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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="respec-w3c-common.js" 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 API is based on preliminary work done in the WHATWG.</p>
<p>While the specification is feature complete and is expected to be stable, there are also a number of <a href="https://github.com/w3c/webrtc-pc/issues?utf8=%E2%9C%93&q=is%3Aopen%20is%3Aissue%20-label%3AEditorial%20">known substantive issues</a> on the specification that will be addressed during the Candidate Recommendation period based on implementation experience feedback.</p>
<p>It might also evolve based on feedback gathered as its <a href="https://github.com/w3c/web-platform-tests/tree/master/webrtc">associated test suite</a> evolves. This test suite will be used to build an <a href="https://wpt.fyi/webrtc">implementation report</a> of the API.</p>
<p>To go into Proposed Recommendation status, the group expects to demonstrate implementation of each feature in at least two deployed browsers, and at least one implementation of each optional feature. Mandatory feature with only one implementation may be marked as optional in a revised Candidate Recommendation where applicable.</p>
<p>The following features are marked as risk:</p>
<ul>
<li>The value <a href="#dom-rtcrtcpmuxpolicy-negotiate"><code>negotiate</code></a> of RTCRtcpMuxPolicy</li>
</ul>
</section>
<section class="informative" id="intro">
<h2>Introduction</h2>
<p>There are a number of facets to peer-to-peer communications and
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 data-cite=
"!HTML51/webappapis.html#event-handler">EventHandler</a></code>
interface, representing a callback used for event handlers, and the
<code><dfn data-cite="!HTML51/webappapis.html#errorevent-errorevent">
ErrorEvent</dfn></code> interface are defined in [[!HTML51]].</p>
<p>The concepts <dfn data-cite="!HTML51/webappapis.html#queuing">queue a
task</dfn>, <dfn data-cite="!HTML51/infrastructure.html#fire">fire a
simple event</dfn> and <dfn data-cite="!HTML51/webappapis.html#networking-task-source">networking
task source</dfn> are defined in [[!HTML51]].</p>
<p>The terms <dfn>event</dfn>, <dfn data-cite="!HTML51/webappapis.html#events-event-handlers">event
handlers</dfn> and <dfn data-cite="!HTML51/webappapis.html#event-handler-event-type">event
handler event types</dfn> are defined in [[!HTML51]].</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>
<p>The term <dfn>media transport</dfn> is defined in [[!RFC7656]].</p>
<p>The term <dfn>generation</dfn> is defined in [[!TRICKLE-ICE]] Section 2.</p>
<p>The term <dfn data-cite="!WEBRTC-STATS#dom-rtcstatstype">RTCStatsType</dfn> is defined in [[!WEBRTC-STATS]].
<p>When referring to exceptions, the terms <dfn
data-cite="!WEBIDL-1#dfn-throw">throw</dfn> and
<dfn data-dfn-for="exception" data-cite=
"!WEBIDL-1#dfn-create-exception">create</dfn> are
defined in [[!WEBIDL-1]].</p>
<p>The terms <dfn data-lt="fulfill|fulfillment">fulfilled</dfn>, <dfn
data-lt="reject|rejection|rejecting">rejected</dfn>, <dfn data-lt=
"resolve|resolves">resolved</dfn>, <dfn>pending</dfn> and
<dfn>settled</dfn> used in the context of Promises are defined in
[[!ECMASCRIPT-6.0]].</p>
</section>
<section>
<h2>Peer-to-peer connections</h2>
<section>
<h3>Introduction</h3>
<p>An <code><a>RTCPeerConnection</a></code> instance allows an
application to establish peer-to-peer communications with another
<code><a>RTCPeerConnection</a></code> instance in another browser, or to
another endpoint implementing the required protocols. Communications are coordinated by the
exchange of control messages (called a signaling protocol) over 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><dfn>RTCConfiguration</dfn> 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;
[EnforceRange]
octet 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>octet</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><dfn>RTCIceCredentialType</dfn> Enum</h4>
<div>
<pre class="idl">enum RTCIceCredentialType {
"password",
"oauth"
};</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 username and
password, as described in [[!RFC5389]], Section 10.2.
</td>
</tr>
<tr>
<td><dfn><code>oauth</code></dfn></td>
<td><p>An OAuth 2.0 based authentication method, as described in
[[!RFC7635]]. It uses the OAuth 2.0 Implicit Grant type, with
PoP (Proof-of-Possession) Token type, as described in
[[!RFC6749]] and [[!OAUTH-POP-KEY-DISTRIBUTION]].
</p>
<p>The <dfn>OAuth Client</dfn> and the <dfn>Auhorization
Server</dfn> roles are defined in [[!RFC6749]] Section 1.1.
</p>
<p>
If [[!RFC7635]] is used in the WebRTC context then the <a>OAuth
Client</a> is responsible for refreshing the credential
information, and updating the <a>ICE Agent</a> with fresh new
credentials before the <code>accessToken</code> expires. The
<a>OAuth Client</a> can use the <a
href="#interface-definition"><code>RTCPeerConnection</code></a>
<a data-lt="setConfiguration"
href="#dom-rtcpeerconnection-setconfiguration"><code>
setConfiguration</code></a> method to periodically refresh the
TURN credentials. </p>
<p>For OAuth Authentication, the <a>ICE Agent</a> requires three
pieces of credential information. The credential is composed of
a <code>kid</code>, which the <a>RTCIceServer</a>
<code>username</code> member is used for, and
<code>macKey</code> and <code> accessToken</code>, which are
placed in the <a>RTCOAuthCredential</a> dictionary. All of this
information can be extracted from the OAuth response parameters,
which are received from the <dfn>Authorization Server</dfn>. The
relevant OAuth response parameters are the "kid", the "key", and
the "access_token". These can be used to extract all the
necessary credential infromation (the <code>kid</code>,
<code>macKey</code>, and <code>accessToken</code>) that are
required by the <a>ICE Agent</a> for the Authentication.
</p>
<p>The [[!OAUTH-POP-KEY-DISTRIBUTION]] defines <dfn>alg</dfn>
parameter in Section 4.1 and 6. and describes that if the
<a>Authorization Server</a> doesn't have prior knowledge of the
capabilities of the client, then the <a>OAuth Client</a> needs
to provide information about the <a>ICE Agent</a> HMAC
<a>alg</a> capabilities. This information helps the
<a>Authorization Server</a> to generate the approriate HMAC key.
The HMAC <a>alg</a> defines the input key length, and HMAC
algorithm Familly (e.g. SHA), and HMAC algorithm type (e.g.
symmetric/asymmetric).
</p>
<p>The <a>OAuth Client</a> sends an <code>OAuth Request</code>
to the <a>Authorization Server</a> with OAuth param <a>alg</a>
and further OAuth related parameters, to get an <code>OAuth
Response</code> with the <code>access_token</code>,
<code>key</code>, <code>kid</code>, and further OAuth related
parameters.
</p>
<p>However, this specification uses a simplified <a>alg</a>
approach. The length of the HMAC key
(<code>RTCOAuthCredential.macKey</code>) MAY be any integer number of
bytes greater than 20 (160 bits). This negates the need to query the HMAC
Algorithm capabilities of the <a>ICE Agent</a>, and still
allows for hash agility as described by [[STUN-BIS]], Section
15.3.</p>
<div class="note">According to [[!RFC7635]] Section 4.1, the
HMAC key MUST be a symmetric key.
</div>
<p>Currently the STUN/TURN protocols use only SHA-1 and SHA-2
family hash algorithms for Message Integrity Protection, as
defined in [[!RFC5389]] Section 15.4, and [[!STUN-BIS]]
Section 14.6.
</p>
<p>When [[!RFC7635]] is used in WebRTC context, this
specification adds the following additional consideration to
it.
</p>
<p>The <a>OAuth Client</a> SHOULD obtain the mac_key by
requesting an <a>alg</a> value of <code>HS256</code>. This will
result in a 256-bit HMAC key.
</p>
<p><code>HS256</code> is defined in [[!RFC7518]] Section 3.1.
It is recommended here because:
</p>
<ul>
<li>The OAuth respose key parameter is received in JWK format
according to [[!OAUTH-POP-KEY-DISTRIBUTION]] Section 4.2.
JWK's algorithms are normatively registered in the IANA
"JSON Web Signature and Encryption Algorithms" registry.
</li>
<li>STUN/TURN currently use SHA family HMAC algorithms only.
</li>
<li>The key MUST be symmetric, according to [[!RFC7635]].</li>
<li>A 256-bit key is large enough to support all currently
defined STUN message integrity attributes.</li>
</ul>
<p>More details about OAuth PoP Client can be found in
[[!OAUTH-POP-KEY-DISTRIBUTION]] Section 4.
</p>
<p>
More details about <code>Access-Token</code> can be found in
[[!RFC7635]], Section 6.2.
</p>
</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4><dfn>RTCOAuthCredential</dfn> Dictionary</h4>
<p>The <code>RTCOAuthCredential</code> dictionary is used to describe
the OAuth auth credential information which is used by the STUN/TURN
client (inside the <a>ICE Agent</a>) to authenticate against a STUN/TURN
server, as described in [[!RFC7635]]. Note that the <code>kid</code>
parameter is not located in this dictionary, but in
<code>RTCIceServer</code>'s <code>username</code> member.
</p>
<div>
<pre class="idl">dictionary RTCOAuthCredential {
required DOMString macKey;
required DOMString accessToken;
};</pre>
<section>
<h2>Dictionary <a class="idlType">RTCOAuthCredential</a> Members
</h2>
<dl data-link-for="RTCOAuthCredential"
data-dfn-for="RTCOAuthCredential" class="dictionary-members">
<dt><dfn><code>macKey</code></dfn> of type <span class=
"idlMemberType"><a>DOMString</a></span>, required</dt>
<dd>
<p>The "mac_key", as described in [[!RFC7635]], Section 6.2, in
a base64-url encoded format. It is used in STUN message
integrity hash calculation (as the password is used in password
based authentication). Note that the OAuth response "key"
parameter is a JSON Web Key (JWK) or a JWK encrypted with a JWE
format. Also note that this is the only OAuth parameter whose
value is not used directly, but must be extracted from the "k"
parameter value from the JWK, which contains the needed
base64-encoded "mac_key".</p>
</dd>
<dt><dfn><code>accessToken</code></dfn> of type <span class=
"idlMemberType"><a>DOMString</a></span>, required</dt>
<dd>
<p>The "access_token", as described in [[!RFC7635]], Section
6.2, in a base64-encoded format. This is an encrypted
self-contained token that is opaque to the application.
Authenticated encryption is used for message encryption and
integrity protection. The access token contains a non-encrypted
nonce value, which is used by the Authorization Server for unique
mac_key generation. The second part of the token is protected
by Authenticated Encryption. It contains the mac_key, a
timestamp and a lifetime. The timestamp combined with lifetime
provides expiry information; this information describes the
time window during which the token credential is valid and
accepted by the TURN server.
</p>
</dd>
</dl>
</section>
</div>
<p>An example of an RTCOAuthCredential dictionary is:</p>
<pre class="example highlight"><code>
{
macKey: 'WmtzanB3ZW9peFhtdm42NzUzNG0=',
accessToken: 'AAwg3kPHWPfvk9bDFL936wYvkoctMADzQ5VhNDgeMR3+ZlZ35byg972fW8QjpEl7bx91YLBPFsIhsxloWcXPhA=='
}
</code></pre>
</section>
<section>
<h4><dfn>RTCIceServer</dfn> 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 or RTCOAuthCredential) 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, and <code>credentialType</code> is
<code>"password"</code>, then this attribute specifies the
username to use with that TURN server.</p>
<p>If this <code><a>RTCIceServer</a></code> object represents a
TURN server, and <code>credentialType</code> is
<code>"oauth"</code>, then this attribute specifies the Key ID
(<code>kid</code>) of the shared symmetric key, which is shared
between the TURN server and the Authorization Server, as described
in [[!RFC7635]]. It is an ephemeral and unique key identifier.
The <code>kid</code> allows the TURN server to select the
appropriate keying material for decryption of the Access-Token,
so the key identified by this <code>kid</code> is used in the
Authenticated Encryption of the "access_token". The
<code>kid</code> value is equal with the OAuth response "kid"
parameter, as defined in [[!RFC7515]] Section 4.1.4.
</p>
</dd>
<dt><dfn><code>credential</code></dfn> of type <span class=
"idlMemberType">(<a>DOMString</a> or <a>RTCOAuthCredential</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>
<p>If <code>credentialType</code> is <code>"password"</code>,
<code>credential</code> is a <a>DOMString</a>, and represents a
long-term authentication password, as described in
[[!RFC5389]], Section 10.2.</p>
<p>If <code>credentialType</code> is <code>"oauth"</code>,
<code>credential</code> is an <a>RTCOAuthCredential</a>, which
contains the OAuth access token and MAC key.</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'},
{urls: 'turns:turn2.example.net',
username: '22BIjxU93h/IgwEb',
credential: {
macKey: 'WmtzanB3ZW9peFhtdm42NzUzNG0=',
accessToken: 'AAwg3kPHWPfvk9bDFL936wYvkoctMADzQ5VhNDgeMR3+ZlZ35byg972fW8QjpEl7bx91YLBPFsIhsxloWcXPhA=='
},
credentialType: 'oauth'}
];
</code></pre>
</section>
<section>
<h4><dfn>RTCIceTransportPolicy</dfn> Enum</h4>
<p>As described 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 (non-normative)</th>
</tr>
<tr>
<td><dfn><code>relay</code></dfn></td>
<td>
<p>
The <a>ICE Agent</a> uses only media relay candidates
such as candidates passing through a TURN server.
</p>
<div class="note">
This can be used to prevent the remote endpoint from learning
the user's IP addresses, which may be desired in certain
use cases. For example, in a "call"-based application, the
application may want to prevent an unknown caller from
learning the callee's IP addresses until the callee has
consented in some way.
</div>
</td>
</tr>
<tr>
<td><dfn><code>all</code></dfn></td>
<td>
<p>
The <a>ICE Agent</a> can use any type of candidate when
this value is specified.
</p>
<div class="note">
The implementation can still use its own candidate
filtering policy in order to limit the IP addresses exposed
to the application, as noted in the description of
<code>RTCIceCandidate.<a data-link-for="RTCIceCandidate">ip</a></code>.
</div>
</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4><dfn>RTCBundlePolicy</dfn> 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><dfn>RTCRtcpMuxPolicy</dfn> 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 {
// At risk due to lack of implementers' interest.
"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. Note that, as stated in <span
data-jsep="constructor">[[!JSEP]]</span>, the user agent
MAY not implement non-multiplexed RTCP, in which case it will
reject attempts to construct an <a>RTCPeerConnection</a> with the
<code>negotiate</code> policy.</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 class="issue atrisk">
<p>Aspects of this specification supporting non-multiplexed RTP/RTCP are marked
as features at risk, since there is no clear commitment from implementers.
This includes:</p>
<ol>
<li>The value <code>negotiate</code>, since there is no clear commitment
from implementers for the behavior associated with this.</li>
<li>Support for the <code>rtcpTransport</code> attribute within the
<code><a>RTCRtpSender</a></code> and <code><a>RTCRtpReceiver</a></code>.</li>
</ol>
</div>
</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 <dfn>RTCOfferAnswerOptions</dfn>
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 <dfn>RTCOfferOptions</dfn> 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, as
described in section 9.1.1.1 of [[!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>
<p>The <dfn>RTCAnswerOptions</dfn> dictionary describe options specific to session description of type <code>answer</code> (none in this version of the specification).</p>
<pre class="idl">
dictionary RTCAnswerOptions : RTCOfferAnswerOptions {
};</pre>
</div>
</section>
</section>
<section>
<h3>State Definitions</h3>
<section>
<h4><dfn>RTCSignalingState</dfn> Enum</h4>
<div>
<pre class="idl">enum RTCSignalingState {
"stable",
"have-local-offer",
"have-remote-offer",
"have-local-pranswer",
"have-remote-pranswer",
"closed"
};</pre>
<table data-link-for="RTCSignalingState" data-dfn-for=
"RTCSignalingState" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description</th>
</tr>
<tr>
<td><dfn><code>stable</code></dfn></td>
<td>There is no offer­answer exchange in progress. This is
also the initial state in which case the local and remote
descriptions are empty.</td>
</tr>
<tr>
<td><dfn><code>have-local-offer</code></dfn></td>
<td>A local description, of type <code>"offer"</code>, has been successfully
applied.</td>
</tr>
<tr>
<td><dfn><code>have-remote-offer</code></dfn></td>
<td>A remote description, of type <code>"offer"</code>, has been
successfully applied.</td>
</tr>
<tr>
<td><dfn><code>have-local-pranswer</code></dfn></td>
<td>A remote description of type <code>"offer"</code> has been successfully
applied and a local description of type <code>"pranswer"</code> has been
successfully applied.</td>
</tr>
<tr>
<td><dfn><code>have-remote-pranswer</code></dfn></td>
<td>A local description of type <code>"offer"</code> has been successfully
applied and a remote description of type <code>"pranswer"</code> has been
successfully applied.</td>
</tr>
<tr>
<td><dfn><code>closed</code></dfn></td>
<td>The <code><a>RTCPeerConnection</a></code> has been closed;
its <a>[[\IsClosed]]</a> slot is <code>true</code>.</td>
</tr>
</tbody>
</table>
</div>
<figure>
<img alt="signalling state transition diagram" src=
"images/peerstates.svg" width="600">
<figcaption>
Non-normative signalling state transitions diagram
</figcaption>
</figure>
<p>An example set of transitions might be:</p>
<dl>
<dt>Caller transition:</dt>
<dd>
<ul>
<li>new RTCPeerConnection(): <code>stable</code></li>
<li>setLocal(offer): <code>have-local-offer</code></li>
<li>setRemote(pranswer): <code>have-remote-pranswer</code></li>
<li>setRemote(answer): <code>stable</code></li>
</ul>
</dd>
<dt>Callee transition:</dt>
<dd>
<ul>
<li>new RTCPeerConnection(): <code>stable</code></li>
<li>setRemote(offer): <code>have-remote-offer</code></li>
<li>setLocal(pranswer): <code>have-local-pranswer</code></li>
<li>setLocal(answer): <code>stable</code></li>
</ul>
</dd>
</dl>
</section>
<section>
<h4><dfn>RTCIceGatheringState</dfn> Enum</h4>
<div>
<pre class="idl">enum RTCIceGatheringState {
"new",
"gathering",
"complete"
};</pre>
<table data-link-for="RTCIceGatheringState" data-dfn-for=
"RTCIceGatheringState" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description</th>
</tr>
<tr>
<td><dfn><code>new</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s are in the
<code>"new"</code> gathering state and none of the transports are
in the <code>"gathering"</code> state, or there are no
transports.</td>
</tr>
<tr>
<td><dfn><code>gathering</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s are in the
<code>"gathering"</code> state.</td>
</tr>
<tr>
<td><dfn><code>complete</code></dfn></td>
<td>At least one <code><a>RTCIceTransport</a></code> exists,
and all <code><a>RTCIceTransport</a></code>s are in the
<code>"completed"</code> gathering state.</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4><dfn>RTCPeerConnectionState</dfn> Enum</h4>
<div>
<pre class="idl">enum RTCPeerConnectionState {
"new",
"connecting",
"connected",
"disconnected",
"failed",
"closed"
};</pre>
<table data-link-for="RTCPeerConnectionState" data-dfn-for=
"RTCPeerConnectionState" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description</th>
</tr>
<tr>
<td><dfn><code>new</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s or
<code><a>RTCDtlsTransport</a></code>s are in the
<code>"new"</code> state and none of the transports are in the
<code>"connecting"</code>, <code>"checking"</code>,
<code>"failed"</code> or <code>"disconnected"</code> state, or all
transports are in the <code>"closed"</code> state, or there are
no transports.</td>
</tr>
<tr>
<td><dfn><code>connecting</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s or
<code><a>RTCDtlsTransport</a></code>s are in the
<code>"connecting"</code> or <code>"checking"</code> state and none
of them is in the <code>"failed"</code> state.</td>
</tr>
<tr>
<td><dfn><code>connected</code></dfn></td>
<td>All <code><a>RTCIceTransport</a></code>s and
<code><a>RTCDtlsTransport</a></code>s are in the
<code>"connected"</code>, <code>"completed"</code> or
<code>"closed"</code> state and at least one of them is in the
<code>"connected"</code> or <code>"completed"</code> state.</td>
</tr>
<tr>
<td><dfn><code>disconnected</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s or
<code><a>RTCDtlsTransport</a></code>s are in the
<code>"disconnected"</code> state and none of them are in the
<code>"failed"</code> or <code>"connecting"</code> or
<code>"checking"</code> state.</td>
</tr>
<tr>
<td><dfn><code>failed</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s or
<code><a>RTCDtlsTransport</a></code>s are in a
<code>"failed"</code> state.</td>
</tr>
<tr>
<td><dfn><code>closed</code></dfn></td>
<td>
The <code><a>RTCPeerConnection</a></code> object's
<a>[[\IsClosed]]</a> slot is <code>true</code>.
</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<h4><dfn>RTCIceConnectionState</dfn> Enum</h4>
<div>
<pre class="idl">enum RTCIceConnectionState {
"new",
"checking",
"connected",
"completed",
"failed",
"disconnected",
"closed"
};</pre>
<table data-link-for="RTCIceConnectionState" data-dfn-for=
"RTCIceConnectionState" class="simple">
<tbody>
<tr>
<th colspan="2">Enumeration description</th>
</tr>
<tr>
<td><dfn><code>new</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s are in the
<code>"new"</code> state and none of them are in the
<code>"checking"</code>, <code>"failed"</code> or
<code>"disconnected"</code> state, or all
<code><a>RTCIceTransport</a></code>s are in the
<code>"closed"</code> state, or there are no transports.</td>
</tr>
<tr>
<td><dfn><code>checking</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s are in the
<code>"checking"</code> state and none of them are in the
<code>"failed"</code> or <code>"disconnected"</code> state.</td>
</tr>
<tr>
<td><dfn><code>connected</code></dfn></td>
<td>All <code><a>RTCIceTransport</a></code>s are in the
<code>"connected"</code>, <code>"completed"</code> or
<code>"closed"</code> state and at least one of them is in the
<code>"connected"</code> state.</td>
</tr>
<tr>
<td><dfn><code>completed</code></dfn></td>
<td>All <code><a>RTCIceTransport</a></code>s are in the
<code>"completed"</code> or <code>"closed"</code> state and at
least one of them is in the <code>"completed"</code> state.</td>
</tr>
<tr>
<td><dfn><code>failed</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s are in the
<code>"failed"</code> state.</td>
</tr>
<tr>
<td><dfn><code>disconnected</code></dfn></td>
<td>Any of the <code><a>RTCIceTransport</a></code>s are in the
<code>"disconnected"</code> state and none of them are in the
<code>"failed"</code> state.</td>
</tr>
<tr>
<td><dfn><code>closed</code></dfn></td>
<td>
The <code><a>RTCPeerConnection</a></code> object's
<a>[[\IsClosed]]</a> slot is <code>true</code>.
</td>
</tr>
</tbody>
</table>
</div>
<p>Note that if an <code><a>RTCIceTransport</a></code> is discarded as
a result of signaling (e.g. RTCP mux or bundling), or created as a
result of signaling (e.g. adding a new <a>media description</a>), the
state may advance directly from one state to another.</p>
</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><code><var>configuration</var>.servers</code> contains information
used to find and access the servers used by ICE. The application can
supply multiple servers of each type, and any TURN server MAY also be
used as a STUN server for the purposes of gathering server reflexive
candidates.</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>The task source for the tasks listed in this section is the
<a>networking task source</a>.</p>
<section>
<h4>Constructor</h4>
<p>When the <dfn id=
"dom-peerconnection"><code>RTCPeerConnection()</code></dfn> constructor