xeps/xep-0167.xml

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  <!ENTITY % ents SYSTEM 'xep.ent'>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
<header>
  <title>Jingle Audio via RTP</title>
  <abstract>This specification defines a Jingle application type for negotiating a voice chat or other audio session. The application type uses the Real-time Transport Protocol (RTP) for the underlying media exchange and provides a straightforward mapping to Session Description Protocol (SDP) for interworking with SIP media endpoints.</abstract>
  &LEGALNOTICE;
  <number>0167</number>
  <status>Proposed</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>
  &scottlu;
  &stpeter;
  &seanegan;
  &robmcqueen;
  <revision>
    <version>0.15</version>
    <date>2008-01-11</date>
    <initials>psa</initials>
    <remark><p>Removed content-accept after content-remove per XEP-0166.</p></remark>
  </revision>
  <revision>
    <version>0.14</version>
    <date>2008-01-03</date>
    <initials>psa</initials>
    <remark><p>Modified examples to track changes to XEP-0176.</p></remark>
  </revision>
  <revision>
    <version>0.13</version>
    <date>2007-12-06</date>
    <initials>psa</initials>
    <remark><p>To track changes to XEP-0166, modified busy scenario and removed unsupported-codecs error.</p></remark>
  </revision>
  <revision>
    <version>0.12</version>
    <date>2007-11-27</date>
    <initials>psa</initials>
    <remark><p>Further editorial review.</p></remark>
  </revision>
  <revision>
    <version>0.11</version>
    <date>2007-11-15</date>
    <initials>psa</initials>
    <remark><p>Editorial review and consistency check; moved voice chat scenarios from XEP-0166 to this specification.</p></remark>
  </revision>
  <revision>
    <version>0.10</version>
    <date>2007-11-13</date>
    <initials>psa</initials>
    <remark><p>Removed info message for busy since it is now a Jingle-specific error condition defined in XEP-0166; defined info message for active.</p></remark>
  </revision>
  <revision>
    <version>0.9</version>
    <date>2007-04-17</date>
    <initials>psa</initials>
    <remark><p>Specified Jingle conformance, including the preference for lossy transports over reliable transports and the process of sending and receiving audio content over each transport type.</p></remark>
  </revision>
  <revision>
    <version>0.8</version>
    <date>2007-03-23</date>
    <initials>psa/ram</initials>
    <remark><p>Renamed to mention RTP as the associated transport; corrected negotiation flow to be consistent with SIP/SDP (each party specifies a list of the payload types it can receive); added profile attribute to content element in order to specify RTP profile in use.</p></remark>
  </revision>
  <revision>
    <version>0.7</version>
    <date>2006-12-21</date>
    <initials>psa</initials>
    <remark><p>Modified spec to use provisional namespace before advancement to Draft (per XEP-0053).</p></remark>
  </revision>
  <revision>
    <version>0.6</version>
    <date>2006-10-31</date>
    <initials>psa/se</initials>
    <remark><p>Specified how to include SDP parameters and codec-specific parameters; clarified negotiation process; added Speex examples; removed queued info message.</p></remark>
  </revision>
  <revision>
    <version>0.5</version>
    <date>2006-08-23</date>
    <initials>psa</initials>
    <remark><p>Modified namespace to track XEP-0166.</p></remark>
  </revision>
  <revision>
    <version>0.4</version>
    <date>2006-07-12</date>
    <initials>se/psa</initials>
    <remark><p>Specified when to play received audio (early media); specified that DTMF must use in-band signalling (XEP-0181).</p></remark>
  </revision>
  <revision>
    <version>0.3</version>
    <date>2006-03-20</date>
    <initials>psa</initials>
    <remark><p>Defined info messages for hold and mute.</p></remark>
  </revision>
  <revision>
    <version>0.2</version>
    <date>2006-02-13</date>
    <initials>psa</initials>
    <remark><p>Defined info message for busy; added info message examples; recommended use of Speex; updated schema and XMPP Registrar considerations.</p></remark>
  </revision>
  <revision>
    <version>0.1</version>
    <date>2005-12-15</date>
    <initials>psa</initials>
    <remark><p>Initial version.</p></remark>
  </revision>
  <revision>
    <version>0.0.3</version>
    <date>2005-12-05</date>
    <initials>psa</initials>
    <remark><p>Described service discovery usage; defined initial informational messages.</p></remark>
  </revision>
  <revision>
    <version>0.0.2</version>
    <date>2005-10-27</date>
    <initials>psa</initials>
    <remark><p>Added SDP mapping, security considerations, IANA considerations, XMPP Registrar considerations, and XML schema.</p></remark>
  </revision>
  <revision>
    <version>0.0.1</version>
    <date>2005-10-21</date>
    <initials>psa/sl</initials>
    <remark><p>First draft.</p></remark>
  </revision>
</header>

<section1 topic='Introduction' anchor='intro'>
  <p>&xep0166; can be used to initiate and negotiate a wide range of peer-to-peer sessions. One session type of interest is audio chat. This document specifies an application format for negotiating Jingle audio sessions, where the media is exchanged over the Realtime Transport Protocol (RTP; see &rfc3550;).</p>
</section1>

<section1 topic='Requirements' anchor='reqs'>
  <p>The Jingle application format defined herein is designed to meet the following requirements:</p>
  <ol>
    <li>Enable negotiation of parameters necessary for audio chat over Realtime Transport Protocol (RTP).</li>
    <li>Map these parameters to Session Description Protocol (SDP; see &rfc4566;) to enable interoperability.</li>
    <li>Define informational messages related to audio chat (e.g., ringing, on hold, on mute).</li>
  </ol>
</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 Audio via RTP application type:</p>
   <ol>
     <li><p>The application format negotiation process is defined in the <link url='#negotiation'>Negotiating a Jingle Audio Session</link> section of this document.</p></li>
     <li><p>The semantics of the &DESCRIPTION; element are defined in the <link url='#format'>Application Format</link> section of this document.</p></li>
     <li><p>A mapping of Jingle semantics to the Session Description Protocol is provided in the <link url='#sdp'>Mapping to Session Description Protocol</link> section of this document.</p></li>
     <li><p>A Jingle audio session SHOULD use a lossy transport method such as &xep0177; or the "ice-udp" method specified in &xep0176;, but MAY use a reliable transport such as "ice-tcp" if a low-bandwidth codec is employed.</p></li>
     <li>
       <p>Content is to be sent and received as follows:</p>
       <ul>
         <li><p>For lossy transports, outbound audio content shall be encoded into RTP packets and each packet shall be sent individually over the transport. Each inbound packet received over the transport is an RTP packet.</p></li>
         <li><p>For reliable transports, outbound audio content shall be encoded into RTP packets and each packet data shall be sent in succession over the transport. Incoming data received over the transport shall be processed as a stream of RTP packets, where each RTP packet boundary marks the location of the next packet.</p></li>
       </ul>
     </li>
   </ol>
</section1>

<section1 topic='Application Format' anchor='format'>
  <p>A Jingle audio session is described by a content type that contains one application format and one transport method. The application format consists of one or more encodings contained within a wrapper &lt;description/&gt; element qualified by the 'http://www.xmpp.org/extensions/xep-0167.html#ns' namespace &NSNOTE;. In the language of <cite>RFC 4566</cite> each encoding is a payload-type; therefore, each &lt;payload-type/&gt; element specifies an encoding that can be used for the audio stream, as illustrated in the following example.</p>
  <example caption="Audio description format"><![CDATA[
    <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
      <payload-type id='96' name='speex' clockrate='16000'/>
      <payload-type id='97' name='speex' clockrate='8000'/>
      <payload-type id='18' name='G729'/>
      <payload-type id='103' name='L16' clockrate='16000' channels='2'/>
      <payload-type id='98' name='x-ISAC' clockrate='8000'/>
      <payload-type id='102' name='iLBC'/>
      <payload-type id='4' name='G723'/>
      <payload-type id='0' name='PCMU' clockrate='16000'/>
      <payload-type id='8' name='PCMA'/>
      <payload-type id='13' name='CN'/>
    </description>
  ]]></example>
  <p>The &DESCRIPTION; element is intended to be a child of a &CONTENT; element as specified in <cite>XEP-0166</cite>.</p>
  <p>The &CONTENT; element SHOULD possess a 'profile' attribute that specifies the exact protocol in use as would be encapsulated in SDP (e.g., "RTP/AVP" or "UDP/TLS/RTP/SAVP").</p>
  <p>The encodings SHOULD be provided in order of preference by placing the most-preferred &PAYLOADTYPE; element as the first child of the &DESCRIPTION; element (etc.).</p>
  <p>The allowable attributes of the &PAYLOADTYPE; element are as follows:</p>
  <table caption='Payload-Type Attributes'>
    <tr>
      <th>Attribute</th>
      <th>Description</th>
      <th>Datatype</th>
      <th>Inclusion</th>
    </tr>
    <tr>
      <td>channels</td>
      <td>The number of channels; if omitted, it MUST be assumed to contain one channel</td>
      <td>positiveInteger (defaults to 1)</td>
      <td>RECOMMENDED</td>
    </tr>
    <tr>
      <td>clockrate</td>
      <td>The sampling frequency in Hertz</td>
      <td>positiveInteger</td>
      <td>RECOMMENDED</td>
    </tr>
    <tr>
      <td>id</td>
      <td>The payload identifier</td>
      <td>positiveInteger</td>
      <td>REQUIRED</td>
    </tr>
    <tr>
      <td>maxptime</td>
      <td>Maximum packet time as specified in RFC 4566</td>
      <td>positiveInteger</td>
      <td>OPTIONAL</td>
    </tr>
    <tr>
      <td>name</td>
      <td>The appropriate subtype of the audio MIME type</td>
      <td>string</td>
      <td>RECOMMENDED for static payload types, REQUIRED for dynamic payload types</td>
    </tr>
    <tr>
      <td>ptime</td>
      <td>Packet time as specified in RFC 4566</td>
      <td>positiveInteger</td>
      <td>OPTIONAL</td>
    </tr>
  </table>
  <p>In Jingle Audio, the encodings are used in the context of RTP. The most common encodings for the Audio/Video Profile (AVP) of RTP are listed in &rfc3551; (these "static" types are reserved from payload ID 0 through payload ID 95), although other encodings are allowed (these "dynamic" types use payload IDs 96 to 127) in accordance with the dynamic assignment rules described in Section 3 of <cite>RFC 3551</cite>. The payload IDs are represented in the 'id' attribute.</p>
  <p>Each &lt;payload-type/&gt; element MAY contain one or more child elements that specify particular parameters related to the payload. For example, as described in &rtpspeex;, the "cng", "mode", and "vbr" parameters may be specified in relation to usage of the Speex <note>See &lt;<link url='http://www.speex.org/'>http://www.speex.org/</link>&gt;.</note> codec. Where such parameters are encoded via the "fmtp" SDP attribute, they shall be represented in Jingle via the following format:</p>
  <code><![CDATA[
<parameter name='foo' value='bar'/>
  ]]></code>
  <p>Note: The parameter names are effectively guaranteed to be unique, since &IANA; maintains a registry of SDP parameters (see &lt;<link url='http://www.iana.org/assignments/sdp-parameters'>http://www.iana.org/assignments/sdp-parameters</link>&gt;).</p>
</section1>

<section1 topic='Negotiating a Jingle Audio Session' anchor='negotiation'>
  <p>When the initiator sends a session-initiate stanza to the responder, the &DESCRIPTION; element includes all of the payload types that the initiator can receive for Jingle audio (each one encapsulated in a separate &PAYLOADTYPE; element):</p>
  <example caption="Initiation"><![CDATA[
<iq from='romeo@montague.net/orchard'
    id='jingleaudio1'
    to='juliet@capulet.com/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'>
          action='session-initiate'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <content name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='96' name='speex' clockrate='16000'/>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='103' name='L16' clockrate='16000' channels='2'/>
        <payload-type id='98' name='x-ISAC' clockrate='8000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
  ]]></example>
  <p>Upon receiving the session-initiate stanza, the responder determines whether it can proceed with the negotiation. The general Jingle error cases are specified in <cite>XEP-0166</cite> and illustrated in the <link url='#scenarios'>Scenarios</link> section of this document.</p>
  <p>If there is no error, the responder acknowledges the session initiation request.</p>
  <example caption="Responder acknowledges session-initiate"><![CDATA[
  <iq from='juliet@capulet.com/balcony'
      id='jingleaudio1'
      to='romeo@montague.net/orchard'
      type='result'/>
  ]]></example>
  <p>The responder then should send a list of the payload types that it can receive via a Jingle "content-accept" (or "session-accept") action. The list that the responder sends MAY include any payload types (not a subset of the payload types sent by the initiator) but SHOULD retain the ID numbers specified by the initiator. The order of the &PAYLOADTYPE; elements indicates the responder's preferences, with the most-preferred types first.</p>
  <example caption="Responder accepts content type"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='jingleaudio2'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'>
          action='content-accept'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <content name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='0' name='PCMU' />
        <payload-type id='102' name='iLBC'/>
        <payload-type id='4' name='G723'/>
        <payload-type id='8' name='PCMA'/>
        <payload-type id='13' name='CN'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
  ]]></example>
  <p>The initiator acknowledges the 'content-accept' with an empty IQ result:</p>
  <example caption="Initiator acknowledges modified application format"><![CDATA[
  <iq from='romeo@montegue.net/orchard'
      id='jingleaudio2'
      to='juliet@capulet.com/balcony'
      type='result'/>
  ]]></example>
  <p>After successful transport negotiation (not shown here), the responder then accepts the session:</p>
  <example caption="Responder definitively accepts the session"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='accept1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-accept'
          initiator='romeo@montague.net/orchard'
          responder='juliet@capulet.com/balcony'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='0' name='PCMU' />
        <payload-type id='102' name='iLBC'/>
        <payload-type id='4' name='G723'/>
        <payload-type id='8' name='PCMA'/>
        <payload-type id='13' name='CN'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1678246398'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
  ]]></example>
  <p>And the initiator acknowledges session acceptance:</p>
  <example caption="Initiator acknowledges session acceptance"><![CDATA[
  <iq from='romeo@montague.net/orchard'
      id='accept1'
      to='juliet@capulet.com/balcony'
      type='result'/>
  ]]></example>
  <p>Note: Because a "session-accept" action implicitly indicates acceptance of the application format (i.e., "content-accept"), it is not necessary to send a separate "content-accept" action. This flow is shown for completeness only.</p>
</section1>

<section1 topic='Mapping to Session Description Protocol' anchor='sdp'>
  <p>The SDP media type for Jingle Audio via RTP is "audio" (see Section 8.2.1 of <cite>RFC 4566</cite>).</p>
  <p>If the payload type is static (payload-type IDs 0 through 95 inclusive), it MUST be mapped to a media field defined in <cite>RFC 4566</cite>. The generic format for the media field is as follows:</p>
  <code><![CDATA[
m=<media> <port> <transport> <fmt list>
  ]]></code>
  <p>In the context of Jingle audio sessions, the &lt;media&gt; is "audio", the &lt;port&gt; is the preferred port for such communications (which may be determined dynamically), the &lt;transport&gt; is whatever profile is negotiated via the 'profile' attribute of the &CONTENT; element in the Jingle negotiation (e.g., "RTP/AVP"), and the &lt;fmt list&gt; is the payload-type ID.</p>
  <p>For example, consider the following static payload-type:</p>
  <example caption="Jingle format for static payload-type"><![CDATA[
<payload-type id="13" name="CN"/>
  ]]></example>
  <p>That Jingle-formatted information would be mapped to SDP as follows:</p>
  <example caption="SDP mapping of static payload-type"><![CDATA[
m=audio 9999 RTP/AVP 13
  ]]></example>
  <p>If the payload type is dynamic (payload-type IDs 96 through 127 inclusive), it SHOULD be mapped to an SDP media field plus an SDP attribute field named "rtpmap".</p>
  <p>For example, consider a payload of 16-bit linear-encoded stereo audio sampled at 16KHz associated with dynamic payload-type 96:</p>
  <example caption="Jingle format for dynamic payload-type"><![CDATA[
<payload-type id='96' name='speex' clockrate='16000'/>
  ]]></example>
  <p>That Jingle-formatted information would be mapped to SDP as follows:</p>
  <example caption="SDP mapping of dynamic payload-type"><![CDATA[
m=audio 9999 RTP/AVP 96
a=rtpmap:96 speex/16000
  ]]></example>
  <p>As noted, if additional parameters are to be specified, they shall be represented as attributes of the &lt;parameter/&gt; child of the &PAYLOADTYPE; element, as in the following example.</p>
  <example caption="Jingle format for dynamic payload-type with parameters"><![CDATA[
<payload-type id='96' name='speex' clockrate='16000' ptime='40'>
  <parameter name='vbr' value='on'/>
  <parameter name='cng' value='on'/>
</payload-type>
  ]]></example>
  <p>That Jingle-formatted information would be mapped to SDP as follows:</p>
  <example caption="SDP mapping of dynamic payload-type with parameters"><![CDATA[
m=audio 9999 RTP/AVP 96
a=rtpmap:96 speex/16000
a=ptime:40
a=fmtp:96 vbr=on;cng=on
  ]]></example>
</section1>

<section1 topic='Informational Messages' anchor='info'>
  <section2 topic='Format' anchor='info-format'>
    <p>Informational messages may be sent by either party within the context of Jingle to communicate the status of a Jingle audio session, device, or principal. 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-0167.html#ns-info' namespace; the following payload elements are defined: <note>A &lt;trying/&gt; element (equivalent to the SIP 100 Trying response code) is not necessary, since each session-level action is acknowledged via XMPP IQ semantics.</note></p>
    <table caption='Information Payload Elements'>
      <tr>
        <th>Element</th>
        <th>Meaning</th>
      </tr>
      <tr>
        <td>&lt;active/&gt;</td>
        <td>The principal or device is again actively participating in the session after having been on hold or on mute.</td>
      </tr>
      <tr>
        <td>&lt;hold/&gt;</td>
        <td>The principal is temporarily pausing the chat (i.e., putting the other party on hold).</td>
      </tr>
      <tr>
        <td>&lt;mute/&gt;</td>
        <td>The principal is temporarily stopping audio output but continues to accept audio input.</td>
      </tr>
      <tr>
        <td>&lt;ringing/&gt;</td>
        <td>The device is ringing but the principal has not yet interacted with it to answer (this maps to the SIP 180 response code).</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>
  <section2 topic='Examples' anchor='info-examples'>
    <example caption="Responder sends active message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='active1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'>
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <active xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder sends hold message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='hold1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <hold xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder sends mute message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='mute1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <mute xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder sends ringing message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='ringing1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <ringing xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
  </section2>
</section1>

<section1 topic='Determining Support' anchor='support'>
  <p>If an entity supports Jingle audio exchanges via RTP, it MUST advertise that fact by returning a feature of "http://www.xmpp.org/extensions/xep-0167.html#ns" &NSNOTE; in response to &xep0030; information requests.</p>
  <example caption="Service discovery information request"><![CDATA[
<iq from='romeo@montague.net/orchard'
    id='disco1'
    to='juliet@capulet.com/balcony'
    type='get'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  ]]></example>
  <example caption="Service discovery information response"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='disco1'
    to='romeo@montague.net/orchard'
    type='result'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    ...
    <feature var='http://www.xmpp.org/extensions/xep-0166.html#ns'/>
    <feature var='http://www.xmpp.org/extensions/xep-0167.html#ns'/>
    ...
  </query>
</iq>
  ]]></example>
  <p>Naturally, support MAY also be determined via the dynamic, presence-based profile of Service Discovery defined in &xep0115;.</p>
</section1>

<section1 topic='Scenarios' anchor='scenarios'>
  <p>The following sections show a number of Jingle audio scenarios, in relative order of complexity.</p>
  <section2 topic='Responder is Busy' anchor='scenarios-busy'>
    <p>In this scenario, Romeo initiates a voice chat with Juliet but she is otherwise engaged.</p>
    <p>The session flow is as follows:</p>
    <code><![CDATA[
Romeo                         Juliet
  |                             |
  |   session-initiate          |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-info (ringing)    |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   terminate                 |
  |   (reasoncode = busy)       |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |                             |
    ]]></code>
    <p>The protocol flow is as follows.</p>
    <example caption="Initiator sends session-initiate"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='jingle1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-initiate'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='96' name='speex' clockrate='16000'/>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='103' name='L16' clockrate='16000' channels='2'/>
        <payload-type id='98' name='x-ISAC' clockrate='8000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder sends provisional acceptance"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='accept1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends ringing message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='ringing1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <ringing xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Initiator acknowledges ringing message"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='ringing1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <example caption="Responder terminates the session"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='term1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-terminate'
          initiator='romeo@montague.lit/orchard'
          reasoncode='busy'
          reasontext='No time to chat right now!'
          sid='a73sjjvkla37jfea'/>
</iq>
    ]]></example>
    <p>The other party then acknowledges termination of the session:</p>
    <example caption="Initiator acknowledges termination"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='term1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
  </section2>
  <section2 topic='Jingle Audio via RTP/AVP, Negotiated with ICE-UDP' anchor='scenarios-voicechat'>
    <p>In this scenario, Romeo initiates a voice chat with Juliet using a transport method of ICE-UDP. The parties also exchange informational messages.</p>
    <p>The session flow is as follows:</p>
    <code><![CDATA[
Romeo                         Juliet
  |                             |
  |   session-initiate          |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-info (ringing)    |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   transport-info (X times)  |
  |   (with acks)               |
  |<--------------------------->|
  |   STUN connectivity checks  |
  |<--------------------------->|
  |   content-modify            |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-accept            |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   AUDIO (RTP)               |
  |<===========================>|
  |   session-terminate         |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |                             |
    ]]></code>
    <p>The protocol flow is as follows.</p>
    <example caption="Initiator sends session-initiate"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='jingle1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-initiate'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='96' name='speex' clockrate='16000'/>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='103' name='L16' clockrate='16000' channels='2'/>
        <payload-type id='98' name='x-ISAC' clockrate='8000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder sends provisional acceptance"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='accept1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends ringing message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='ringing1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <ringing xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Initiator acknowledges ringing message"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='ringing1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>Because the parties have chosen the Jingle ICE-UDP Transport Method, the initiator and responder exchange an open-ended number of possible candidate transports, perform connectivity checks, and agree upon a candidate transport as explained in <cite>XEP-0176</cite>. Once ICE negotiation is completed, the initiator sends a content-modify action to the responder.</p>
    <example caption="Initiator requests content-modify"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='mod1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-modify'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        [ ... ]
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1694498815'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   rel-addr='10.0.1.1'
                   rel-port='8998'
                   rem-addr='192.0.2.1'
                   rem-port='3478'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>The responder then acknowledges the content-modify action and sends a session-accept action.</p>
    <example caption="Responder acknowledges content-modify"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='mod1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends session-accept"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='accept1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-accept'
          initiator='romeo@montague.lit/orchard'
          responder='juliet@capulet.lit/balcony'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='0' name='PCMU' />
        <payload-type id='102' name='iLBC'/>
        <payload-type id='4' name='G723'/>
        <payload-type id='8' name='PCMA'/>
        <payload-type id='13' name='CN'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1694498815'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   rel-addr='10.0.1.1'
                   rel-port='8998'
                   rem-addr='192.0.2.1'
                   rem-port='3478'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>If the payload types and transport candidate can be successfully used by both parties, then the initiator acknowledges the session-accept action.</p>
    <example caption="Initiator acknowledges session-accept"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='accept1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>The parties now begin to exchange media. In this case they would exchange audio using the Speex codec at a clockrate of 8000 since that is the highest-priority codec for the responder (as determined by the XML order of the &PAYLOADTYPE; children).</p>
    <p>The parties may continue the session as long as desired.</p>
    <p>Eventually, one of the parties terminates the session.</p>
    <example caption="Responder terminates the session"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='term1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-terminate'
          initiator='romeo@montague.lit/orchard'
          reasoncode='no-error'
          reasontext='Sorry, gotta go!'
          sid='a73sjjvkla37jfea'/>
</iq>
    ]]></example>
    <p>The other party then acknowledges termination of the session:</p>
    <example caption="Initiator acknowledges termination"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='term1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
  </section2>
  <section2 topic='Jingle Audio and Video via RTP/AVP, Negotiated with ICE-UDP' anchor='scenarios-voicechat'>
    <p>In this scenario, Romeo initiates a combined audio and video chat with Juliet using a transport method of ICE-UDP. Juliet at first refuses the video portion, then later offers to add video, which Romeo accepts. The parties also exchange various informational messages</p>
    <p>The session flow is as follows:</p>
    <code><![CDATA[
Romeo                         Juliet
  |                             |
  |   session-initiate          |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-info (ringing)    |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   content-remove            |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   transport-info (X times)  |
  |   (with acks)               |
  |<--------------------------->|
  |   STUN connectivity checks  |
  |<--------------------------->|
  |   content-modify            |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-accept            |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   AUDIO (RTP)               |
  |<===========================>|
  |   session-info (hold)       |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   session-info (active)     |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   content-add               |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   content-accept            |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   AUDIO + VIDEO (RTP)       |
  |<===========================>|
  |   session-terminate         |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |                             |
    ]]></code>
    <p>The protocol flow is as follows.</p>
    <example caption="Initiation"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='jingle1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-initiate'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='96' name='speex' clockrate='16000'/>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='103' name='L16' clockrate='16000' channels='2'/>
        <payload-type id='98' name='x-ISAC' clockrate='8000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
    <content creator='initiator' name='this-is-the-video-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0180.html#ns'>
        <payload-type id='96' name='theora' clockrate='90000' height='720' width='1280'>
          <parameter name='delivery-method' value='inline'/>
          <parameter name='configuration' value='somebase16string'/>
          <parameter name='sampling' value='YCbCr-4:2:2'/>
        </payload-type>
        <payload-type id='28' name='nv' clockrate='90000'/>
        <payload-type id='25' name='CelB' clockrate='90000'/>
        <payload-type id='32' name='MPV' clockrate='90000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder acknowledges session-initiate request"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='jingle1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends ringing message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='ringing1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <ringing xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Initiator acknowledges ringing message"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='ringing1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>However, Juliet doesn't want to do video because she is having a bad hair day, so she sends a "content-remove" request to Romeo.</p>
    <example caption="Responder requests content-remove"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='remove1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-remove'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-video-content' profile='RTP/AVP'/>
  </jingle>
</iq>
    ]]></example>
    <p>Romeo then acknowledges the content-remove request:</p>
    <example caption="Initiator acknowledges content-remove"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='remove1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>Because the parties have chosen the Jingle ICE-UDP Transport Method, the initiator and responder exchange an open-ended number of possible candidate transports, perform connectivity checks, and agree upon a candidate transport as explained in <cite>XEP-0176</cite>. Once ICE negotiation is completed, the initiator sends a content-modify action to the responder.</p>
    <example caption="Initiator requests content-modify"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='mod1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-modify'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        [ ... ]
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1694498815'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   rel-addr='10.0.1.1'
                   rel-port='8998'
                   rem-addr='192.0.2.1'
                   rem-port='3478'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>The responder then acknowledges the content-modify action and sends a session-accept action.</p>
    <example caption="Responder acknowledges content-modify"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='mod1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends session-accept"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='accept1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-accept'
          initiator='romeo@montague.lit/orchard'
          responder='juliet@capulet.lit/balcony'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='0' name='PCMU' />
        <payload-type id='102' name='iLBC'/>
        <payload-type id='4' name='G723'/>
        <payload-type id='8' name='PCMA'/>
        <payload-type id='13' name='CN'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1694498815'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   rel-addr='10.0.1.1'
                   rel-port='8998'
                   rem-addr='192.0.2.1'
                   rem-port='3478'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>As above, if the payload types and transport candidate can be successfully used by both parties, then the initiator acknowledges the session-accept action.</p>
    <example caption="Initiator acknowledges session-accept"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='accept1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>The parties now begin to exchange media. In this case they would exchange audio using the Speex codec at a clockrate of 8000 since that is the highest-priority codec for the responder (as determined by the XML order of the &PAYLOADTYPE; children).</p>
    <p>The parties chat for a while. Eventually Juliet wants to get her hair in order so she puts Romeo on hold.</p>
    <example caption="Responder sends hold message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='hold1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <hold xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Initiator acknowledges hold message"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='hold1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>Juliet returns so she informs Romeo that she is actively engaged in the call again.</p>
    <example caption="Responder sends active message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='active1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <active xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Initiator acknowledges active message"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='active1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>The parties now continue the audio chat.</p>
    <p>Finally Juliet decides that she is presentable for a video chat so she sends a content-add request to Romeo.</p>
    <example caption="Responder sends a content-add"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='add1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-add'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='responder' name='video-is-back' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0180.html#ns'>
        <payload-type id='96' name='theora' height='720' width='1280'>
          <parameter name='delivery-method' value='inline'/>
          <parameter name='configuration' value='somebase16string'/>
          <parameter name='sampling' value='YCbCr-4:2:2'/>
        </payload-type>
        <payload-type id='32' name='MPV' clockrate='90000'/>
        <payload-type id='33' name='MP2T' clockrate='90000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>The entity receiving the content-add request then acknowledges the request and, if it is acceptable, returns a content-accept:</p>
    <example caption="Initiator acknowledges content-add"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='add1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <example caption="Initiator accepts content type definition"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='add2'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-accept'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='responder' name='video-is-back' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0180.html#ns'>
        <payload-type id='96' name='theora' height='720' width='1280'>
          <parameter name='delivery-method' value='inline'/>
          <parameter name='configuration' value='somebase16string'/>
          <parameter name='sampling' value='YCbCr-4:2:2'/>
        </payload-type>
        <payload-type id='32' name='MPV' clockrate='90000'/>
        <payload-type id='33' name='MP2T' clockrate='90000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>The other party then acknowledges the acceptance.</p>
    <example caption="Responder acknowledges content-accept"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='add2'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <p>The media session proceeds. Now they would exchange both audio and video, where the audio is exchanged the Speex codec at a clockrate of 8000 and the video is exchanged using the Theora codec with a height of 720 pixels, a width of 1280 pixels, and so on.</p>
    <p>The parties may continue the session as long as desired.</p>
    <p>Eventually, one of the parties terminates the session.</p>
    <example caption="Initiator sends session-terminate"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='term1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-terminate'
          initiator='romeo@montague.lit/orchard'
          reasoncode='no-error'
          reasontext='I&apos;m outta here!'
          sid='a73sjjvkla37jfea'/>
</iq>
    ]]></example>
    <example caption="Responder acknowledges session-terminate"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='term1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
  </section2>
  <section2 topic='Secure Jingle Audio via UDP/TLS/RTP/SAVP, Negotiated with ICE-UDP' anchor='scenarios-secure'>
    <p>In this scenario, Romeo initiates a voice chat with Juliet using a transport method of ICE-UDP and an unencrypted profile of "RTP/AVP", but Juliet wants to chat securely so she requests the use of a secure transport as specified in &sdpdtls; (via a profile of "UDP/TLS/RTP/SAVP").</p>
    <p>The session flow is as follows:</p>
    <code><![CDATA[
Romeo                         Juliet
  |                             |
  |   session-initiate          |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-info (ringing)    |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   content-modify            |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   content-accept            |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   transport-info (X times)  |
  |   (with acks)               |
  |<--------------------------->|
  |   STUN connectivity checks  |
  |<--------------------------->|
  |   content-modify            |
  |---------------------------->|
  |   ack                       |
  |<----------------------------|
  |   session-accept            |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |   AUDIO (RTP)               |
  |<===========================>|
  |   session-terminate         |
  |<----------------------------|
  |   ack                       |
  |---------------------------->|
  |                             |
    ]]></code>
    <p>The protocol flow is as follows.</p>
    <example caption="Initiator sends session-initiate"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='jingle1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-initiate'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='96' name='speex' clockrate='16000'/>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='103' name='L16' clockrate='16000' channels='2'/>
        <payload-type id='98' name='x-ISAC' clockrate='8000'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
    </content>
  </jingle>
</iq>
    ]]></example>
    <example caption="Responder acknowledges session-initiate"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='jingle1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends ringing message"><![CDATA[
<iq from='juliet@capulet.com/balcony'
    id='ringing1'
    to='romeo@montague.net/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-info'
          initiator='romeo@montague.net/orchard'
          sid='a73sjjvkla37jfea'>
    <ringing xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'/>
  </jingle>
</iq>
    ]]></example>
    <example caption="Initiator acknowledges ringing message"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='ringing1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>However, Juliet wants to make sure that the communications are encrypted, so she sends a "content-modify" request to Romeo.</p>
    <example caption="Responder requests content-modify"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='mod1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-modify'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='responder'
             name='this-is-the-audio-content'
             profile='UDP/TLS/RTP/SAVP'/>
  </jingle>
</iq>
    ]]></example>
    <p>Romeo then acknowledges the content-modify request and, if it is acceptable, returns a content-accept:</p>
    <example caption="Initiator acknowledges content-modify"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='mod1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <example caption="Initiator accepts content definition"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='mod2'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-accept'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='responder' name='this-is-the-audio-content' profile='UDP/TLS/RTP/SAVP'/>
  </jingle>
</iq>
    ]]></example>
    <p>The other party then acknowledges the acceptance.</p>
    <example caption="Responder acknowledges content-accept"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='mod2'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <p>Because the parties have chosen the Jingle ICE-UDP Transport Method, the initiator and responder exchange an open-ended number of possible candidate transports, perform connectivity checks, and agree upon a candidate transport as explained in <cite>XEP-0176</cite>. Once ICE negotiation is completed, the initiator sends a content-modify action to the responder.</p>
    <example caption="Initiator requests content-modify"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='mod1'
    to='juliet@capulet.lit/balcony'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='content-modify'
          initiator='romeo@montague.lit/orchard'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        [ ... ]
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1694498815'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   rel-addr='10.0.1.1'
                   rel-port='8998'
                   rem-addr='192.0.2.1'
                   rem-port='3478'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>The responder then acknowledges the content-modify action and sends a session-accept action.</p>
    <example caption="Responder acknowledges content-modify"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='mod1'
    to='romeo@montague.lit/orchard'
    type='result'/>
    ]]></example>
    <example caption="Responder sends session-accept"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='accept1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-accept'
          initiator='romeo@montague.lit/orchard'
          responder='juliet@capulet.lit/balcony'
          sid='a73sjjvkla37jfea'>
    <content creator='initiator' name='this-is-the-audio-content' profile='UDP/TLS/RTP/SAVP'>
      <description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
        <payload-type id='97' name='speex' clockrate='8000'/>
        <payload-type id='18' name='G729'/>
        <payload-type id='0' name='PCMU' />
        <payload-type id='102' name='iLBC'/>
        <payload-type id='4' name='G723'/>
        <payload-type id='8' name='PCMA'/>
        <payload-type id='13' name='CN'/>
      </description>
      <transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
        <candidate component='1'
                   foundation='1'
                   generation='0'
                   ip='192.0.2.3'
                   network='1'
                   port='45664'
                   priority='1694498815'
                   protocol='udp'
                   pwd='asd88fgpdd777uzjYhagZg'
                   rel-addr='10.0.1.1'
                   rel-port='8998'
                   rem-addr='192.0.2.1'
                   rem-port='3478'
                   type='srflx'
                   ufrag='8hhy'/>
      </transport>
    </content>
  </jingle>
</iq>
    ]]></example>
    <p>If the payload types and transport candidate can be successfully used by both parties, then the initiator acknowledges the session-accept action.</p>
    <example caption="Initiator acknowledges session-accept"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='accept1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
    <p>The parties now begin to exchange media. In this case they would exchange audio using the Speex codec at a clockrate of 8000 since that is the highest-priority codec for the responder (as determined by the XML order of the &PAYLOADTYPE; children).</p>
    <p>The parties may continue the session as long as desired.</p>
    <p>Eventually, one of the parties terminates the session.</p>
  <example caption="Responder terminates the session"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
    id='term1'
    to='romeo@montague.lit/orchard'
    type='set'>
  <jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
          action='session-terminate'
          initiator='romeo@montague.lit/orchard'
          reasoncode='no-error'
          reasontext='Sorry, gotta go!'
          sid='a73sjjvkla37jfea'/>
</iq>
    ]]></example>
    <p>The other party then acknowledges termination of the session:</p>
    <example caption="Initiator acknowledges termination"><![CDATA[
<iq from='romeo@montague.lit/orchard'
    id='term1'
    to='juliet@capulet.lit/balcony'
    type='result'/>
    ]]></example>
  </section2>
</section1>

<section1 topic='Implementation Notes' anchor='impl'>
  <section2 topic='Codecs' anchor='impl-codecs'>
    <p>Support for the Speex codec is RECOMMENDED.</p>
  </section2>
  <section2 topic='DTMF' anchor='impl-dtmf'>
    <p>If it is necessary to send Dual Tone Multi-Frequency (DTMF) tones, it is REQUIRED to use the XML format specified &xep0181;.</p>
  </section2>
  <section2 topic='When to Listen' anchor='impl-listen'>
    <p>When the Jingle Audio content type is accepted via a "content-accept" action, both initiator and responder SHOULD start listening for audio as defined by the negotiated transport method and audio application format. For interoperability with telephony systems, after the responder acknowledges the session initiation request, the responder SHOULD send a "ringing" message and both parties SHOULD play any audio received.</p>
  </section2>
</section1>

<section1 topic='Security Considerations' anchor='security'>
  <p>In order to secure the data stream, implementations SHOULD use encryption methods appropriate to the transport method and media being exchanged; for example, in the case of UDP, that would include Datagram Transport Layer Security (DTLS) as specified in &rfc4347;. The work-in-progress <cite>draft-fishl-mmusic-sdp-dtls</cite> defines such methods for the Session Description Protocol; the relevant RTP profile (e.g., "UDP/TLS/RTP/SAVP" for transporting the RTP stream over DTLS with UDP) shall be specified as the value of the &CONTENT; element's 'profile' attribute.</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:</p>
    <ul>
      <li>http://www.xmpp.org/extensions/xep-0167.html#ns</li>
      <li>http://www.xmpp.org/extensions/xep-0167.html#ns-errors</li>
      <li>http://www.xmpp.org/extensions/xep-0167.html#ns-info</li>
    </ul>
    <p>Upon advancement of this specification, the &REGISTRAR; shall issue permanent namespaces in accordance with the process defined in Section 4 of &xep0053;.</p>
    <p>The following namespaces are requested, and are thought to be unique per the XMPP Registrar's requirements:</p>
    <ul>
      <li>urn:xmpp:jingle:app:audio-rtp</li>
      <li>urn:xmpp:jingle:app:audio-rtp:errors</li>
      <li>urn:xmpp:jingle:app:audio-rtp:info</li>
    </ul>
  </section2>
  <section2 topic='Jingle Application Formats' anchor='registrar-content'>
    <p>The XMPP Registrar shall include "audio-rtp" in its registry of Jingle application formats. The registry submission is as follows:</p>
    <code><![CDATA[
<application>
  <name>audio-rtp</name>
  <desc>Jingle sessions that support audio exchange via the Real-time Transport Protocol</desc>
  <transport>lossy</transport>
  <doc>XEP-0167</doc>
</application>
    ]]></code>
  </section2>
</section1>

<section1 topic='XML Schemas' anchor='schema'>
  <section2 topic='Application Format' anchor='schema-content'>
    <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-0167.html#ns'
    xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'
    elementFormDefault='qualified'>

  <xs:element name='description'>
    <xs:complexType>
      <xs:sequence minOccurs='0' maxOccurs='unbounded'/>
        <xs:element ref='payload-type'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name='payload-type'>
    <xs:complexType>
      <xs:sequence minOccurs='0' maxOccurs='unbounded'>
        <xs:element ref='parameter'/>
      </xs:sequence>
      <xs:attribute name='channels' type='xs:byte' use='optional' default='1'/>
      <xs:attribute name='clockrate' type='xs:short' use='optional'/>
      <xs:attribute name='id' type='xs:unsignedByte' use='required'/>
      <xs:attribute name='maxptime' type='xs:short' use='optional'/>
      <xs:attribute name='name' type='xs:string' use='optional'/>
      <xs:attribute name='ptime' type='xs:short' use='optional'/>
    </xs:complexType>
  </xs:element>

  <xs:element name='parameter'>
    <xs:complexType>
      <xs:simpleContent>
        <xs:extension base='empty'>
          <xs:attribute name='name' type='xs:string' use='required'/>
          <xs:attribute name='value' type='xs:string' 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>
  </section2>
  <section2 topic='Informational Messages' anchor='schema-info'>
    <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-0167.html#ns-info'
    xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns-info'
    elementFormDefault='qualified'>

  <xs:element name='active' type='empty'/>
  <xs:element name='hold' type='empty'/>
  <xs:element name='mute' type='empty'/>
  <xs:element name='ringing' type='empty'/>

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

</xs:schema>
    ]]></code>
  </section2>
</section1>
</xep>