
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<remark><p>First draft.</p></remark>
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</revision>
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</header>
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<section1 topic="Introduction" anchor="intro">
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<p>&rfc5576; provides a mechanism to describe attributes of individual media sources (identified by their synchronization source) within a media stream. A mapping to Jingle as an extension to &xep0167; is defined in this document.</p>
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</section1>
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<section1 topic='Mapping to Session Description Protocol' anchor='sdp'>
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<section2 topic='The ssrc attribute' anchor='sdp-ssrc'>
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<p>The SDP format defined in <cite>RFC 5576</cite> is shown below.</p>
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<code>
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a=ssrc:<ssrc-id> <attribute>
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a=ssrc:<ssrc-id> <attribute>:<value>
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</code>
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<p>This maps to Jingle as a <source/> element qualified by the 'urn:xmpp:jingle:apps:rtp:ssma:0' namespace. Since 'ssrc' is a media attribute in SDP, the <source/> element is included as child of the Jingle <description/> element.</p>
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<code><![CDATA[
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<source ssrc='ssrc-id' xmlns='urn:xmpp:jingle:apps:rtp:ssma:0'>
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<parameter name='attribute'/>
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<parameter name='attribute' value='value'/>
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</source>
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]]></code>
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<p>Each ssrc-id maps to a <source/> element whose 'ssrc' attribute is set to the ssrc-id. The associated attributes map to <parameter/> children with 'name' and 'value' attributes. If there is no value in the SDP, the value parameter shall be omitted.</p>
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<p>An example follows:</p>
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<code>
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a=ssrc:1656081975 cname:Yv/wvbCdsDW2Prgd
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a=ssrc:1656081975 msid:MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIv MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIva0</code>
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<code><![CDATA[
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<source ssrc='1656081975' xmlns='urn:xmpp:jingle:apps:rtp:ssma:0'>
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<parameter name='cname' value='Yv/wvbCdsDW2Prgd'/>
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<parameter name='msid' value='MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIv MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIva0'/>
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</source>]]></code>
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</section2>
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<section2 topic='The ssrc-group attribute' anchor='sdp-ssrc-group'>
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<p>The SDP format defined in <cite>RFC 5576</cite> is shown below.</p>
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<code>
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a=ssrc-group:<semantics> <ssrc-id> ...</code>
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<p>This maps to Jingle as a <ssrc-group/> element qualified by the 'urn:xmpp:jingle:apps:rtp:ssma:0' namespace. Like the <source/> element, this is included as child of the Jingle <description/> element. The SDP 'semantics' parameter is mapped to the semantics attribute (for consistency with &xep0338;) and the list of ssrc-ids is mapped to <source/> elements whole 'ssrc' attribute is set to the ssrc-id.</p>
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<code><![CDATA[
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<ssrc-group xmlns='urn:xmpp:jingle:apps:rtp:ssma:0' semantics='semantics'>
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<source ssrc='ssrc-id'/>
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[...]
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</ssrc-group>]]></code>
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</section2>
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</section1>
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<section1 topic='Example' anchor='example'>
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<p>A minimal example follows:</p>
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<code>
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m=video 1 RTP/SAVPF 100 116 117
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a=rtpmap:100 VP8/90000
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a=ssrc-group:FID 2301230316 386328120
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a=ssrc:2301230316 cname:T5qvrIZj42v//eYQ
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a=ssrc:386328120 cname:uEYgNtStZyTF74sM
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a=ssrc-group:FID 3139499595 2613715171
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a=ssrc:3139499595 cname:re8jhxkly9bxzuxr
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a=ssrc:2613715171 cname:f83avsiw6n1m7vi
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</code>
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<p>This is mapped to Jingle as follows:</p>
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<code><![CDATA[
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<content creator='initiator' name='webcam'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
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<payload-type id='100' name='VP8' clockrate='90000'/>
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<ssrc-group xmlns='urn:xmpp:jingle:apps:rtp:ssma:0' semantics='FID'>
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<source ssrc='2301230316'/>
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<source ssrc='386328120'/>
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</ssrc-group>
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<ssrc-group xmlns='urn:xmpp:jingle:apps:rtp:ssma:0' semantics='FID'>
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<source ssrc='3139499595'/>
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<source ssrc='2613715171'/>
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</ssrc-group>
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<source ssrc='2301230316' xmlns='urn:xmpp:jingle:apps:rtp:ssma:0'>
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<parameter name='cname' value='T5qvrIZj42v//eYQ'/>
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</source>
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<source ssrc='386328120' xmlns='urn:xmpp:jingle:apps:rtp:ssma:0'>
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<parameter name='cname' value='uEYgNtStZyTF74sM'/>
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</source>
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<source ssrc='3139499595' xmlns='urn:xmpp:jingle:apps:rtp:ssma:0'>
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<parameter name='cname' value='re8jhxkly9bxzuxr'/>
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</source>
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<source ssrc='2613715171' xmlns='urn:xmpp:jingle:apps:rtp:ssma:0'>
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<parameter name='cname' value='f83avsiw6n1m7vi'/>
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</source>
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</description>
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</content>
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]]></code>
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</section1>
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<section1 topic='Determining Support' anchor='disco'>
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<p>If an entity supports source specific media attributes as described in <cite>RFC 5576</cite>, it MUST advertise that fact in its responses to &xep0030; information ("disco#info") requests by returning a feature of 'urn:ietf:rfc:5576':</p>
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<example caption='A disco#info query'><![CDATA[
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<iq type='get'
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from='calvin@usrobots.lit/lab'
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to='herbie@usrobots.lit/home'
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id='disco1'>
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<query xmlns='http://jabber.org/protocol/disco#info'/>
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</iq>
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]]></example>
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<example caption='A disco#info response'><![CDATA[
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<iq type='result'
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from='herbie@usrobots.lit/home'
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to='calvin@usrobots.lit/lab'
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id='disco1'>
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<query xmlns='http://jabber.org/protocol/disco#info'>
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<feature var='urn:xmpp:jingle:1'/>
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<feature var='urn:ietf:rfc:5576'/>
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</query>
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</iq>
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]]></example>
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<p>In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.</p>
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</section1>
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<!--
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<section1 topic='Acknowledgements' anchor='acks'>
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</section1>
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-->
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<section1 topic='Security Considerations' anchor='security'>
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<p>This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.</p>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>This document requires no interaction with &IANA;.</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<section2 topic='Protocol Namespaces' anchor='registrar-ns'>
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<p>This specification defines the following XML namespace:</p>
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<ul>
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<li>urn:xmpp:jingle:apps:rtp:ssma:0</li>
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</ul>
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<p>The ®ISTRAR; includes the foregoing namespace to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.</p>
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</section2>
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<section2 topic='Protocol Versioning' anchor='registrar-versioning'>
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&NSVER;
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</section2>
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</section1>
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<section1 topic='XML Schema' anchor='schema'>
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<p>TODO</p>
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</section1>
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</xep>
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