<abstract>This document defines a Jingle transport method that results in sending data between two entities using Interactive Connectivity Establishment (ICE) methodology.</abstract>
<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 (session) types, leaving that up to separate specifications. The current document defines a transport method for establishing and managing data connections between XMPP entities, using the &ice; methodology currently being developed within the IETF.</p>
<p>The process for ICE negotiation is largely the same in Jingle as it is in draft-ietf-mmusic-ice. There are several differences:</p>
<ul>
<li>Instead of using SIP as the signalling channel, Jingle uses XMPP as the signalling channel.</li>
<li>In Jingle, each candidate transport is sent in a separate IQ exchange (rather than sending all candidates at once as in draft-ietf-mmusic-ice); this approach takes advantage of the request-response semantics of the XMPP &IQ; stanza type and enables the parties to send higher-priority candidates earlier in the negotiation.</li>
<li>Syntax from the Session Description Protocol (see &rfc4566;) is mapped to an XML syntax suitable for sending over the XMPP signalling channel.</li>
<p><em>Note: This document depends on the IETF's Interactive Connectivity Establishment (ICE) specification, which is a work in progress. Every effort has been made to keep this document synchronized with draft-ietf-mmusic-ice, for which the latest published version is 10 (hereafter referred to as "&ice10;"). The interested reader is referred to the &ice10; for a detailed description of the ICE methodology, which for the most part this document merely maps to XMPP syntax.</em></p>
<p>The Jingle transport method defined herein is designed to meet the following requirements:</p>
<ol>
<li>Make it possible to establish and manage out-of-band connections between two XMPP entities, even if they are behind Network Address Translators (NATs) or firewalls.</li>
<li>Make it relatively easy to implement support in standard Jabber/XMPP clients.</li>
<li>Where communication with non-XMPP entities is needed, push as much complexity as possible onto server-side gateways between the XMPP network and the non-XMPP network.</li>
</ol>
</section1>
<section1topic='Glossary'anchor='terms'>
<p>The reader is referred to draft-ietf-mmusic-ice for a description of various terms used in the context of ICE. Those terms are not reproduced here.</p>
<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 transport method. If the initiator wishes to negotiate the ICE transport, it MUST include an empty &TRANSPORT; child element qualified by the 'http://jabber.org/protocol/jingle/transport/ice' namespace.</p>
<p>If the responder provisionally accepts the session initiation request as shown above, both initiator and responder MUST immediately negotiate connectivity over the ICE transport by exchanging XML-formatted candidate transports for the channel. This negotiation proceeds immediately in order to maximize the possibility that media can be exchanged as quickly as possible. <note>Concurrent with negotiation of the ICE candidates, it is possible for the initiator and responder to negotiate which content types the session will include, which transport methods will be tried for each content type, etc. Those negotiation flows are shown in <cite>XEP-0166</cite>. This document specifies only negotiation of the ICE transport method.</note></p>
<p>The attributes of the <candidate/> element are described in the following table:</p>
<tablecaption='Candidate Attributes'>
<tr>
<th>Name</th>
<th>Description</th>
<th>SDP Syntax</th>
<th>Example</th>
</tr>
<tr>
<td>component</td>
<td>A Component ID as defined in &ice10;</td>
<td>Component ID value in a=candidate line</td>
<td>1</td>
</tr>
<tr>
<td>foundation</td>
<td>A Foundation as defined in &ice10;</td>
<td>Foundation value in a=candidate line</td>
<td>1</td>
</tr>
<tr>
<td>generation</td>
<td>An index, starting at 0, that enables the parties to keep track of updates to the candidate throughout the life of the session</td>
<td>N/A</td>
<td>0</td>
</tr>
<tr>
<td>ip</td>
<td>The Internet Protocol (IP) address for the candidate transport mechanism; this may be either an IPv4 address or an IPv6 address</td>
<td>IP Address value in a=candidate line</td>
<td>10.0.1.1</td>
</tr>
<tr>
<td>network</td>
<td>An index, starting at 0, referencing which network this candidate is on for a given peer (used for diagnostic purposes if the calling hardware has more than one Network Interface Card or NIC)</td>
<td>N/A</td>
<td>0</td>
</tr>
<tr>
<td>port</td>
<td>The port at the candidate IP address</td>
<td>Port value in a=candidate line</td>
<td>8998</td>
</tr>
<tr>
<td>priority</td>
<td>A Priority as defined in &ice10;</td>
<td>Priority value in a=candidate line</td>
<td>9909</td>
</tr>
<tr>
<td>protocol</td>
<td>The protocol to be used; allowable values are: "udp" (when standard &ice10; is used); "tcp", "tcp-act", and "tcp-pass" (when &ice-tcp; is used); and "ssltcp" (definition to follow)</td>
<td>a=ice-ufrag line</td>
<td>udp</td>
</tr>
<tr>
<td>pwd</td>
<td>A Password as defined in &ice10;</td>
<td>a=ice-pwd line</td>
<td>asd88fgpdd777uzjYhagZg</td>
</tr>
<tr>
<td>type</td>
<td>A Candidate Type as defined in &ice10;; the allowable values are "host" for host candidates, "srflx" for server reflexive candidates, "prflx" for peer reflexive candidates, and "relay" for relayed candidates</td>
<p>The first step in negotiating connectivity is for each client to immediately begin sending candidate transport methods to the other client. These candidates SHOULD be gathered by following the procedure specified in Section 4.1 of &ice10; and prioritized by following the procedure specified in Section 4.2 of &ice10;. Each candidate MUST be sent in a &JINGLE; element with an action of "transport-info".</p>
<p>If the responder receives and can successfully process a given candidate, it returns an IQ-result (if not, for example because the candidate data is improperly formatted, it returns an error).</p>
<p>Note well that the responder is only indicating receipt of the candidate, not telling the initiator that the candidate will be used.</p>
<p>The initiator keeps sending candidates, one after the other (without stopping to receive an acknowledgement of receipt from the responder for each candidate) until it has exhausted its supply of possible or desirable candidate transports. (Because certain candidates may be more "expensive" in terms of bandwidth or processing power, the initiator may not want to advertise their existence unless necessary.) For each candidate, the responder acknowledges receipt.</p>
<p>At the same time (i.e., immediately after provisionally accepting the session, not waiting for the initiator to begin or finish sending candidates), the responder also begins sending candidates that may work for it. As above, the initiator acknowledges receipt of the candidates.</p>
<p>As the initiator and responder receive candidates, they probe the various candidate transports for connectivity. In performing these connectivity checks, client SHOULD follow the procedure specified in Section 7 of &ice10;.</p>
<examplecaption="Initiating Entity Sends a Candidate"><