<abstract>This specification defines a Jingle transport method that results in sending media data using raw datagram associations via the User Datagram Protocol (UDP). This simple transport method does not provide NAT traversal, and the ICE-UDP transport method should be used if NAT traversal is required.</abstract>
<li>Because the removal of the <trying/> info message is backwards-incompatible, modified protocol version number from 0 to 1 and changed namespace from urn:xmpp:jingle:transports:raw-udp:0 to urn:xmpp:jingle:transports:raw-udp:1.</li>
<remark><p>For consistency with the ICE-UDP transport method, added component attribute to handle RTCP candidates and allowed multiple <candidate/> child elements.</p></remark>
<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>
<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>
<remark><p>Removed candidate element and specified exchange of address information via transport-info messages; clarified usage of name attribute.</p></remark>
<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 application 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) association (see &rfc0768;). This "raw-udp" method results in a datagram transport method suitable for use in media applications where some packet loss is tolerable (e.g., audio and video).</p>
<p>The Raw UDP transport does not provide end-to-end traversal of Network Address Translators (NATs), or even basic connectivity checks; if NAT traversal is needed, Jingle clients SHOULD use &ice; as described in &xep0176;. The Raw UDP transport method is defined only for the purpose of specifying the IP address and port that an entity considers "most likely to succeed" and is a "hit-or-miss" method that might work end-to-end in some circumstances (especially when the sending entity is a gateway or relay, for example when a back-to-back user agent or call manager sends an early media offer to the initiator on behalf of the responder, as described in &xep0167;).</p>
<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>
<p>In accordance with Section 10 of <cite>XEP-0166</cite>, this document specifies the following information related to the Jingle Raw UDP transport type:</p>
<li><p>Successful negotiation of the Raw UDP method results in use of a datagram 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 in the context of the Real-time Transport Protocol (RTP; see &rfc3550;), the component numbered "1" shall be associated with RTP and the component numbered "2" shall be associated with the Real Time Control Protocol (RTCP).</p></li>
<p>In order for the initiator in a Jingle exchange to start the negotiation, it sends a Jingle "session-initiate" stanza that includes at least one content type, as described in <cite>XEP-0166</cite>. 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 'urn:xmpp:jingle:transports:raw-udp:1' namespace &VNOTE;, 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 'id' attributes of the &CANDIDATE; element. The &TRANSPORT; element MAY include more than one &CANDIDATE; element (typically one for RTP and another for RTCP).</p>
<p>All attributes are REQUIRED. The 'ip' and 'port' attributes are self-explanatory. The 'component' attribute enables the parties to distinguish between different aspects of the media stream that each need to use a separate transport address (e.g., RTP and RTCP). The 'generation' attribute defines 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). The 'id' attribute uniquely identifies this candidate for tracking purposes.</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 "default" candidate as described in the ICE specification. 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 sender needs to 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>
<p>As soon as the responder acknowledges the session initiation request, it MUST send a Jingle session-accept to the initiator. This session-accept message MAY include another Raw UDP candidate generated by the responder; alternativey, the responder MAY send this in a Jingle transport-info message.</p>
<examplecaption="Responder definitively accepts the session"><