xeps/xep-0177.xml

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<!DOCTYPE xep SYSTEM 'xep.dtd' [
  <!ENTITY % ents SYSTEM 'xep.ent'>
%ents;
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<xep>
<header>
  <title>Jingle Raw UDP Transport</title>
  <abstract>This document defines a Jingle transport method that results in sending data over a raw User Datagram Protocol (UDP) connection.</abstract>
  &LEGALNOTICE;
  <number>0177</number>
  <status>Experimental</status>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <approver>Council</approver>
  <dependencies>
    <spec>XMPP Core</spec>
    <spec>XEP-0166</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>TO BE ASSIGNED</shortname>
  &joebeda;
  &stpeter;
  &scottlu;
  &hildjj;
  &seanegan;
  <revision>
    <version>0.6</version>
    <date>2007-04-17</date>
    <initials>psa</initials>
    <remark><p>Specified Jingle conformance, including definition of transport type as lossy; added section on service discovery.</p></remark>
  </revision>
  <revision>
    <version>0.5</version>
    <date>2007-03-23</date>
    <initials>psa</initials>
    <remark><p>Updated to reflect changes to XEP-0166; clarified media data checking.</p></remark>
  </revision>
  <revision>
    <version>0.4</version>
    <date>2006-12-21</date>
    <initials>psa</initials>
    <remark><p>Recommended sending of candidate in initiation request to save a round trip and expedite the negotiation; removed name attribute; clarified flow of negotiation; modified spec to use provisional namespace before advancement to Draft (per XEP-0053).</p></remark>
  </revision>
  <revision>
    <version>0.3</version>
    <date>2006-10-31</date>
    <initials>psa</initials>
    <remark><p>Added informational messages; clarified connectivity checks and acceptance process; mentioned that the Raw UDP candidate is conceptually equivalent to the concept of an in-use candidate from the ICE specification; added reference to RFC 4347.</p></remark>
  </revision>
  <revision>
    <version>0.2</version>
    <date>2006-07-12</date>
    <initials>se/psa</initials>
    <remark><p>Removed candidate element and specified exchange of address information via transport-info messages; clarified usage of name attribute.</p></remark>
  </revision>
  <revision>
    <version>0.1</version>
    <date>2006-03-01</date>
    <initials>psa/jb</initials>
    <remark><p>Initial version (split from XEP-0166).</p></remark>
  </revision>
</header>
<section1 topic='Introduction' anchor='intro'>
  <p>&xep0166; defines a framework for negotiating and managing out-of-band data sessions over XMPP. In order to provide a flexible framework, the base Jingle specification defines neither data transport methods nor content formats, leaving that up to separate specifications. The current document defines a transport method for establishing and managing data between XMPP entities using a raw User Datagram Protocol (UDP) connection (see &rfc0768;). This "raw-udp" method results in a lossy transport method suitable for use in media applications where some packet loss is tolerable (e.g., audio and video).</p>
</section1>
<section1 topic='Requirements' anchor='reqs'>
  <p>The Jingle transport method defined herein is designed to meet the following requirements:</p>
  <ol>
    <li>Make it possible to establish and manage out-of-band connections between two XMPP entities over the IP address and port that the parties consider most likely to succeed.</li>
    <li>Make it relatively easy to implement support in standard Jabber/XMPP clients.</li>
    <li>Where communication with non-XMPP entities is needed, push as much complexity as possible onto server-side gateways between the XMPP network and the non-XMPP network.</li>
  </ol>
  <p>Note: The Raw UDP transport does not provide traversal of Network Address Translators (NATs) and is provided only for the purpose of specifying the IP address and port that an entity considers most likely to succeed without the need for NAT traversal. <note>This is also helpful for bootstrapping of Jingle implementation by developers working on a local network.</note> If NAT traversal is needed, &xep0176; SHOULD be used.</p>
</section1>
<section1 topic='Jingle Conformance' anchor='conformance'>
   <p>In accordance with Section 8 of <cite>XEP-0166</cite>, this document specifies the following information related to the Jingle Raw UDP transport type:</p>
   <ol>
     <li><p>The transport negotiation process is defined in the <link url='#protocol'>Protocol Description</link> section of this document.</p></li>
     <li><p>The semantics of the &DESCRIPTION; element are defined in the <link url='#initiate'>Transport Initiation</link> section of this document.</p></li>
     <li><p>Successful negotiation of the Raw UDP method results in use of a lossy transport that is suitable for applications where some packet loss is tolerable, such as audio and video.</p></li>
     <li><p>If multiple components are to be communicated over the transport, the first component shall be associated with the port in the transport initiation stanza and the second component (e.g., for RTCP) shall be associated with a UDP port that is one number higher than the specified port (e.g., if the specified port is 13540 then the port for the second component shall be 13541).</p></li>
   </ol>
</section1>
<section1 topic='Protocol Description' anchor='protocol'>
  <section2 topic='Transport Initiation' anchor='initiate'>
    <p>In order for the initiator in a Jingle exchange to start the negotiation, it MUST send a Jingle "session-initiate" stanza as described in <cite>XEP-0166</cite>. This stanza MUST include at least one content type. If the initiator wishes to negotiate the Raw UDP transport for a given content type, it MUST include a &TRANSPORT; child element qualified by the 'http://www.xmpp.org/extensions/xep-0177.html#ns' namespace (see <link url='#ns'>Protocol Namespaces</link>), which MUST <note>This is required to avoid a round trip and help expedite the negotiation.</note> include the initiator's Raw UDP candidate via the 'ip', 'port', 'generation', and 'name' attributes of the &CANDIDATE; element.</p>
    <example caption="Initiation Example"><![CDATA[
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' id='jingle1' type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-initiate'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content'>
      <description ...>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'>
        <candidate ip='10.1.1.104' port='13540' generation='0'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>The 'generation', 'ip', and 'port' attributes are REQUIRED. The 'ip' and 'port' attributes are self-explanatory. The 'generation' attribute provides a tracking mechanism for determining which version of this candidate is in force (this is useful if the candidate is redefined mid-stream, for example if the port is changed).</p>
    <p>Note: The "Raw UDP candidate" is the candidate that the entity has reason to believe will be most likely to succeed for that content type, and thus is equivalent to the "in-use" candidate as described in &ice;. <note>In older versions of XEP-0166, this was referrred to as the "default candidate".</note> This is not necessarily the entity's preferred address for communication, but instead is the "address most likely to succeed", i.e., the address that is assumed to be reachable by the vast majority of target entities. To determine reachability, the client needs classify ahead of time the permissiveness of the NAT or firewall it is behind, if any. It then SHOULD assign the Raw UDP candidate as follows, where the candidate types are as described in <cite>ICE</cite>:</p>
    <table caption='Raw UDP Candidate Assignment'>
      <tr>
        <th>NAT Type</th>
        <th>Recommended Raw UDP Candidate Type</th>
      </tr>
      <tr>
        <td>None</td>
        <td>Host candidate</td>
      </tr>
      <tr>
        <td>Symmetric (not permissive)</td>
        <td>Relay candidate</td>
      </tr>
      <tr>
        <td>Permissive</td>
        <td>Server reflexive or peer reflexive candidate discovered via &rfc3489;</td>
      </tr>
    </table>
  </section2>
  <section2 topic='Responder Response' anchor='response'>
    <p>As described in <cite>XEP-0166</cite>, to provisionally accept the session initiation request, the receiver returns an IQ-result:</p>
    <example caption="Responder Provisionally Accepts the Session Request"><![CDATA[
<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' type='result' id='jingle1'/>
    ]]></example>
    <p>Once the responder provisionally accepts the session, it:</p>
    <ul>
      <li>MUST check the initiator's Raw UDP candidate by attempting to send data via UDP to the specified IP and port (see next section).</li>
      <li>SHOULD send its own Raw UDP candidate to the initiator via a Jingle "transport-info" message.</li>
      <li>MAY send an informational message.</li>
    </ul>
    <p>These are done simultaneously in order to ensure that a connection can be made, since the initiator's Raw UDP candidate may not result in success.</p>
    <section3 topic='Checking the Initiator&apos;s Candidate' anchor='response-check'>
      <p>The responder MUST immediately attempt to send data to the IP and port specified in the initiation request. Because delivery of UDP data is not acknowledged, the data SHOULD be sent using the echo protocol (&rfc0862;) over the IP address and port specified in the Raw UDP candidate; if the data is echoed back, the recipient would then send a Jingle "content-accept" (or "session-accept") action to the initiator.</p>
      <example caption="Responder Returns Transport-Accept"><![CDATA[
<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' type='set' id='accept1'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-accept'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content'>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'>
        <candidate name='myvoicedata' ip='10.1.1.104' port='13540' generation='0'/>
      </transport>
    </content>
  </jingle>
</iq>
      ]]></example>
      <p>The initiator MUST then acknowledge acceptance by returning an IQ result (or a standard XMPP error).</p>
      <example caption="Initiator Acknowledges Transport Accept"><![CDATA[
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' type='result' id='accept1'/>
      ]]></example>
    </section3>
    <section3 topic='Sending A Candidate' anchor='response-candidate'>
      <p>While checking the initiator's Raw UDP candidate, the responder SHOULD send its own Raw UDP candidate to the initiator by sending a transport-info message to the initiator, as shown in the following example.</p>
      <example caption="Responder Sends Its Raw UDP Candidate"><![CDATA[
<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle2' type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='transport-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content'>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'>
        <candidate ip='208.245.212.67' port='9876' generation='0'/>
      </transport>
    </content>
  </jingle>
</iq>
      ]]></example>
      <p>The initiator MUST then acknowledge receipt by returning an IQ result (or a standard XMPP error).</p>
      <example caption="Initiator Acknowledges Receipt of Candidate"><![CDATA[
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' type='result' id='jingle2'/>
      ]]></example>
      <p>Naturally, the initiator then MUST also check the responder's Raw UDP candidate by following the checking procedure outlined above.</p>
    </section3>
    <section3 topic='Sending An Informational Message' anchor='response-info'>
      <p>While checking the initiator's Raw UDP candidate, the responder MAY send an informational message to communicate the status of transport checking. The informational message MUST be an IQ-set containing a &JINGLE; element of type "session-info", where the informational message is a payload  element specified in the <link url='#info'>Informational Messages</link> section of this document.</p>
    </section3>
  </section2>

  <section2 topic='Informational Messages' anchor='protocol-info'>
    <p>Informational messages MAY be sent by the receiver within the context of the Raw UDP transport to communicate the status of transport checking. The informational message MUST be an IQ-set containing a &JINGLE; element of type "session-info", where the informational message is a payload  element qualified by the 'http://www.xmpp.org/extensions/xep-0177.html#ns-info' namespace (see <link url='#ns'>Protocol Namespaces</link>). The following payload elements are defined:</p>
    <table caption='Information Payload Elements'>
      <tr>
        <th>Element</th>
        <th>Meaning</th>
      </tr>
      <tr>
        <td>&lt;failed/&gt;</td>
        <td>Connectivity checks failed.</td>
      </tr>
      <tr>
        <td>&lt;succeeded/&gt;</td>
        <td>Connectivity checks succeeded.</td>
      </tr>
      <tr>
        <td>&lt;trying/&gt;</td>
        <td>Connectivity checks are underway.</td>
      </tr>
    </table>
    <p>Note: Because the informational message is sent in an IQ-set, the receiving party MUST return either an IQ-result or an IQ-error (normally only an IQ-result to acknowledge receipt; no error flows are defined or envisioned at this time).</p>
  </section2>
</section1>

<section1 topic='Determining Support' anchor='support'>
  <p>If an entity supports the Jingle Raw UDP transport, it MUST return a feature of "http://www.xmpp.org/extensions/xep-0177.html#ns" &NSNOTE; in response to &xep0030; information requests.</p>
  <example caption="Service Discovery information request"><![CDATA[
<iq type='get'
    from='romeo@montague.net/orchard'
    to='juliet@capulet.com/balcony'
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  ]]></example>
  <example caption="Service Discovery information response"><![CDATA[
<iq type='result'
    from='juliet@capulet.com/balcony'
    to='romeo@montague.net/orchard'
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    ...
    <feature var='http://www.xmpp.org/extensions/xep-0177.html#ns'/>
    ...
  </query>
</iq>
  ]]></example>
</section1>

<section1 topic='Security Considerations' anchor='security'>
  <p>In order to secure the data stream that is negotiated via the Jingle ICE transport, implementations SHOULD use encryption methods appropriate to the transport method and media being exchanged (for details regarding audio and video exchanges via RTP, refer to <cite>XEP-0167</cite> and <cite>XEP-0180</cite>).</p>
</section1>

<section1 topic='IANA Considerations' anchor='iana'>
  <p>This document requires no interaction with &IANA;.</p>
</section1>

<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
  <section2 topic='Protocol Namespaces' anchor='ns'>
    <p>Until this specification advances to a status of Draft, its associated namespaces shall be "http://www.xmpp.org/extensions/xep-0177.html#ns" and "http://www.xmpp.org/extensions/xep-0177.html#ns-info"; upon advancement of this specification, the &REGISTRAR; shall issue permanent namespaces in accordance with the process defined in Section 4 of &xep0053;.</p>
  </section2>
  <section2 topic='Jingle Transport Methods' anchor='registrar-transports'>
    <p>The XMPP Registrar shall include "raw-udp" in its registry of Jingle transport methods. The registry submission is as follows:</p>
    <code><![CDATA[
<transport>
  <name>raw-udp</name>
  <desc>A method for exchanging data over a raw UDP connection.</desc>
  <type>lossy</type>
  <doc>XEP-0176</doc>
</transport>
    ]]></code>
  </section2>
</section1>
<section1 topic='XML Schema' anchor='schema'>
  <code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://www.xmpp.org/extensions/xep-0177.html#ns'
    xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'
    elementFormDefault='qualified'>

  <xs:element name='transport'>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref='candidate' minOccurs='0' maxOccurs='1'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name='candidate'>
    <xs:complexType>
      <xs:simpleContent>
        <xs:extension base='empty'>
          <xs:attribute name='generation' type='xs:unsignedByte' use='required'/>
          <xs:attribute name='ip' type='xs:string' use='required'/>
          <xs:attribute name='port' type='xs:unsignedShort' use='required'/>
        </xs:extension>
      </xs:simpleContent>
    </xs:complexType>
  </xs:element>

  <xs:simpleType name='empty'>
    <xs:restriction base='xs:string'>
      <xs:enumeration value=''/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>
  ]]></code>
</section1>
</xep>