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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<link href="webrtc.css" rel="stylesheet">
<title>WebRTC 1.0: Real-time Communication Between Browsers</title>
<script class="remove" src=
"https://www.w3.org/Tools/respec/respec-w3c-common" type="text/javascript">
// // keep this comment //
</script>
<script class="remove" src="webrtc.js" type="text/javascript">
// // keep
this comment //
</script>
</head>
<body>
<section id="abstract">
<p>This document defines a set of ECMAScript APIs in WebIDL to allow media
to be sent to and received from another browser or device implementing the
appropriate set of real-time protocols. This specification is being
developed in conjunction with a protocol specification developed by the
IETF RTCWEB group and an API specification to get access to local media
devices developed by the Media Capture Task Force.</p>
</section>
<section id="sotd">
<p>The Editors and active contributors of WebRTC 1.0 intend to publish a
Candidate Recommendation soon. Consequently, this is a Request for Comments
by the WebRTC Working Group to seek wide review of this document.</p>
<p>The API is based on preliminary work done in the WHATWG.</p>
</section>
<section class="informative" id="intro">
<h2>Introduction</h2>
<p>There are a number of facets to video-conferencing in HTML covered by
this specification:</p>
<ul>
<li>Connecting to remote peers using NAT-traversal technologies such as
ICE, STUN, and TURN.</li>
<li>Sending the locally-produced tracks to remote peers and receiving
tracks from remote peers.</li>
<li>Sending arbitrary data directly to remote peers.</li>
</ul>
<p>This document defines the APIs used for these features. This
specification is being developed in conjunction with a protocol
specification developed by the <a href=
"https://datatracker.ietf.org/wg/rtcweb/">IETF RTCWEB group</a> and an API
specification to get access to local media devices [[!GETUSERMEDIA]]
developed by the <a href="https://www.w3.org/wiki/Media_Capture">Media
Capture Task Force</a>. An overview of the system can be found in
[[RTCWEB-OVERVIEW]] and [[RTCWEB-SECURITY]].</p>
</section>
<section id="conformance">
<p>This specification defines conformance criteria that apply to a single
product: the <dfn>user agent</dfn> that implements the interfaces that it
contains.</p>
<p>Conformance requirements phrased as algorithms or specific steps may be
implemented in any manner, so long as the end result is equivalent. (In
particular, the algorithms defined in this specification are intended to be
easy to follow, and not intended to be performant.)</p>
<p>Implementations that use ECMAScript to implement the APIs defined in
this specification MUST implement them in a manner consistent with the
ECMAScript Bindings defined in the Web IDL specification [[!WEBIDL-1]], as
this specification uses that specification and terminology.</p>
</section>
<section>
<h2>Terminology</h2>
<p>The <code><a href=
"http://dev.w3.org/html5/spec/webappapis.html#eventhandler">EventHandler</a></code>
interface, representing a callback used for event handlers, and the
<a href="http://dev.w3.org/html5/spec/webappapis.html#errorevent"><code><dfn>
ErrorEvent</dfn></code></a> interface are defined in [[!HTML5]].</p>
<p>The concepts <dfn><a href=
"http://dev.w3.org/html5/spec/webappapis.html#queue-a-task">queue a
task</a></dfn>, <dfn><a href=
"http://dev.w3.org/html5/spec/webappapis.html#fire-a-simple-event">fire a
simple event</a></dfn> and <dfn><a href=
"http://dev.w3.org/html5/spec/webappapis.html#networking-task-source">networking
task source</a></dfn> are defined in [[!HTML5]].</p>
<p>The terms <dfn>event</dfn>, <dfn><a href=
"http://dev.w3.org/html5/spec/webappapis.html#event-handlers">event
handlers</a></dfn> and <dfn><a href=
"http://dev.w3.org/html5/spec/webappapis.html#event-handler-event-type">event
handler event types</a></dfn> are defined in [[!HTML5]].</p>
<p>The terms <dfn>MediaStream</dfn>, <dfn>MediaStreamTrack</dfn>, and
<dfn>MediaStreamConstraints</dfn> are defined in [[!GETUSERMEDIA]].</p>
<p>The term <dfn>Blob</dfn> is defined in [[!FILEAPI]].</p>
<p>The term <dfn>media description</dfn> is defined in [[!RFC4566]].</p>
</section>
<section>
<h2>Peer-to-peer connections</h2>
<section>
<h3>Introduction</h3>
<p>An <code><a>RTCPeerConnection</a></code> instance allows to establish
peer to peer communications. Communications are coordinated via a
signaling channel which is provided by unspecified means, but generally
by a script in the page via the server, e.g. using
<code>XMLHttpRequest</code> [[XMLHttpRequest]] or Web Sockets
[[WEBSOCKETS-API]].</p>
</section>
<section>
<h3>Configuration</h3>
<section>
<h4>RTCConfiguration Dictionary</h4>
<p>The <code>RTCConfiguration</code> defines a set of parameters to
configure how the peer to peer communication established via
<code><a>RTCPeerConnection</a></code> is established or
re-established.</p>
<div>
<pre class="idl">dictionary RTCConfiguration {
sequence<RTCIceServer> iceServers;
RTCIceTransportPolicy iceTransportPolicy = "all";
RTCBundlePolicy bundlePolicy = "balanced";
RTCRtcpMuxPolicy rtcpMuxPolicy = "require";
DOMString peerIdentity;
sequence<RTCCertificate> certificates;
unsigned short iceCandidatePoolSize = 0;
};</pre>
<section>
<h2>Dictionary <a class="idlType">RTCConfiguration</a> Members</h2>
<dl data-link-for="RTCConfiguration" data-dfn-for=
"RTCConfiguration" class="dictionary-members">
<dt><dfn><code>iceServers</code></dfn> of type <span class=
"idlMemberType">sequence<<a>RTCIceServer</a>></span></dt>
<dd>
<p>An array of objects describing servers available to be used
by ICE, such as STUN and TURN servers.</p>
</dd>
<dt><dfn><code>iceTransportPolicy</code></dfn> of type
<span class="idlMemberType"><a>RTCIceTransportPolicy</a></span>,
defaulting to <code>"all"</code></dt>
<dd>
<p>Indicates which candidates the <a>ICE Agent</a> is allowed
to use.</p>
</dd>
<dt><dfn><code>bundlePolicy</code></dfn> of type <span class=
"idlMemberType"><a>RTCBundlePolicy</a></span>, defaulting to
<code>"balanced"</code></dt>
<dd>
<p>Indicates which <a>media-bundling policy</a> to use when
gathering ICE candidates.</p>
</dd>
<dt><dfn><code>rtcpMuxPolicy</code></dfn> of type <span class=
"idlMemberType"><a>RTCRtcpMuxPolicy</a></span>, defaulting to
<code>"require"</code></dt>
<dd>
<p>Indicates which <a>rtcp-mux policy</a> to use when gathering
ICE candidates.</p>
</dd>
<dt><dfn><code>peerIdentity</code></dfn> of type <span class=
"idlMemberType"><a>DOMString</a></span></dt>
<dd>
<p>Sets the <a>target peer identity</a> for the
<a>RTCPeerConnection</a>. The <a>RTCPeerConnection</a> will not
establish a connection to a remote peer unless it can be
successfully authenticated with the provided name.</p>
</dd>
<dt><dfn><code>certificates</code></dfn> of type <span class=
"idlMemberType">sequence<<a>RTCCertificate</a>></span></dt>
<dd>
<p>A set of certificates that the
<a><code>RTCPeerConnection</code></a> uses to authenticate.</p>
<p>Valid values for this parameter are created through calls to
the <a data-for=
"RTCPeerConnection"><code>generateCertificate</code></a>
function.</p>
<p>Although any given DTLS connection will use only one
certificate, this attribute allows the caller to provide
multiple certificates that support different algorithms. The
final certificate will be selected based on the DTLS handshake,
which establishes which certificates are allowed. The
<code>RTCPeerConnection</code> implementation selects which of
the certificates is used for a given connection; how
certificates are selected is outside the scope of this
specification.</p>
<p>If this value is absent, then a default set of certificates
is generated for each <a><code>RTCPeerConnection</code></a>
instance.</p>
<p>This option allows applications to establish key continuity.
An <code>RTCCertificate</code> can be persisted in
[[INDEXEDDB]] and reused. Persistence and reuse also avoids the
cost of key generation.</p>
<p>The value for this configuration option cannot change after
its value is initially selected.</p>
</dd>
<dt><dfn><code>iceCandidatePoolSize</code></dfn> of type
<span class="idlMemberType"><a>unsigned short</a></span>,
defaulting to <code>0</code></dt>
<dd>
<p>Size of the prefetched ICE pool as defined in
<span data-jsep=
"ice-candidate-pool constructor">[[!JSEP]]</span>.</p>
</dd>
</dl>
</section>
</div>
</section>
<section>
<h4>RTCIceCredentialType Enum</h4>
<div>
<pre class="idl">enum RTCIceCredentialType {
"password",
"token"
};</pre>
<table data-link-for="RTCIceCredentialType" data-dfn-for=
"RTCIceCredentialType" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description</th>
</tr>
<tr>
<td><dfn><code>password</code></dfn></td>
<td>The credential is a long-term authentication password, as
described in [[!RFC5389]], Section 10.2.</td>
</tr>
<tr>
<td><dfn><code>token</code></dfn></td>
<td>The credential is an access token, as described in
[[!TRAM-TURN-THIRD-PARTY-AUTHZ]], Section 6.2.</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4>RTCIceServer Dictionary</h4>
<p>The <code>RTCIceServer</code> dictionary is used to describe the
STUN and TURN servers that can be used by the <a>ICE Agent</a> to
establish a connection with a peer.</p>
<div>
<pre class="idl">dictionary RTCIceServer {
required (DOMString or sequence<DOMString>) urls;
DOMString username;
DOMString credential;
RTCIceCredentialType credentialType = "password";
};</pre>
<section>
<h2>Dictionary <a class="idlType">RTCIceServer</a> Members</h2>
<dl data-link-for="RTCIceServer" data-dfn-for="RTCIceServer" class=
"dictionary-members">
<dt><dfn><code>urls</code></dfn> of type <span class=
"idlMemberType"><a>(DOMString or
sequence<DOMString>)</a></span>, required</dt>
<dd>
<p>STUN or TURN URI(s) as defined in [[!RFC7064]] and
[[!RFC7065]] or other URI types.</p>
</dd>
<dt><dfn><code>username</code></dfn> of type <span class=
"idlMemberType"><a>DOMString</a></span></dt>
<dd>
<p>If this <code><a>RTCIceServer</a></code> object represents a
TURN server, then this attribute specifies the username to use
with that TURN server.</p>
</dd>
<dt><dfn><code>credential</code></dfn> of type <span class=
"idlMemberType"><a>DOMString</a></span></dt>
<dd>
<p>If this <code><a>RTCIceServer</a></code> object represents a
TURN server, then this attribute specifies the credential to
use with that TURN server.</p>
</dd>
<dt><dfn><code>credentialType</code></dfn> of type <span class=
"idlMemberType"><a>RTCIceCredentialType</a></span>, defaulting to
<code>"password"</code></dt>
<dd>
<p>If this <code><a>RTCIceServer</a></code> object represents a
TURN server, then this attribute specifies how
<var>credential</var> should be used when that TURN server
requests authorization.</p>
</dd>
</dl>
</section>
</div>
<p>An example array of RTCIceServer objects is:</p>
<pre class="example highlight"><code>[
{ "urls": "stun:stun1.example.net" },
{ "urls": ["turns:turn.example.org", "turn:turn.example.net"],
"username": "user",
"credential": "myPassword",
"credentialType": "password" }
]</code></pre>
</section>
<section>
<h4>RTCIceTransportPolicy Enum</h4>
<p>As noted in <span data-jsep="constructor">[[!JSEP]]</span>, if the
<a data-link-for='RTCConfiguration'>iceTransportPolicy</a> member of
the <code>RTCConfiguration</code> is specified, it defines the
<span data-jsep="ice-candidate-policy">ICE candidate policy
[[!JSEP]]</span> the browser uses to surface the permitted candidates
to the application; only these candidates will be used for connectivity
checks.</p>
<div>
<pre class="idl">enum RTCIceTransportPolicy {
"relay",
"all"
};</pre>
<table data-link-for="RTCIceTransportPolicy" data-dfn-for=
"RTCIceTransportPolicy" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description</th>
</tr>
<tr>
<td><dfn><code>relay</code></dfn></td>
<td>
The <a>ICE Agent</a> MUST only use media relay candidates
such as candidates passing through a TURN server. This can be
used to reduce leakage of IP addresses in certain use cases.
</td>
</tr>
<tr>
<td><dfn><code>all</code></dfn></td>
<td>
The <a>ICE Agent</a> MAY use any type of candidates when this
value is specified. This will not include addresses that have
been filtered by the browser.
</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4>RTCBundlePolicy Enum</h4>
<p>As described in <span data-jsep="constructor">[[!JSEP]]</span>,
bundle policy affects which media tracks are negotiated if the remote
endpoint is not bundle-aware, and what ICE candidates are gathered. If
the remote endpoint is bundle-aware, all media tracks and data channels
are bundled onto the same transport.</p>
<div>
<pre id="target-bundle-policy" class="idl">enum RTCBundlePolicy {
"balanced",
"max-compat",
"max-bundle"
};</pre>
<table data-link-for="RTCBundlePolicy" data-dfn-for="RTCBundlePolicy"
class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description (non-normative)</th>
</tr>
<tr>
<td><dfn><code>balanced</code></dfn></td>
<td>Gather ICE candidates for each media type in use (audio,
video, and data). If the remote endpoint is not bundle-aware,
negotiate only one audio and video track on separate
transports.</td>
</tr>
<tr>
<td><dfn><code>max-compat</code></dfn></td>
<td>Gather ICE candidates for each track. If the remote
endpoint is not bundle-aware, negotiate all media tracks on
separate transports.</td>
</tr>
<tr>
<td><dfn><code>max-bundle</code></dfn></td>
<td>Gather ICE candidates for only one track. If the remote
endpoint is not bundle-aware, negotiate only one media
track.</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4>RTCRtcpMuxPolicy Enum</h4>
<p>As described in <span data-jsep="constructor">[[!JSEP]]</span>, the
RtcpMuxPolicy affects what ICE candidates are gathered to support
non-multiplexed RTCP.</p>
<div>
<pre id="target-rtcp-mux-policy" class="idl">enum RTCRtcpMuxPolicy {
"negotiate",
"require"
};</pre>
<table data-link-for="RTCRtcpMuxPolicy" data-dfn-for=
"RTCRtcpMuxPolicy" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description (non-normative)</th>
</tr>
<tr>
<td><dfn><code>negotiate</code></dfn></td>
<td>Gather ICE candidates for both RTP and RTCP candidates. If
the remote-endpoint is capable of multiplexing RTCP, multiplex
RTCP on the RTP candidates. If it is not, use both the RTP and
RTCP candidates separately.</td>
</tr>
<tr>
<td><dfn><code>require</code></dfn></td>
<td>Gather ICE candidates only for RTP and multiplex RTCP on
the RTP candidates. If the remote endpoint is not capable of
rtcp-mux, session negotiation will fail.</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4>Offer/Answer Options</h4>
<p>These dictionaries describe the options that can be used to control
the offer/answer creation process.</p>
<div>
<pre class="idl">dictionary RTCOfferAnswerOptions {
boolean voiceActivityDetection = true;
};</pre>
<section>
<h2>Dictionary <a class="idlType">RTCOfferAnswerOptions</a>
Members</h2>
<dl data-link-for="RTCOfferAnswerOptions" data-dfn-for=
"RTCOfferAnswerOptions" class="dictionary-members">
<dt><dfn><code>voiceActivityDetection</code></dfn> of type
<span class="idlMemberType"><a>boolean</a></span>, defaulting to
<code>true</code></dt>
<dd>
<p>Many codecs and systems are capable of detecting "silence"
and changing their behavior in this case by doing things such
as not transmitting any media. In many cases, such as when
dealing with emergency calling or sounds other than spoken
voice, it is desirable to be able to turn off this behavior.
This option allows the application to provide information about
whether it wishes this type of processing enabled or
disabled.</p>
</dd>
</dl>
</section>
</div>
<div>
<pre class="idl">dictionary RTCOfferOptions : RTCOfferAnswerOptions {
boolean iceRestart = false;
};</pre>
<section>
<h2>Dictionary <a class="idlType">RTCOfferOptions</a> Members</h2>
<dl data-link-for="RTCOfferOptions" data-dfn-for="RTCOfferOptions"
class="dictionary-members">
<dt><dfn><code>iceRestart</code></dfn> of type <span class=
"idlMemberType"><a>boolean</a></span>, defaulting to
<code>false</code></dt>
<dd>
<p>When the value of this dictionary member is true, the
generated description will have ICE credentials that are
different from the current credentials (as visible in the
<code><a data-link-for=
"RTCPeerConnection">localDescription</a></code> attribute's
SDP). Applying the generated description will restart ICE.</p>
<p>When the value of this dictionary member is false, and the
<code><a data-link-for=
"RTCPeerConnection">localDescription</a></code> attribute has
valid ICE credentials, the generated description will have the
same ICE credentials as the current value from the
<code><a data-link-for=
"RTCPeerConnection">localDescription</a></code> attribute.</p>
</dd>
</dl>
</section>
</div>
<div>
<pre class="idl">
dictionary RTCAnswerOptions : RTCOfferAnswerOptions {
};</pre>
</div>
</section>
</section>
<section>
<h3>RTCPeerConnection Interface</h3>
<p>The [[!JSEP]] specification, as a whole, describes the details of how
the <code><a>RTCPeerConnection</a></code> operates. References to
specific subsections of [[!JSEP]] are provided as appropriate.</p>
<section>
<h4>Operation</h4>
<p>Calling <code>new <a>RTCPeerConnection</a>(<var>configuration</var>
)</code> creates an <code><a>RTCPeerConnection</a></code> object.</p>
<p>The <var>configuration</var> has the information to find and access
the servers used by ICE. There may be multiple servers of each type and
any TURN server also acts as a STUN server.</p>
<p>An <code><a>RTCPeerConnection</a></code> object has a <dfn>signaling
state</dfn>, a <dfn>connection state</dfn>, an <dfn>ICE gathering
state</dfn>, and an <dfn>ICE connection state</dfn>. These are
initialized when the object is created.</p>
<p data-link-for="RTCPeerConnection">The ICE protocol implementation of
an <code><a>RTCPeerConnection</a></code> is represented by an <dfn>ICE
agent</dfn> [[!ICE]]. Certain <code><a>RTCPeerConnection</a></code>
methods involve interactions with the <a>ICE Agent</a>, namely
<code><a>addIceCandidate</a></code>, <code><a>setConfiguration</a></code>,
<code><a>setLocalDescription</a></code>,
<code><a>setRemoteDescription</a></code> and <code><a>close</a></code>.
These interactions are described in the relevant sections in this
document and in [[!JSEP]]. The <a>ICE Agent</a> also provides
indications to the User Agent when the state of its internal
representation of an <code><a>RTCIceTransport</a></code> changes, as
described in <a href= "#rtcicetransport"></a>.</p>
<p>When the <dfn id=
"dom-peerconnection"><code>RTCPeerConnection()</code></dfn> constructor
is invoked, the user agent MUST run the following steps:</p>
<ol>
<li>
<p>Let <var>connection</var> be a newly created
<code><a>RTCPeerConnection</a></code> object.</p>
</li>
<li>
<p>Initialize <var>connection</var>'s <a>ICE Agent</a>.</p>
</li>
<li>
<p><a>Set the configuration</a> specified by the constructor's
first argument.</p>
</li>
<li>
<p>Let <var>connection</var> have an [[<dfn>isClosed</dfn>]]
internal slot, initialized to <code>false</code>.</p>
</li>
<li>
<p>Let <var>connection</var> have a [[<dfn>needNegotiation</dfn>]]
internal slot, initialized to <code>false</code>.</p></li>
<li>
<p>Let <var>connection</var> have an [[<dfn>operations</dfn>]]
internal slot, representing an <a>operations queue</a>, initialized
to an empty list.</p>
</li>
<li>
<p>Set <var>connection</var>'s <a>signaling state</a> to
<code>stable</code>.</p>
</li>
<li>
<p>Set <var>connection</var>'s <a>ICE connection state</a> to
<code>new</code>.</p>
</li>
<li>
<p>Set <var>connection</var>'s <a>ICE gathering state</a> to
<code>new</code>.</p>
</li>
<li>
<p>Set <var>connection</var>'s <a>connection state</a> to
<code>new</code>.</p>
</li>
<li>
<p>Set <var>connection</var>'s <code><a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>,
<code><a data-for=
"RTCPeerConnection">currentLocalDescription</a></code>,
<code><a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code> and
<code><a data-for=
"RTCPeerConnection">currentRemoteDescription</a></code> to
null.</p>
</li>
<li>
<p>If the <code>certificates</code> value in the
<code>RTCConfiguration</code> structure is non-empty, check that
the <code>expires</code> on each value is in the future. If a
certificate has expired, throw an <code>InvalidAccessError</code>
exception and abort these steps; otherwise, store the certificates.
If no <code>certificates</code> value was specified, one or more
new <code>RTCCertificate</code> instances are generated for use
with this <code>RTCPeerConnection</code> instance.</p>
</li>
<li>
<p>Store the configuration, including the certificates, in a
[[<dfn>configuration</dfn>]] internal slot.</p>
</li>
<li>
<p>Return <var>connection</var>.</p>
</li>
</ol>
<p>An <code><a>RTCPeerConnection</a></code> object has an
<dfn>operations queue</dfn>, [[<a>operations</a>]], which ensures that
only one asynchronous operation in the queue is executed concurrently.
If subsequent calls are made while the returned promise of a previous
call is still not settled, they are added to the queue and executed
when all the previous calls have finished executing and their promises
have settled.</p>
<p>To <dfn id="enqueue-an-operation">enqueue an operation</dfn>, run
the following steps:</p>
<ol>
<li>
<p>Let <var>connection</var> be the current
<code><a>RTCPeerConnection</a></code> object.</p>
</li>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, return a promise rejected with an
<code>InvalidStateError</code>.</p>
</li>
<li>
<p>Let <var>operation</var> be the operation to be enqueued.</p>
</li>
<li>
<p>Let <var>p</var> be a new promise.</p>
</li>
<li>
<p>Append <var>operation</var> to [[<a>operations</a>]].</p>
</li>
<li>
<p>If the length of [[<a>operations</a>]] is exactly 1, execute
<var>operation</var>.</p>
</li>
<li>
<p>Upon fulfillment or rejection of the promise returned by the
<var>operation</var>, run the following steps:</p>
<ol>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, abort these steps.</p>
</li>
<li>
<p>If the promise returned by <var>operation</var> was
fulfilled with a value, fulfill <var>p</var> with that
value.</p>
</li>
<li>
<p>If the promise returned by <var>operation</var> was rejected
with a value, reject <var>p</var> with that value.</p>
</li>
<li>
<p>Upon fulfillment or rejection of <var>p</var>, execute the
following steps:</p>
<ol>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, abort these steps.</p>
</li>
<li>
<p>Remove the first element of [[<a>operations</a>]].</p>
</li>
<li>
<p>If [[<a>operations</a>]] is non-empty, execute the
operation represented by the first element of
[[<a>operations</a>]].</p>
</li>
</ol>
</li>
</ol>
</li>
<li>
<p>Return <var>p</var>.</p>
</li>
</ol>
<p>An <code><a>RTCPeerConnection</a></code> object has an aggregated
<a>connection state</a>. Whenever the state of an
<code><a>RTCDtlsTransport</a></code> or
<code><a>RTCIceTransport</a></code> changes or when the
[[<a>isClosed</a>]] slot turns <code>true</code>, the User Agent MUST
<dfn>update the connection state</dfn> by queueing a task that runs the
following steps:</p>
<ol>
<li>
<p>Let <var>connection</var> be this
<code><a>RTCPeerConnection</a></code> object.</p>
</li>
<li>
<p>Let <var>newState</var> be the value of deriving a new state
value as described by the
<a><code>RTCPeerConnectionState</code></a> enum.</p>
</li>
<li>
<p>If <var>connection</var>'s <a>connection state</a> is equal to
<var>newState</var>, abort these steps.</p>
</li>
<li>
<p>Let <var>connection</var>'s <a>connection state</a> be
<var>newState</var>.</p>
</li>
<li>
<p>Fire a simple event named
<code><a>connectionstatechange</a></code> at
<var>connection</var>.</p>
</li>
</ol>
<p>To <dfn id="update-ice-gathering-state">update the <a>ICE gathering
state</a></dfn> of an <code><a>RTCPeerConnection</a></code> instance
<var>connection</var>, the User Agent MUST queue a task that runs the
following steps:</p>
<ol>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, abort these steps.</p>
</li>
<li>
<p>Let <var>newState</var> be the value of deriving a new state
value as described by the <a><code>RTCIceGatheringState</code></a>
enum.</p>
</li>
<li>
<p>If <var>connection</var>'s <a>ICE gathering state</a> is equal to
<var>newState</var>, abort these steps.</p>
</li>
<li>
<p>Set <var>connection</var>'s <a>ice gathering state</a> to
<var>newState</var>.</p>
</li>
<li>
<p>Fire a simple event named
<code><a>icegatheringstatechange</a></code> at
<var>connection</var>.</p>
</li>
<li>
<p>If <var>newState</var> is <code>completed</code>, fire an event
named <code><a>icecandidate</a></code> with <code>null</code> at
<var>connection</var>.</p>
</li>
</ol>
<p>To <dfn id="update-ice-connection-state">update the <a>ICE
connection state</a></dfn> of an <code><a>RTCPeerConnection</a></code>
instance <var>connection</var>, the User Agent MUST queue a task that
runs the following steps:</p>
<ol>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, abort these steps.</p>
</li>
<li>
<p>Let <var>newState</var> be the value of deriving a new state
value as described by the <a><code>RTCIceConnectionState</code></a>
enum.</p>
</li>
<li>
<p>If <var>connection</var>'s <a>ICE connection state</a> is equal
to <var>newState</var>, abort these steps.</p>
</li>
<li>
<p>Set <var>connection</var>'s <a>ice connection state</a> to
<var>newState</var>.</p>
</li>
<li>
<p>Fire a simple event named
<code><a>iceconnectionstatechange</a></code> at
<var>connection</var>.</p>
</li>
</ol>
<p>To <dfn id="set-description" data-lt=
"set the RTCSessionDescription">set an RTCSessionDescription</dfn>
<var>description</var> on an <code><a>RTCPeerConnection</a></code>
object <var>connection</var>, <a href=
"#enqueue-an-operation">enqueue</a> the following steps:</p>
<ol>
<li>
<p>Let <var>p</var> be a new promise.</p>
</li>
<li>
<p>In parallel, start the process to apply <var>description</var>
as described in <span data-jsep=
"processing-a-local-desc processing-a-remote-desc">[[!JSEP]]</span>.</p>
<ol>
<li>
<p>If the process to apply <var>description</var> fails for any
reason, then user agent MUST queue a task runs the following
steps:</p>
<ol>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, then abort these steps.</p>
</li>
<li>
<p>If elements of the SDP were modified, then reject
<var>p</var> with an <code>InvalidModificationError</code>
and abort these steps.</p>
</li>
<li>
<p>If the <var>description</var>'s <code><a data-for=
"RTCSessionDescription">type</a></code> is invalid for the
current <a>signaling state</a> of <var>connection</var>,
then reject <var>p</var> with a
<code>InvalidStateError</code> and abort these steps.</p>
</li>
<li>
<p>If the content of <var>description</var> is not
valid SDP syntax, then reject <var>p</var> with an
<code>RTCError</code> (with <code>errorDetail</code>
set to "sdpSyntaxError" and the sdpLineNumber
attribute set to the line number in the SDP where
the syntax error was detected) and abort these steps.</p>
</li>
<li>
<p>If the content of <var>description</var> is invalid,
then reject <var>p</var> with an
<code>InvalidAccessError</code> and abort these steps.</p>
</li>
<li>
<p>For all other errors, for example if
<var>description</var> cannot be applied at the media
layer, reject <var>p</var> with
<code>OperationError</code>.</p>
</li>
</ol>
</li>
<li>
<p>If <var>description</var> is applied successfully, the user
agent MUST queue a task that runs the following steps:</p>
<ol>
<li>
<p>If <var>connection</var>'s [[<a>isClosed</a>]] slot is
<code>true</code>, then abort these steps.</p>
</li>
<li>
<p>If <var>description</var> is set as a local description,
then run one of the following steps:</p>
<ul>
<!-- A) transition stable to haveLocalOffer -->
<li>
<p>If <var>description</var> is of type "offer", set
<code><var>connection</var>.<a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>
to <var>description</var> and <a>signaling state</a> to
<code>have-local-offer</code>.</p>
</li>
<!-- C) transition haveRemoteOffer or haveLocalProvAnswer to
stable -->
<li>
<p>If <var>description</var> is of type "answer", then
this completes an offer answer negotiation. Set
<var>connection</var>'s <code><a data-for=
"RTCPeerConnection">currentLocalDescription</a></code>
to <var>description</var> and <code><a data-for=
"RTCPeerConnection">currentRemoteDescription</a></code>
to the value of <code><a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code>.
Set both <code><a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code>
and <code><a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>
to null. Finally set <var>connection</var>'s
<a>signaling state</a> to <code>stable</code></p>
</li>
<!-- B) transition rollback to haveLocalOffer to stable -->
<li>
<p>If <var>description</var> is of type "rollback",
then this is a rollback. Set
<code><var>connection</var>.<a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>
to null and <a>signaling state</a> to
<code>stable</code>.</p>
</li>
<!-- G) transition haveRemoteOffer to haveLocalProvAnswer -->
<li>
<p>If <var>description</var> is of type "pranswer",
then set <code><var>connection</var>.<a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>
to <var>description</var> and <a>signaling state</a> to
<code>have-local-pranswer</code>.</p>
</li>
</ul>
</li>
<li>
<p>Otherwise, if <var>description</var> is set as a remote
description, then run one of the following steps:</p>
<ul>
<!-- D) transition stable to haveRemoteOffer -->
<li>
<p>If <var>description</var> is of type "offer", set
<code><var>connection</var>.<a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code>
attribute to <var>description</var> and <a>signaling
state</a> to <code>have-remote-offer</code>.</p>
</li>
<!-- F) transition haveRemoteOffer or haveLocalProvAnswer to
stable -->
<li>
<p>If <var>description</var> is of type "answer", then
this completes an offer answer negotiation. Set
<var>connection</var>'s <code><a data-for=
"RTCPeerConnection">currentRemoteDescription</a></code>
to <var>description</var> and <code><a data-for=
"RTCPeerConnection">currentLocalDescription</a></code>
to the value of <code><a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>.
Set both <code><a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code>
and <code><a data-for=
"RTCPeerConnection">pendingLocalDescription</a></code>
to null. Finally set <var>connection</var>'s
<a>signaling state</a> to <code>stable</code></p>
</li>
<!-- E) transition rollback to haveRemoteOffer to stable -->
<li>
<p>If <var>description</var> is of type "rollback",
then this is a rollback. Set
<code><var>connection</var>.<a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code>
to null and <a>signaling state</a> to
<code>stable</code>.</p>
</li>
<!-- H) transition haveRemoteOffer to haveLocalProvAnswer -->
<li>
<p>If <var>description</var> is of type "pranswer",
then set <code><var>connection</var>.<a data-for=
"RTCPeerConnection">pendingRemoteDescription</a></code>
to <var>description</var> and <a>signaling state</a> to
<code>have-remote-pranswer</code>.</p>
</li>
</ul>
</li>
<li>
<p>If <var>connection</var>'s <a>signaling state</a>
changed above, fire a simple event named
<code><a>signalingstatechange</a></code> at
<var>connection</var>.</p>
</li>
<li>
<p>If <var>description</var> is set as a remote description
with new media descriptions <span data-jsep=
"media-level-parse">[[!JSEP]]</span>, the User Agent MUST
<a>dispatch a receiver</a> for all new media
descriptions.</p>
</li>
<li>
<p>If <var>description</var> is of type "rollback", then run
the following steps:</p>
<ol>
<li>
<p>If the <code><a data-for=
"RTCRtpTransceiver">mid</a></code> value of an
<code><a>RTCRtpTransceiver</a></code> was set to a
non-null value by the
<code><a>RTCSessionDescription</a></code> that is being
rolled back, set the <code><a data-for=
"RTCRtpTransceiver">mid</a></code> value of that
transceiver to null, as described by <span data-jsep=
"rollback">[[!JSEP]]</span>.</p>
</li>
<li>
<p>If an <code><a>RTCRtpTransceiver</a></code> was
created by applying the
<code><a>RTCSessionDescription</a></code> that is
being rolled back, and a track has not been attached to
it via <code>addTrack</code>, remove that
transceiver from <var>connection</var>'s <a
href="#transceivers-set">set of transceivers</a>, as
described by <span data-jsep=
"rollback">[[!JSEP]]</span>.</p>
</li>
</ol>
</li>
<li>
<p>If <var>connection</var>'s <a>signaling state</a> is now
<code>stable</code>, <a>update the negotiation-needed
flag</a>. If <var>connection</var>'s
[[<a>needNegotiation</a>]] slot was <code>true</code> both
before and after this update, queue a task to check
<var>connection</var>'s [[<a>needNegotiation</a>]] slot and,
if still <code>true</code>, fire a simple event named
<a>negotiationneeded</a> at <var>connection</var>.</p>
</li>
<li>
<p>Resolve <var>p</var> with <var>undefined</var>.</p>
</li>
</ol>
</li>
</ol>
</li>
<li>
<p>Return <var>p</var>.</p>
</li>
</ol>
<p>The task source for the tasks listed in this section is the
<a>networking task source</a>.</p>
</section>
<section>
<h3>Interface Definition</h3>
<p>The <code><a>RTCPeerConnection</a></code> interface presented in
this section is extended by several partial interfaces throughout this
specification. Notably, the <a>RTP Media API</a> section, which adds
the APIs to send and receive <code><a>MediaStreamTrack</a></code>
objects.</p>
<div>
<pre class="idl">
[ Constructor (optional RTCConfiguration configuration)]
interface RTCPeerConnection : EventTarget {
Promise<RTCSessionDescriptionInit> createOffer (optional RTCOfferOptions options);
Promise<RTCSessionDescriptionInit> createAnswer (optional RTCAnswerOptions options);
Promise<void> setLocalDescription (RTCSessionDescriptionInit description);
readonly attribute RTCSessionDescription? localDescription;
readonly attribute RTCSessionDescription? currentLocalDescription;
readonly attribute RTCSessionDescription? pendingLocalDescription;
Promise<void> setRemoteDescription (RTCSessionDescriptionInit description);
readonly attribute RTCSessionDescription? remoteDescription;
readonly attribute RTCSessionDescription? currentRemoteDescription;
readonly attribute RTCSessionDescription? pendingRemoteDescription;
Promise<void> addIceCandidate ((RTCIceCandidateInit or RTCIceCandidate) candidate);
readonly attribute RTCSignalingState signalingState;
readonly attribute RTCIceGatheringState iceGatheringState;
readonly attribute RTCIceConnectionState iceConnectionState;
readonly attribute RTCPeerConnectionState connectionState;
readonly attribute boolean? canTrickleIceCandidates;
static readonly attribute FrozenArray<RTCIceServer> defaultIceServers;
RTCConfiguration getConfiguration ();
void setConfiguration (RTCConfiguration configuration);
void close ();
attribute EventHandler onnegotiationneeded;
attribute EventHandler onicecandidate;
attribute EventHandler onicecandidateerror;
attribute EventHandler onsignalingstatechange;
attribute EventHandler oniceconnectionstatechange;
attribute EventHandler onicegatheringstatechange;
attribute EventHandler onconnectionstatechange;
attribute EventHandler onfingerprintfailure;
};</pre>
<section>
<h2>Constructors</h2>
<dl data-link-for="RTCPeerConnection" data-dfn-for=
"RTCPeerConnection" class="constructors">
<dt><dfn><code>RTCPeerConnection</code></dfn></dt>
<dd>