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xep-0293.xml 15KB

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  1. <?xml version='1.0' encoding='UTF-8'?>
  2. <!DOCTYPE xep SYSTEM 'xep.dtd' [
  3. <!ENTITY % ents SYSTEM 'xep.ent'>
  4. %ents;
  5. ]>
  6. <?xml-stylesheet type='text/xsl' href='xep.xsl'?>
  7. <xep>
  8. <header>
  9. <title>Jingle RTP Feedback Negotiation</title>
  10. <abstract>This specification defines an XMPP extension to negotiate
  11. the use of the Extended RTP Profile for Real-time Transport Control
  12. Protocol (RTCP)-Based Feedback (RTP/AVPF) with Jingle RTP
  13. sessions</abstract>
  14. &LEGALNOTICE;
  15. <number>0293</number>
  16. <status>Draft</status>
  17. <type>Standards Track</type>
  18. <sig>Standards</sig>
  19. <approver>Council</approver>
  20. <dependencies>
  21. <spec>XEP-0167</spec>
  22. <spec>RFC 4585</spec>
  23. </dependencies>
  24. <supersedes/>
  25. <supersededby/>
  26. <shortname>NOT_YET_ASSIGNED</shortname>
  27. <schemaloc>
  28. <url>http://xmpp.org/schemas/jingle-apps-rtp-rtcp-fb.xsd</url>
  29. </schemaloc>
  30. <discuss>jingle</discuss>
  31. <author>
  32. <firstname>Olivier</firstname>
  33. <surname>Crête</surname>
  34. <email>olivier.crete@collabora.co.uk</email>
  35. <jid>olivier.crete@collabora.co.uk</jid>
  36. </author>
  37. <revision>
  38. <version>1.0</version>
  39. <date>2015-08-11</date>
  40. <initials>XEP Editor (mam)</initials>
  41. <remark><p>Advanced to Draft per a vote of the XMPP Council.</p></remark>
  42. </revision>
  43. <revision>
  44. <version>0.3</version>
  45. <date>2015-04-29</date>
  46. <initials>ph</initials>
  47. <remark><p>Address council LC feedback.</p></remark>
  48. </revision>
  49. <revision>
  50. <version>0.2</version>
  51. <date>2015-03-25</date>
  52. <initials>ph</initials>
  53. <remark><p>Added XML Schema; Updated based on last-call feedback.</p></remark>
  54. </revision>
  55. <revision>
  56. <version>0.1</version>
  57. <date>2011-03-24</date>
  58. <initials>psa</initials>
  59. <remark><p>Initial published version.</p></remark>
  60. </revision>
  61. <revision>
  62. <version>0.0.1</version>
  63. <date>2011-01-10</date>
  64. <initials>oc</initials>
  65. <remark><p>First draft.</p></remark>
  66. </revision>
  67. </header>
  68. <section1 topic='Introduction' anchor='introduction'>
  69. <p>This documents specifies how to negotiate the use of the Extended
  70. RTP Profile for Real-time Transport Control Protocol (RTCP)-Based
  71. Feedback (RTP/AVPF) with Jingle RTP sessions.</p>
  72. </section1>
  73. <section1 topic='Requirements' anchor='requirements'>
  74. <p>The Jingle extension defined herein is designed to meet the following requirements:</p>
  75. <ol>
  76. <li>Enable negotiations of the required parameters for the
  77. transmissions of RTP Feedback messages as defined in &rfc4585;.</li>
  78. <li>Map these parameters to Session Description Protocol (SDP; see
  79. &rfc4566;) to enable interoperability.</li>
  80. </ol>
  81. </section1>
  82. <section1 topic='New elements' anchor='elements'>
  83. <p>This specification defines two new elements, &lt;rtcp-fb/&gt; and
  84. &lt;rtcp-fb-trr-int/&gt;, that can be inserted in the
  85. &lt;description/&gt; or the &lt;payload-type/&gt; elements of
  86. &xep0167;. The presence of any of these elements in a
  87. content's description means that the RTP/AVPF profile should be used
  88. for the whole content. If any of these elements are inside the
  89. &lt;payload-type/&gt; element, the parameters specified apply only to
  90. that payload type, if they are directly inside the
  91. &lt;description/&gt; tag, then the specified parameters apply to the
  92. whole content.</p>
  93. <p>The attributes of the &lt;rtcp-fb/&gt; element are:</p>
  94. <table caption='rtcp-fb attributes'>
  95. <tr>
  96. <th>Attribute</th>
  97. <th>Description</th>
  98. <th>Inclusion</th>
  99. <th>Possible values</th>
  100. </tr>
  101. <tr>
  102. <td>type</td>
  103. <td>The type of feedback</td>
  104. <td>REQUIRED</td>
  105. <td>ack, nack, ccm, app, etc..</td>
  106. </tr>
  107. <tr>
  108. <td>subtype</td>
  109. <td>The subtype (depends on the type)</td>
  110. <td>OPTIONAL (possibly REQUIRED depending on the type)</td>
  111. <td>
  112. ack: rpsi, app;
  113. nack: sli, pli, rpsi, app, rai;
  114. ccm: fir, tmmbr, tstr, vbcm;
  115. app: depends on the application;
  116. </td>
  117. </tr>
  118. </table>
  119. <p>Any type or subtype of feedback message that requires extra
  120. parameters in the a=b form can use the &lt;parameter/&gt; element to
  121. describe it. Any other form of parameter can be stored as the 'key' attribute in a parameter element with an empty value.</p>
  122. <p>Note: this overlaps with the subtype attribute. If there is only one parameter, use the subtype. The only known example where this is required is ccm.</p>
  123. <p>The element &lt;rtcp-fb-trr-int/&gt; is used to specify the minimum
  124. interval between two Regular (full compound) RTCP packets in
  125. milliseconds for this media session. It corresponds to the
  126. "a=rtcp-fb:* trr-int" line in SDP. The attributes of the
  127. &lt;rtcp-fb-trr-int/&gt; element are:</p>
  128. <table caption='rtcp-fb-trr-int attributes'>
  129. <tr>
  130. <th>Attribute</th>
  131. <th>Description</th>
  132. <th>Inclusion</th>
  133. <th>Possible values</th>
  134. </tr>
  135. <tr>
  136. <td>value</td>
  137. <td>Number of milliseconds between regular RTCP reports</td>
  138. <td>REQUIRED</td>
  139. <td>0 to MAXUINT (default to 0)</td>
  140. </tr>
  141. </table>
  142. </section1>
  143. <section1 topic='Negotiation' anchor='negotiation'>
  144. <p>Feedback messages are negotiated along side the codecs. They follow
  145. the same Offer/Answer mechanism based on SDP Offer/Answer. The
  146. initiator signals which feedback messages it wants to send or
  147. receive in the the &lt;session-initiate/&gt; iq stanza. If the
  148. responder does not understand the type or subtype of a feedback
  149. message, it MUST remove the element from the reply. If the responder
  150. does not wish to provide or receive some kind of feedback, it MUST
  151. remove the relevant element. It MUST then send the remaining
  152. elements it wants to keep as-is without modifying them in the
  153. &lt;session-accept/&gt;</p>
  154. <p>To conform with the negotiation rules outlined in <cite>RFC 4585</cite> Section 4,
  155. the responder MUST send any &lt;rtcp-fb/&gt; element as-is if it
  156. accepts it. It MUST NOT change any parameter. It MUST NOT add any
  157. &lt;rtcp-fb/&gt; element that was not offered by the initiator. It
  158. MUST NOT modify the 'value' of any &lt;rtcp-fb-trr-int/&gt;
  159. element. It can only remove the &lt;rtcp-fb-trr-int/&gt; element or
  160. reject the content. If all the feedback messages are removed but the
  161. responder wants to stay in the RTP/AVPF profile, it MUST put a
  162. &lt;rtcp-fb-trr-int/&gt; element with the same 'value' that it
  163. received from the intiator, if the initiator did not provide a
  164. &lt;rtcp-fb-trr-int/&gt; element, then this value is "0".</p>
  165. <p>Example negotiation where the initiator requests Packet Loss
  166. Indications (pli) as defined in <cite>RFC 4585</cite> on both H.263 and H.264,
  167. but also requests Slice Loss Indications for H.264 with a minimum
  168. interval between regular full compound RTCP packets of 100 milliseconds.</p>
  169. <example caption='Initiator sends description inside session-initiate'><![CDATA[
  170. <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
  171. <rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack' subtype='pli'/>
  172. <payload-type id='96' name='H264' clockrate='90000'>
  173. <rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='100'/>
  174. <rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack' subtype='sli'/>
  175. </payload-type>
  176. <payload-type id='34' name='H263' clockrate='90000'/>
  177. </description>
  178. ]]></example>
  179. <p>Example reply where the responder rejects the "sli" but
  180. accepts the "pli".</p>
  181. <example caption='Responder sends description inside session-accept'><![CDATA[
  182. <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
  183. <rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack' subtype='pli'/>
  184. <payload-type id='96' name='H264' clockrate='90000'>
  185. <rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='100'/>
  186. </payload-type>
  187. <payload-type id='34' name='H263' clockrate='90000'/>
  188. </description>
  189. ]]></example>
  190. <p>Another reply to the same request where the responder wishes to
  191. stay in the AVPF profile but rejects all specific feedback messages
  192. by using the &lt;rtcp-fb-trr-int/&gt; with the default value.</p>
  193. <example caption='Responder sends description inside session-accept without any feedback message'><![CDATA[
  194. <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
  195. <rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='0'/>
  196. <payload-type id='96' name='H264' clockrate='90000'/>
  197. <payload-type id='34' name='H263' clockrate='90000'/>
  198. </description>
  199. ]]></example>
  200. </section1>
  201. <section1 topic='Mapping to Session Description Protocol' anchor='sdp-mapping'>
  202. <p>The &lt;rtcp-fb/&gt; element maps to the a:rtcp-fb= SDP line with
  203. the exception of the 'trr-int' parameter which is mapped into it's
  204. own element (&lt;rtcp-fb-trr-int/&gt;) in XMPP. The payload types
  205. are also not explicitly written in the &lt;rtcp-fb/&gt; and
  206. &lt;rtcp-fb-trr-int/&gt; elements. Instead, each payload type has its own
  207. set of &lt;rtcp-fb/&gt; and &lt;rtcp-fb-trr-int/&gt; elements if
  208. they do not apply to the whole content.</p>
  209. <p>Example conversion of a sample fragment of a SDP containing an
  210. audio session using the RTP/AVP profile for audio and the RTP/AVPF
  211. profile for video:</p>
  212. <example caption='SDP fragment'><![CDATA[
  213. v=0
  214. o=remeo 3203093520 3203093520 IN IP4 host.example.com
  215. s=Video call with feedback
  216. t=3203130148 3203137348
  217. m=audio 49170 RTP/AVP 0
  218. c=IN IP4 10.0.1.1
  219. a=rtpmap:0 PCMU/8000
  220. m=video 59172 RTP/AVPF 98 99
  221. c=IN IP4 10.0.1.1
  222. a=rtpmap:98 H263-1998/90000
  223. a=rtpmap:99 H261/90000
  224. a=rtcp-fb:* nack
  225. a=rtcp-fb:98 nack rpsi
  226. a=rtcp-fb:98 trr-int 100
  227. ]]></example>
  228. <example caption='The same description in XMPP format'><![CDATA[
  229. <iq from='romeo@montague.lit/orchard'
  230. id='ph37a419'
  231. to='juliet@capulet.lit/balcony'
  232. type='set'>
  233. <jingle xmlns='urn:xmpp:jingle:1'>
  234. action='session-initiate'
  235. initiator='romeo@montague.lit/orchard'
  236. sid='a73sjjvkla37jfea'>
  237. <content creator='initiator' name='voice'>
  238. <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'>
  239. <payload-type id='0' name='PCMU' />
  240. </description>
  241. <transport xmlns='urn:xmpp:jingle:transports:raw-udp:1'>
  242. <candidate component='1'
  243. generation='0'
  244. id='a9j3mnbtu1'
  245. ip='10.0.1.1'
  246. port='49170'/>
  247. <candidate component='2'
  248. generation='0'
  249. id='a9j3mnbtu1'
  250. ip='10.0.1.1'
  251. port='49171'/>
  252. </transport>
  253. </content>
  254. <content creator='initiator' name='face'>
  255. <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
  256. <rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack'/>
  257. <payload-type id='98' name='H263-1998'>
  258. <rtcp-fb xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' type='nack'
  259. subtype='rpsi'/>
  260. <rtcp-fb-trr-int xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0' value='100'/>
  261. </payload-type>
  262. <payload-type id='99' name='H264' />
  263. </description>
  264. <transport xmlns='urn:xmpp:jingle:transports:raw-udp:1'>
  265. <candidate component='1'
  266. generation='0'
  267. id='a9j3mnbtu1'
  268. ip='10.0.1.1'
  269. port='49172'/>
  270. <candidate component='2'
  271. generation='0'
  272. id='a9j3mnbtu1'
  273. ip='10.0.1.1'
  274. port='49173'/>
  275. </transport>
  276. </content>
  277. </jingle>
  278. </iq>
  279. ]]></example>
  280. </section1>
  281. <section1 topic='Determining support' anchor='determining-support'>
  282. <p>To advertise its support for Extended RTCP Feedback in Jingle RTP
  283. Sessions and a minimum interval between regular RTCP packets, when
  284. replying to &xep0030; information requests an entity MUST return the
  285. following features:</p>
  286. <ol>
  287. <li>URNs for any version of this protocol that the entity
  288. supports -- e.g., "urn:xmpp:jingle:apps:rtp:rtcp-fb:0" for the
  289. current version</li>
  290. </ol>
  291. <p>An example follows:</p>
  292. <example caption="Service discovery information request"><![CDATA[
  293. <iq from='romeo@montague.lit/orchard'
  294. id='bh3vd715'
  295. to='juliet@capulet.lit/balcony'
  296. type='get'>
  297. <query xmlns='http://jabber.org/protocol/disco#info'/>
  298. </iq>
  299. ]]></example>
  300. <example caption="Service discovery information response"><![CDATA[
  301. <iq from='juliet@capulet.lit/balcony'
  302. id='bh3vd715'
  303. to='romeo@montague.lit/orchard'
  304. type='result'>
  305. <query xmlns='http://jabber.org/protocol/disco#info'>
  306. <feature var='urn:xmpp:jingle:1'/>
  307. <feature var='urn:xmpp:jingle:apps:rtp:1'/>
  308. <feature var='urn:xmpp:jingle:apps:rtp:video'/>
  309. <feature var='urn:xmpp:jingle:apps:rtp:rtcp-fb:0'/>
  310. </query>
  311. </iq>
  312. ]]></example>
  313. </section1>
  314. <section1 topic='IANA Considerations' anchor='iana-considerations'>
  315. <p>This document requires no interaction with the Internet Assigned
  316. Numbers Authority (IANA).</p>
  317. </section1>
  318. <section1 topic='XMPP Registrar Considerations' anchor='registrar'>
  319. <section2 topic='Protocol Namespaces' anchor='registrar-ns'>
  320. <p>This specification defines the following XML namespaces:</p>
  321. <ul>
  322. <li>urn:xmpp:jingle:apps:rtp:rtcp-fb:0</li>
  323. </ul>
  324. <p>The &REGISTRAR; includes the foregoing namespaces in its
  325. registry at &NAMESPACES;, as governed by &xep0053;.</p>
  326. </section2>
  327. <section2 topic='Namespace Versioning' anchor='registrar-versioning'>
  328. &NSVER;
  329. </section2>
  330. </section1>
  331. <section1 topic='XML Schemas'>
  332. <code><![CDATA[
  333. <?xml version='1.0' encoding='UTF-8'?>
  334. <xs:schema
  335. xmlns:xs='http://www.w3.org/2001/XMLSchema'
  336. targetNamespace='urn:xmpp:jingle:apps:rtp:rtcp-fb:0'
  337. xmlns='urn:xmpp:jingle:apps:rtp:rtcp-fb:0'
  338. elementFormDefault='qualified'>
  339. <xs:annotation>
  340. <xs:documentation>
  341. The protocol documented by this schema is defined in
  342. XEP-0293: http://www.xmpp.org/extensions/xep-0293.html
  343. </xs:documentation>
  344. </xs:annotation>
  345. <xs:element name='rtcp-fb'>
  346. <xs:complexType>
  347. <xs:sequence>
  348. <xs:element name='parameter'
  349. type='parameterElementType'
  350. minOccurs='0'
  351. maxOccurs='unbounded'/>
  352. </xs:sequence>
  353. <xs:attribute name='type' type='xs:string' use='required'/>
  354. <xs:attribute name='subtype' type='xs:string' use='optional'/>
  355. </xs:complexType>
  356. </xs:element>
  357. <xs:element name='rtcp-fb-trr-int'>
  358. <xs:complexType>
  359. <xs:simpleContent>
  360. <xs:extension base='empty'>
  361. <xs:attribute name='value' type='xs:positiveInteger' use='required'/>
  362. </xs:extension>
  363. </xs:simpleContent>
  364. </xs:complexType>
  365. </xs:element>
  366. <xs:complexType name='parameterElementType'>
  367. <xs:simpleContent>
  368. <xs:extension base='empty'>
  369. <xs:attribute name='name' type='xs:string' use='required'/>
  370. <xs:attribute name='value' type='xs:string' use='optional'/>
  371. </xs:extension>
  372. </xs:simpleContent>
  373. </xs:complexType>
  374. </xs:schema>
  375. ]]></code>
  376. </section1>
  377. <section1 topic='Acknowledgements' anchor='ack'>
  378. <p>Thanks to Youness Alaoui for his feedback.</p>
  379. </section1>
  380. </xep>