<abstract>This documents specifies how Jingle Clients can interact with Jingle Relay Nodes Services and how XMPP entities can provide, search and list available Jingle Relay Nodes.</abstract>
<p>Jingle Nodes is an XMPP Based Relay Service providing standard UDP/TCP Relay, but negotiated via XMPP. Jingle Relay Nodes are intend to provide easy to use Jingle Relay Type Candidates that can be used in ICE-UDP, RAW-UDP, TCP Jingle Sessions. Relay Candidates can provide NAT Traversal for Jingle users with or without STUN/TURN Support. The main benefits of Jingle Relay Nodes is the easy to use candidates, Jingle Clients can became a Node and Jingle Relay Nodes are published via XMPP, meaning every Client or Server can also act as a tracker of another Nodes and STUN Servers.</p>
<p>Jingle Relay Nodes MUST be binded directly to a Public IP address without firewall for traffic on the port range reserved to be used by relay candidates. This is the main and unique requirement for a peer provide Relay Nodes Service.
All signalling, request, response and publishing is done via XMPP, not requiring any extra stack or protocol in the Client or Server, for usage and discoveral of Nodes.</p>
<dd>Relays are mainly used to transfer traffic to servers located on a NAT:ed (masqueraded) network, where the IP addresses on the NAT:ed network cannot be accessed from the outside. When you use an IP address that is for local use only, you must use NAT and relays because these IP addresses cannot be accessed in any other way. Relays can also be used for non-NAT:ed networks.</dd>
</di>
<di>
<dt>Jingle Relay Node</dt>
<dd>Is an instance of a Relay Service that is negotiable via XMPP, following the procedures described on this Extension.</dd>
</di>
<di>
<dt>Tracker</dt>
<dd>Is the entity that trackers Jingle Relay Nodes and also publishes the list upon request. Potentially all Jingle Clients might act as a Node Tracker.</dd>
</di>
<di>
<dt>Channel</dt>
<dd>Is the UDP/TCP Relay Channel, provided by the a Jingle Relay Node. The channel act as a NAT Traversal Channel in order to delivery and receive media.</dd>
</di>
<di>
<dt>Requester</dt>
<dd>Is the Jingle Client that makes requests and make use of a Channel. The Requester receives a relay <linkurl="#transports">Transport Candidate</link> that can be used with &xep0176; or &xep0177;.</dd>
<p>In diagrams, the following conventions are used:</p>
<ul>
<li>Single-dashed lines (---) represent Jingle stanzas that are sent via the XMPP signalling channel.</li>
<li>Double-dashed lines (===) represent media packets that are sent via the data channel, which typically is not an XMPP channel (although the <cite>Jingle In-Band Bytestreams Transport Method</cite> is an exception) but instead is a direct or mediated channel between the endpoints.</li>
</ul>
</section2>
</section1>
<section1topic="Flow Example"anchor="rules">
<p>After the Jingle Clients gets succesfully connected to the XMPP Server, it MAY want to start discoverying available Relay Services in order to cache some entries. Having cached Relay Service Addresses is recommended as it speeds up the session setup time as the Client don't need to search for available Relay Services right before a session is started or received.</p>
<section2topic="Jingle Client Checks for Tracker or Relay Services on its own Server Domain"anchor="clientcheckownserver">
<p>A Jingle Client MAY start the search for Relay Services by querying his own XMPP Server Domain.</p>
<p>
<em>Note: This is a good implementation practice.</em>
<p><em>In this example 'montague.lit' XMPP Domain a Relay Service and a Tracker Service. The Relay Service can be contacted in order to retrieve Relay Channels. The Tracker Service can be contacted in order to retrieve its known services.</em></p>
<section2topic="Jingle Client Searches for Services on online Roster Entries"anchor="clientcheckownserver">
<p>A Jingle Client MAY NOT be satisfied with only one Relay Service entry found. So it keeps the search on his Roster Items until find the desired amount of Relay Services, or while it does NOT exceed a search depth or ANY other Client implementation policy. The Client SHOULD keep a list of visited Tracker Services in order to avoid searching twice in same Service Entity.</p>
<p>In this example 'juliet@capulet.lit/balcony' returned a Relay Service entry that is restricted to its roster. This Service is usable as the requester has 'juliet@capulet.lit/balcony' on its roster. Although, services with policy 'roster' MUST NOT be listed in Tracker Responses expects in Tracker Responses that comes from the Service Entity itself, in this case 'juliet@capulet.lit/balcony'.</p>
<p><em>In the presented example 'romeo@montague.lit/orchard' knows that 'juliet@capulet.lit/balcony' provides Relay Service, but if another entity requests 'romeo@montague.lit/orchard' its known services, it MUST NOT include 'juliet@capulet.lit/balcony' as it is a roster restricted entry.</em></p>
<p>A Jingle Client with Internet connectivity wheter with direct access to a public IP or not, can potentially provide the Relay Service becaming itself a Jingle Relay Node. The service can intend to provide a public service, or a restricted services based on user preferences, like buddylist, allow/deny lists, domain, etc...</p>
<p><em>After receiving the &CHANNEL; the requester MUST send his stream to 'host' and 'localport' pair and send a &CANDIDATE; containing the 'host' and 'remoteport' values.</em></p>
<p>A Jingle Client can request volative TURN credentials, to be used in cases where connectivity check is a requirement. Like, for example, WebRTC. The concept and mechanism is quite similar to the RFC draft <linkurl='https://tools.ietf.org/html/draft-uberti-behave-turn-rest-00'>REST API For Access To TURN Services'.</link></p>
<p>TURN provides an access control mechanism described in &rfc5389;, where long-term credentials are provided as part of the TURN protocol. Therefore the credentials provided in this Jingle Nodes mechanism are time-limited, but SHOULD be used as long-term credentials, when authentication against a TURN Server.
</p>
<p>
<em>Note: There is no need to run TURN server or support within a Jingle Relay. This mechanism allows decoupled deployment of distributed TURN Servers, without the requirement of database based authentication. </em>
<p>A Relay Channel Service is responsible for providing the actual Relay Services. It will receive Channel Requests, allocate the Relay Channel and return the ready to use details. If a Jingle Client knows the service address of one valid and reliable Relay Service, that is enough for place and receive Jingle Calls and transmit both ways media streams based on UDP.</p>
<p>Relay Channel Services support can be discovered by searching using <linkurl='#trackerservice'>Tracker Services</link>. It can also be discovered by <linkurl='#support'>service discovery described in this document</link>.</p>
<p>Tracker entries MUST contain a 'type' attribute that represents the usage policy according to the table below:</p>
<tablecaption="Types of Service Usage Policy">
<tr>
<th>Type</th>
<th>Definition</th>
</tr>
<tr>
<td>public</td>
<td>Relays Services that are meant and opened for public usage, SHOULD use the type 'public'. Meaning that every user can make use of its services. This type SHOULD be published by Tracker Services.</td>
</tr>
<tr>
<td>roster</td>
<td>Relay Services that only provides Channels for users that are in it own roster, SHOULD use the type 'roster'. Meaning that only presence subscribed buddies can make use of its service. Common usage is XMPP Clients with Relay Services Capabilities. This type SHOULD NOT be published by Tracker Services as if it is roster only, the requester SHOULD have the entity already added to his roster, which also mean that it SHOULD be discoverable on roster level.</td>
<p>The attributes of the &CHANNEL; element are as follows.</p>
<tablecaption="Attributes of Channel Element">
<tr>
<th>Attribute</th>
<th>Definition</th>
<th>Inclusion</th>
</tr>
<tr>
<td>id</td>
<td>A random candidate identifier generated by the Relay Service, which effectively maps to the created Channel; this SHOULD match the XML Nmtoken production <note>See <<linkurl='http://www.w3.org/TR/2000/WD-xml-2e-20000814#NT-Nmtoken'>http://www.w3.org/TR/2000/WD-xml-2e-20000814#NT-Nmtoken</link>></note> so that XML character escaping is not needed for characters such as '&'. In some situations the Jingle session identifier might have security implications. See &rfc4086; regarding requirements for randomness.</td>
<td>REQUIRED on response, NOT RECOMMENDED on requests</td>
<p>The value of the 'host' attribute MUST be one IP address or a DNS resolvable address. That is the address to be used on candidate offering and also the IP to be used when sending out the media traffic.</p>
<p>The value of the 'localport' attribute MUST be a valid IP Port number. This port MUST be used as the media traffic destination port of the channel requester. Session Initiator and responder MUST NOT offer this port.</p>
<p>The rule is simple and unique, the requester of the channel MUST send the media streams to 'localport' and use 'remoteport' in the 'candidate' element to be offered in the Jingle Session.</p>
<p>For transparent compatibility with major RTP Proxy Deployments, an RCTP Port is allocated and defined by default at Localport Attribute Value plus one. (Localport + 1)</p>
<p>The value of the 'remoteport' attribute MUST be a valid IP Port number. This port MUST be used as media traffic destination port of the other party. Channel requester MUST use this port value in the candidate offer in combination with the 'host' attribute. Channel requester MUST NOT send any media stream to this port.</p>
<p>For transparent compatibility with major RTP Proxy Deployments, an RCTP Port is allocated and defined by default at Remoteport Attribute Value plus one. (Localport + 1)</p>
<p>The value of the 'protocol' attribute MUST be a valid protocol value: 'udp' or 'tcp' as also defined in the <linkurl='#schema'>XML Schema</link></p>
<p>The value of the 'maxkbps' attribute MUST be a valid integer value representing the maximum kilobits per seconds the channel supports. This attribute is optional and MAY be used in Relay Channel with bandwidth limitation.</p>
<p>The value of the 'expire' attribute MUST be a valid integer value representing the maximum seconds that the channel can stay without receiving any traffic without being deactivated and closed. This attribute is required and SHOULD be used in all Relay Channels.</p>
<section2topic="TURN Credentials Service Element"anchor="def-turn-credentials">
<p>The attributes of the &TURN; element are as follows.</p>
<tablecaption="Attributes of TURN Elements">
<tr>
<th>Attribute</th>
<th>Definition</th>
<th>Inclusion</th>
</tr>
<tr>
<td>ttl</td>
<td>The duration in seconds for which the provided credentials are valid.</td>
<td>REQUIRED</td>
</tr>
<tr>
<td>uri</td>
<td>The TURN Server URI.</td>
<td>REQUIRED</td>
</tr>
<tr>
<td>username</td>
<td>The username to be used on TURN authentication. THe recommended format is a colon-delimited concatenation of expiration timestamp and the requester bare JID.</td>
<td>REQUIRED</td>
</tr>
<tr>
<td>password</td>
<td>The ppassword to be used on TURN authentication. Is the result of 'base64(hmac(secret_key, username))'. Where 'secret_key' is shared between the TURN server and entity providing the credentials.</td>
<p>The TURN Server URI as described in <linkurl="https://tools.ietf.org/html/draft-petithuguenin-behave-turn-uris-03">I-D.petithuguenin-behave-turn-uris</link></p>
<p>Along with 'username', WebRTC's TURN request uses the 'password' value for its USERNAME and PASSWORD attributes, for the input to the MESSAGE-INTEGRITY hash.</p>
<p>To advertise its support for the Jingle Nodes support, when replying to &xep0030; information requests an entity MUST return URNs for any version of this protocol that the entity supports -- e.g., "http://jabber.org/protocol/jinglenodes" for this version&VNOTE;.</p>
<p>If the entity supports, Jingle Nodes as a Tracker, it MUST reply to &xep0030; with "http://jabber.org/protocol/jinglenodes". If it also provides the Jingle Nodes Relay Services, it MUST reply with the URN "http://jabber.org/protocol/jinglenodes#channel".</p>
<p>For optimization purpose the Client SHOULD check for Jingle Nodes support based on entity presence capabilities &xep0115;, which SHOULD contain the keywork "jn-v0".</p>
<examplecaption="Service discovery information request"><