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429 lines
14 KiB
XML
429 lines
14 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>Stream Initiation</title>
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<abstract>A common method to initiate a stream with meta information</abstract>
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&LEGALNOTICE;
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<number>0087</number>
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<status>Retracted</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<dependencies>XEP-0030</dependencies>
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<supersedes>None</supersedes>
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<supersededby>XEP-0095</supersededby>
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<shortname>si</shortname>
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<author>
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<firstname>Thomas</firstname>
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<surname>Muldowney</surname>
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<email>temas@jabber.org</email>
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<jid>temas@jabber.org</jid>
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</author>
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<revision>
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<version>0.1</version>
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<date>2003-05-22</date>
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<initials>tjm</initials>
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<remark>Initial version.</remark>
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</revision>
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</header>
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<section1 topic='Introduction'>
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<p>
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As more people begin to make use of streams in Jabber, there becomes a need
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for more descriptive negotiation of which stream to use. This document provides
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a method to negotiate a stream and provide some meta-information about the
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streams usage.
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</p>
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</section1>
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<section1 topic='Requirements'>
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<ul>
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<li>
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The defined protocol will allow for negotiation of a common stream.
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</li>
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<li>
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The defined protocol will allow for meta-information to be sent about the
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stream usage.
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</li>
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<li>
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The defined protocol will not be required for stream usage.
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</li>
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</ul>
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<section2 topic='Use Case'>
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<p>
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Sender wishes to interact with another user, using a method that requires
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streams.
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</p>
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<p>
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Primary Flow:
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</p>
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<ol>
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<li>
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Sender discovers if Receiver implements the desired profile. [E1]
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</li>
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<li>
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Sender offers a stream initiation. [E2]
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</li>
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<li>
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Receiver accepts stream initiation.
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</li>
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<li>
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Sender uses the negotiated stream and profile to send the information.
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</li>
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</ol>
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<p>
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Error Conditions:
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</p>
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<ol>
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<li>
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The Receiver does not support the desired profile, EUC
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</li>
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<li>
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Receiver rejects the stream initiation, EUC
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</li>
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</ol>
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</section2>
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</section1>
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<section1 topic='Basic Usage'>
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<p>
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Before a Stream Initiation is attempted the Sender should be sure that the
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Receiver supports both Stream Initiation and the specific profile that they
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wish to use. This is discovered by using &xep0030;:
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</p>
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<example caption='Requesting Disco Information From Receiver'>
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<![CDATA[
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<iq
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type='get'
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to='receiver@jabber.org/resource'
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from='sender@jabber.org/resource'
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id='info1'>
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<query xmlns='http://jabber.org/protocol/disco#info'/>
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</iq>
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]]>
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</example>
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<p>
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The Receiver will advertise the "http://jabber.org/protocol/si" namespace as
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a feature to represent they implement this document. The specific profiles can
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be found by looking for
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"http://jabber.org/protocol/si/profile/profile-name". Shown in the result
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is a potential file transfer profile:
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</p>
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<example caption='Receiver Disco Information Result'>
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<![CDATA[
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<iq
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type='result'
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to='sender@jabber.org/resource'
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from='receiver@jabber.org/resource'
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id='info1'>
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<query xmlns='http://jabber.org/protocol/disco#info'>
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<feature var='http://jabber.org/protocol/si'/>
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<feature var='htpt://jabber.org/protocol/si/profile/filexfer'/>
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</query>
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</iq>
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]]>
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</example>
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<p>
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Now that the Sender is sure that the Receiver support Stream Initiation they
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send the offer:
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</p>
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<example caption='Offer Stream Initiation'>
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<![CDATA[
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<iq type='set' id='offer1' to='receiver@jabber.org/resource'>
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<si
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xmlns='http://jabber.org/protocol/si'
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id='a0'
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mime-type='application/octet-stream'
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profile='http://jabber.org/protocol/si/profile/profile-name'>
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<header name='key'>value</header>
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<feature xmlns='http://jabber.org/protocol/feature-neg'>
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<x xmlns='jabber:x:data'>
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<field var='file-transfer-method' type='list-single'>
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<option><value>s5b</value></option>
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<option><value>jabber:iq:oob</value></option>
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<option><value>ibb</value></option>
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</field>
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</x>
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</feature>
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</si>
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</iq>
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]]>
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</example>
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<!--
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<example caption='Offer Stream Initiation (Profile in NS)'>
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<![CDATA[
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<iq type='set' id='offer1' to='receiver@jabber.org/resource'>
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<si
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xmlns='http://jabber.org/protocol/si'
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id='a0'
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mime-type='application/octet-stream'>
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<profile xmlns='http://jabber.org/protocol/si/profile/profile-name'>
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<foo>
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<bar>baz</bar>
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</foo>
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</profile>
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<feature xmlns='http://jabber.org/protocol/feature-neg'>
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<x xmlns='jabber:x:data'>
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<field var='file-transfer-method' type='list-single'>
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<option><value>s5b</value></option>
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<option><value>jabber:iq:oob</value></option>
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<option><value>ibb</value></option>
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</field>
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</x>
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</feature>
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</si>
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</iq>
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]]>
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</example>
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-->
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<!--
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<example caption='Offer Regular File Transfer (Alternate Stream Negotiation)'>
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<![CDATA[
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<si
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xmlns='http://jabber.org/protocol/si'
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id='a0'
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mime-type='application/octet-stream'
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profile='filexfer'>
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<header name='size'>37678</header>
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<header name='hash'>a9234abbff332</header>
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<header name='name'>filename.txt</header>
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<stream>s5b</stream>
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<stream>jabber:iq:oob</stream>
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<stream>ibb</stream>
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</si>
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]]>
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</example>
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-->
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<p>
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At this point the Receiver can view the headers and other information to
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decide if they wish to accept the Stream Initiation. If they accept they
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MUST select one of the presented stream types to use. If none of the stream
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types are acceptable the Receiver MUST reply with an error:
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</p>
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<example caption='Accept Stream Initiation'>
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<![CDATA[
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<iq type='result' to='sender@jabber.org/resource' id='offer1'>
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<si
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xmlns='http://jabber.org/si'
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id='a0'>
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<feature xmlns='http://jabber.org/protocol/feature-neg'>
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<x xmlns='jabber:x:data' type='submit'>
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<field var='file-transfer-method'>
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<value>s5b</value>
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</field>
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</x>
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</feature>
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</si>
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</iq>
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]]>
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</example>
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<example caption='Rejecting Stream Initiation'>
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<![CDATA[
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<iq type='error' to='sender@jabber.org/resource' id='offer1'>
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<error code='403'>Offer Declined</error>
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</iq>
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]]>
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</example>
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<example caption='No Valid Streams'>
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<![CDATA[
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<iq type='error' to='sender@jabber.org/resource' id='offer1'>
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<error code='406'>No Valid Streams</error>
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</iq>
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]]>
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</example>
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<p>
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If the Receiver has accepted the Stream Initiation the Sender may then used
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the semantics defined by the selected stream and start the usage.
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</p>
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<!--
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<example caption='Accept File Transfer (Alternate Stream Negotiation)'>
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<![CDATA[
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<si
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xmlns='http://jabber.org/protocol/si'
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id='a0'>
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<stream>s5b</stream>
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</si>
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]]>
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</example>
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<example caption='Offer to Start a MP3 Stream'>
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<![CDATA[
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<si
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xmlns='http://jabber.org/protocol/si'
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id='s0'
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mime-type='audio/x-mp3'
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profile='streaming-audio'>
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<feature xmlns='http://jabber.org/protocol/feature-neg'>
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<x xmlns='jabber:x:data'>
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<field var='file-transfer-method' type='list-single'>
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<option><value>s5b</value></option>
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<option><value>ibb</value></option>
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</field>
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</x>
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</feature>
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</si>
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]]>
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</example>
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<example caption='Offer to Start a MP3 Stream (Alternate Stream Negotiation)'>
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<![CDATA[
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<si
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xmlns='http://jabber.org/protocol/si'
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id='s0'
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mime-type='audio/x-mp3'
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profile='streaming-audio'>
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<stream>s5b</stream>
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<stream>ibb</stream>
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</si>
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]]>
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</example>
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-->
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</section1>
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<section1 topic='Detailed Usage'>
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<section2 topic='Profiles'>
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<p>
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While Stream Initiation itself is helpful, it makes much more sense when
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what is being transported over the stream is known. Knowing this
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allows the Receiver to make a more educated choice about whether or not to
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accept the stream. This information is transported in Stream Initiation
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through a <em>profile</em>. A profile is a series of required and
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optional headers that describe the stream data or how the stream is to be
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used. Each Stream Initiation MUST have only one profile, so the stream
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usage is kept clear.
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</p>
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<p>
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Creating a profile is fairly simple. First, a name is chosen, the
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complete name is formatted like:</p>
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<code>
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http://jabber.org/protocol/si/profile/profile-name
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</code>
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<p>
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The complete name is what is presented in information discovery requests
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in order to show that the profile is supported. It is also used for the
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<si> profile attribute. Next, the information for the headers is
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decided upon. Each piece of information will be transported in a
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<header> tag. The name attribute is a descriptive key that can be
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looked up at the XMPP Registrar or XEP describing the profile. The
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actual data in the <header> is the fact related to the name
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attribute. It must also be stated whether the header is required or
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optional.
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</p>
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<p>
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This document does not define any profiles, nor does it place any restrictions
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on what type of information a profile should detail. This document also does
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not place restrictions on what may be placed in a <header>. Other
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XEPs will define profiles to be used with Stream Initiation.
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</p>
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</section2>
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<section2 topic='Stream Interaction'>
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<p>
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While Stream Initiation is not directly required for stream usage, it does
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provide many benefits. In order to fully appreciate these benefits,
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streams must link the Stream Initiation to the stream. The id
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attribute of the <si> node is intended to provide this link. It is
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out of scope of this document to define how streams will make use of this
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facility, but it does suggest some methods:</p>
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<ul>
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<li>
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Transport the Stream Initiation id with the stream negotitation as a
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namespaced attribute, such as:
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<code>
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<![CDATA[
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<stream id='0' xmlns:si='http://jabber.org/protocol/si' si:id='si0'>
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<start/>
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</stream>
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]]>
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</code>
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</li>
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<li>
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Transport the Stream Initiation id in a namespaced tag, such as:
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<code>
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<![CDATA[
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<stream id='0'>
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<start/>
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<si xmlns='http://jabber.org/protocol/si' id='si0'/>
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</stream>
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]]>
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</code>
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</li>
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</ul>
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</section2>
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<section2 topic='<si> Explanation'>
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<p>
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The attributes and data of <si> are fairly simple:</p>
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<ul>
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<li>
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<em>id</em> - An opaque identifier generated by the Sender.
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</li>
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<li>
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<em>mime-type</em> - The mime-type of the data being negotiated,
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selected by Sender.
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</li>
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<li>
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<em>profile</em> - The profile's fulle name, selected by Sender.
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</li>
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</ul>
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<p>The data of the node is a mixture of a feature negotiation for the stream
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and the profiles headers.
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</p>
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<p>
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When the Sender is offering a Stream Initiation all of the attributes must
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be present. The data MUST contain the required profile headers and the
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feature negotiation for the stream MUST be present with at least one
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option. The optional profile headers MAY also be in the node data.
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</p>
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<p>
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When the Receiver accepts a Stream Initiation the id attribute MUST be
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present, all other attributes MUST NOT be present. The selected stream
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MUST be in the feature negotiation for the stream. There MUST only be one
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selected stream.
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</p>
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</section2>
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<section2 topic='Error Codes'>
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<p>
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There are two error codes that are used. Following are the conditions,
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meanings and data:</p>
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<ul>
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<li>
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<em>Declining Transfer (403)</em>: During the Stream Initiation
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the Receiver may decline the transfer by sending the 403 error. The
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<error/> CDATA MAY contain a descriptive reason why, but is not
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necessary.
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</li>
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<li>
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<em>No Available Methods (406)</em>: When the Sender presents the
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available stream methods, and the Receiver can not use any of them,
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they send a 406 error. The <error/> CDATA is not important.
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</li>
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</ul>
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</section2>
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</section1>
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<section1 topic='Security Considerations'>
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<p>
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Data security concerns are left to the profiles to define. Wire security
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concerns are left to the stream definitions.
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</p>
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</section1>
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<section1 topic='IANA Considerations'>
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<p>
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This document uses the MIME types as recorded by IANA, but no other direct
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interaction is necessary.
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</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations'>
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<p>
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The "http://jabber.org/protocol/si" namespace will be registered.
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The registrar will track header profiles for different stream initiation
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uses.
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</p>
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</section1>
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<section1 topic='Formal Definition'>
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<section2 topic='Schema'>
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<p>To follow.</p>
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</section2>
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<section2 topic='DTD'>
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<p>To follow.</p>
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</section2>
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</section1>
|
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</xep>
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