<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 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>
<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>Note: The Raw UDP transport does not provide traversal of Network Address Translators (NATs); if NAT traversal is needed, &xep0176; SHOULD be used. 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 may work in some circumstances. The method can therefore be thought of as the Jingle equivalent of the "I'm Feeling Lucky" button; it is also helpful for use in unit-testing of Jingle implementation by developers working on a local network (see &xep0208;).</p>
<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 <linkurl='#protocol'>Protocol Description</link> section of this document.</p></li>
<li><p>The semantics of the &DESCRIPTION; element are defined in the <linkurl='#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>
<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 <linkurl='#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>
<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 "default" candidate as described in Section 4.1.3 of &ice;. 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>
<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>
<p>The responder MUST immediately attempt to send data to the IP and port specified in the initiation request. If all goes well, the data will be received by the initiator and media will flow. Because delivery of UDP data is not acknowledged, a party that receives media SHOULD send an informational message of <received/> to the other party as specified below.</p>
<p>As noted, 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>
<p>Naturally, the initiator SHOULD also attend to send media to the responder as specified above. This media too may or may not get through, but if it does then the other party should acknowledge receipt.</p>
<p>When it attempts to send data to a Raw UDP candidate, a party SHOULD send an informational message of <trying/>. If a party receives data, it SHOULD send an informational message of <received/>.</p>
<p>Each 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 <linkurl='#info'>Informational Messages</link> section of this document.</p>
<p>Informational messages MAY be sent by the either party within the context of the Raw UDP transport to communicate whether the party has attempted to send media or has received media. 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 &NSNOTE;. The following payload elements are defined:</p>
<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>
<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>
<examplecaption="Service Discovery information request"><