CARVIEW |
WebRTC 1.0: Real-time Communication Between Browsers
W3C Working Draft 27 October 2011
- This version:
- https://www.w3.org/TR/2011/WD-webrtc-20111027/
- Latest published version:
- https://www.w3.org/TR/webrtc/
- Latest editor's draft:
- https://dev.w3.org/2011/webrtc/editor/webrtc.html
- Previous version:
- none
- Editors:
- Adam Bergkvist, Ericsson
- Daniel C. Burnett, Voxeo
- Cullen Jennings, Cisco
- Anant Narayanan, Mozilla
Initial Author of this Specification was Ian Hickson, Google Inc., with the following copyright statement:
© Copyright 2004-2011 Apple Computer, Inc., Mozilla Foundation, and Opera Software ASA. You are granted a license to use, reproduce and create derivative works of this document.
All subsequent changes since 26 July 2011 done by the W3C WebRTC Working Group are under the following Copyright:
© 2011 W3C® (MIT, ERCIM, Keio), All Rights Reserved. Document use rules apply.
For the entire publication on the W3C site the liability and trademark rules apply.
Abstract
This document defines a set of APIs that allow local media, including audio and video, to be requested from a platform, media to be sent over the network to another browser or device implementing the appropriate set of real-time protocols, and media received from another browser or device to be processed and displayed locally. This specification is being developed in conjunction with a protocol specification developed by the IETF RTCWEB group.
Status of This Document
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
This document is a First Public Working Draft and is not complete. It is subject to major changes and, while early experimentations are encouraged, it is therefore not intended for implementation. The API is based on preliminary work done in the WHATWG. The Web Real-Time Communications Working Group expects this specification to evolve significantly based on:
- The outcomes of ongoing exchanges in the companion RTCWEB group at IETF to define the set of protocols that, together with this document, will enable real-time communications in Web browsers.
- Privacy issues that arise when exposing local capabilities and local streams.
- Technical discussions within the group, on the data channel in particular.
- Experience gained through early experimentations.
- Feedback received from other groups and individuals.
As the specification matures, the group hopes to strike the right balance between a low-level API that would enable interested parties to tweak potentially complex system parameters, and a more high-level API that Web developers can use without a priori technical knowledge about real-time communications.
This document was published by the Web Real-Time Communications Working Group as a Working Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to public-webrtc@w3.org (subscribe, archives). All feedback is welcome.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
Table of Contents
1. Introduction
This section is non-normative.
There are a number of facets to video-conferencing in HTML:
- Getting a multimedia stream (video, audio, or both) from local devices (video cameras, microphones, Web cams) or from prerecorded files provided by the user.
- Recording such streams locally.
- Connecting to remote peers using NAT-traversal technologies such as ICE, STUN, and TURN.
- Sending the locally-produced streams to remote peers and receiving streams from remote peers.
- Displaying such streams (both the locally-produced ones and the remotely-obtained
ones) locally using the
video
oraudio
elements. - Sending arbitrary data to remote peers.
This document defines the APIs used for these features. This specification is being developed in conjunction with a protocol specification developed by the IETF RTCWEB group.
2. Obtaining local multimedia content
2.1 Definition
2.1.1 NavigatorUserMedia
[NoInterfaceObject]
interface NavigatorUserMedia {
void getUserMedia (MediaStreamOptions
? options, NavigatorUserMediaSuccessCallback
? successCallback, optional NavigatorUserMediaErrorCallback
? errorCallback);
};
2.1.1.1 Methods
getUserMedia
-
Prompts the user for permission to use their Web cam or other video or audio input.
The options argument is an object of type
MediaStreamOptions
. The object can contain the following boolean properties:- "
audio
" - The provided media needs to include audio data.
- "
video
" - The provided media needs to include video data.
If the user accepts, the successCallback is invoked, with a suitable
LocalMediaStream
object as its argument.If the user declines, the errorCallback (if any) is invoked.
When the
getUserMedia()
method is called, the user agent must run the following steps:-
Let options be the method's first argument.
-
Let successCallback be the callback indicated by the method's second argument.
-
Let errorCallback be the callback indicated by the method's third argument, if any, or null otherwise.
-
If successCallback is null, abort these steps.
-
Let audio be true.
-
Let video be true.
-
If the audio property in options is present and set to false, let audio be false.
-
If the video property in options is present and set to false, let video be false.
-
If both audio and video are still false, then throw a
NOT_SUPPORTED_ERR
exception and abort these steps. -
Return, and run the remaining steps asynchronously.
-
Optionally, e.g. based on a previously-established user preference, for security reasons, or due to platform limitations, jump to the step labeled failure below.
-
Prompt the user in a user-agent-specific manner for permission to provide the entry script's origin with a
LocalMediaStream
object representing a media stream.If audio is true, then the provided media should include an audio track. If audio is false, then the provided media must not include an audio track.
If video is true, then the provided media should include a video track. If video is false, then the provided media must not include a video track.
User agents are encouraged to default to using the user's primary or system default camera and/or microphone (as appropriate) to generate the media stream. User agents may allow users to use any media source, including pre-recorded media files.
User agents may wish to offer the user more control over the provided media. For example, a user agent could offer to enable a camera light or flash, or to change settings such as the frame rate or shutter speed.
If the user grants permission to use local recording devices, user agents are encouraged to include a prominent indicator that the devices are "hot" (i.e. an "on-air" or "recording" indicator).
If the user denies permission, jump to the step labeled failure below. If the user never responds, this algorithm stalls on this step.
-
Let stream be the
LocalMediaStream
object for which the user granted permission. -
Queue a task to invoke successCallback with stream as its argument.
-
Abort these steps.
-
Failure: If errorCallback is null, abort these steps.
-
Let error be a new
NavigatorUserMediaError
object whosecode
attribute has the numeric value 1 (PERMISSION_DENIED
). -
Queue a task to invoke errorCallback with error as its argument.
The task source for these tasks is the user interaction task source.
Parameter Type Nullable Optional Description options MediaStreamOptions
✔ ✘ successCallback NavigatorUserMediaSuccessCallback
✔ ✘ errorCallback NavigatorUserMediaErrorCallback
✔ ✔ No exceptions.Return type:void
- "
Navigator implements NavigatorUserMedia
;
All instances of the Navigator
type are defined to also implement the NavigatorUserMedia
interface.
2.1.2 MediaStreamOptions
[NoInterfaceObject]
interface MediaStreamOptions {
attribute boolean audio;
attribute boolean video;
};
2.1.3 NavigatorUserMediaSuccessCallback
[Callback=FunctionOnly, NoInterfaceObject]
interface NavigatorUserMediaSuccessCallback {
void handleEvent (LocalMediaStream
stream);
};
2.1.3.1 Methods
handleEvent
- (Explanation of handleEvent TBD)
Parameter Type Nullable Optional Description stream LocalMediaStream
✘ ✘ No exceptions.Return type:void
2.1.4 NavigatorUserMediaError and NavigatorUserMediaErrorCallback
[NoInterfaceObject]
interface NavigatorUserMediaError {
const unsigned short PERMISSION_DENIED = 1;
readonly attribute unsigned short code;
};
2.1.4.1 Attributes
code
of type unsigned short, readonly- Returns the current error's error code. At this time, this will always be 1, for
which the constant
PERMISSION_DENIED
is defined.No exceptions.
2.1.4.2 Constants
PERMISSION_DENIED
of type unsigned short- The user denied the page permission to use the user's media devices.
[Callback=FunctionOnly, NoInterfaceObject]
interface NavigatorUserMediaErrorCallback {
void handleEvent (NavigatorUserMediaError
error);
};
2.1.4.3 Methods
handleEvent
- (Explanation of handleEvent TBD)
Parameter Type Nullable Optional Description error NavigatorUserMediaError
✘ ✘ No exceptions.Return type:void
2.2 Examples
A voice chat feature in a game could attempt to get access to the user's microphone by calling the API as follows:
<script> navigator.getUserMedia('audio', gotAudio); function gotAudio(stream) { // ... use 'stream' ... } </script>
A video-conferencing system would ask for both audio and video:
<script> function beginCall() { navigator.getUserMedia('audio,video user', gotStream); } function gotStream(stream) { // ... use 'stream' ... } </script>
3. Stream API
3.1 Introduction
The MediaStream
interface is used to
represent streams of media data, typically (but not necessarily) of audio and/or video
content, e.g. from a local camera or a remote site. The data from a MediaStream
object does not necessarily have a canonical
binary form; for example, it could just be "the video currently coming from the user's
video camera". This allows user agents to manipulate media streams in whatever fashion
is most suitable on the user's platform.
Each MediaStream
object can represent zero
or more tracks, in particular audio and video tracks. Tracks can contain multiple
channels of parallel data; for example a single audio track could have nine channels of
audio data to represent a 7.2 surround sound audio track.
Each track represented by a MediaStream
object has a corresponding MediaStreamTrack
object.
A MediaStream
object has an input and an
output. The input depends on how the object was created: a LocalMediaStream
object generated by a getUserMedia()
call, for instance, might take
its input from the user's local camera, while a MediaStream
created by a PeerConnection
object will take as input the data received
from a remote peer. The output of the object controls how the object is used, e.g. what
is saved if the object is written to a file, what is displayed if the object is used in
a video
element, or indeed what is transmitted to a remote peer if the
object is used with a PeerConnection
object.
Each track in a MediaStream
object can be
disabled, meaning that it is muted in the object's output. All tracks are initially
enabled.
A MediaStream
can be
finished,
indicating that its inputs have forever stopped providing data. When a MediaStream
object is finished, all its tracks are muted
regardless of whether they are enabled or disabled.
The output of a MediaStream
object must
correspond to the tracks in its input. Muted audio tracks must be replaced with
silence. Muted video tracks must be replaced with blackness.
A new MediaStream
object can be created
from a list of MediaStreamTrack
objects
using the MediaStream()
constructor. The list of MediaStreamTrack
objects can be the track list of another stream, a subset of the track list of
a stream or a composition of MediaStreamTrack
objects from different MediaStream
objects.
The ability to duplicate a MediaStream
, i.e.
create a new MediaStream
object from the track
list of an existing stream, allows for greater control since separate
MediaStream
instances can be manipulated and consumed
individually. This can be used, for instance, in a video-conferencing scenario to display
the local video from the user's camera and microphone in a local monitor, while only
transmitting the audio to the remote peer (e.g. in response to the user using a "video
mute" feature). Combining tracks from different MediaStream
objects into a new MediaStream
makes it
possible to, e.g., record selected tracks from a conversation involving several
MediaStream
objects with a single
MediaStreamRecorder
.
The LocalMediaStream
interface is used
when the user agent is generating the stream's data (e.g. from a camera or streaming it
from a local video file). It allows authors to control individual tracks during the
generation of the content, e.g. to allow the user to temporarily disable a local camera
during a video-conference chat.
When a LocalMediaStream
object is being
generated from a local file (as opposed to a live audio/video source), the user agent
should stream the data from the file in real time, not all at once. This reduces the
ease with which pages can distinguish live video from pre-recorded video, which can
help protect the user's privacy.
3.2 Interface definitions
3.2.1 MediaStream
The MediaStream(trackList)
constructor must return a new MediaStream
object with a newly generated label.
A new MediaStreamTrack
object is created
for every unique underlying media source in trackList and appended
to the new MediaStream
object's track list
according to the track ordering constraints.
A MediaStream
object is said to end
when the user agent learns that no more data will ever be forthcoming for this
stream.
When a MediaStream
object ends for any
reason (e.g. because the user rescinds the permission for the page to use the local
camera, or because the data comes from a finite file and the file's end has been
reached and the user has not requested that it be looped, or because the stream comes
from a remote peer and the remote peer has permanently stopped sending data, it is
said to be finished
. When this happens for any reason other than the
stop()
method being invoked, the user agent must
queue a task that runs the following steps:
-
If the object's
readyState
attribute has the valueENDED
(2) already, then abort these steps. (Thestop()
method was probably called just before the stream stopped for other reasons, e.g. the user clicked an in-page stop button and then the user-agent-provided stop button.) -
Set the object's
readyState
attribute toENDED
(2). -
Fire a simple event named
ended
at the object.
As soon as a MediaStream
object is finished, the stream's
tracks start outputting only silence and/or blackness, as appropriate, as defined earlier.
If the end of the stream was reached due to a user request, the task source for this task is the user interaction task source. Otherwise the task source for this task is the networking task source.
[Constructor (in MediaStreamTrackList trackList)]
interface MediaStream {
readonly attribute DOMString label;
readonly attribute MediaStreamTrackList tracks;
MediaStreamRecorder
record ();
const unsigned short LIVE = 1;
const unsigned short ENDED = 2;
readonly attribute unsigned short readyState;
attribute Function? onended;
};
3.2.1.1 Attributes
label
of type DOMString, readonly- Returns a label that is unique to this stream, so that streams can be recognized
after they are sent through the
PeerConnection
API.No exceptions. onended
of type Function, nullable- This event handler, of type
ended
, must be supported by all objects implementing theMediaStream
interface.No exceptions. readyState
of type unsigned short, readonly-
The
readyState
attribute represents the state of the stream. It must return the value to which the user agent last set it (as defined below). It can have the following values: LIVE or ENDED.When a
MediaStream
object is created, itsreadyState
attribute must be set toLIVE
(1), unless it is being created using theMediaStream()
constructor whose argument is a list ofMediaStreamTrack
objects whose underlying media sources will never produce any more data, in which case theMediaStream
object must be created with itsreadyState
attribute set toENDED
(2).No exceptions. tracks
of type MediaStreamTrackList, readonly-
Returns a
MediaStreamTrackList
object representing the tracks that can be enabled and disabled.A
MediaStream
can have multiple audio and video sources (e.g. because the user has multiple microphones, or because the real source of the stream is a media resource with many media tracks). The stream represented by aMediaStream
thus has zero or more tracks.The
tracks
attribute must return an array host object for objects of typeMediaStreamTrack
that is fixed length and read only. The same object must be returned each time the attribute is accessed. [WEBIDL]The array must contain the
MediaStreamTrack
objects that correspond to the the tracks of the stream. The relative order of all tracks in a user agent must be stable. All audio tracks must precede all video tracks. Tracks that come from a media resource whose format defines an order must be in the order defined by the format; tracks that come from a media resource whose format does not define an order must be in the relative order in which the tracks are declared in that media resource. Within these constraints, the order is user-agent defined.No exceptions.
3.2.1.2 Methods
record
-
Begins recording the stream. The returned
MediaStreamRecorder
object provides access to the recorded data.When the
record()
method is invoked, the user agent must return a newMediaStreamRecorder
object associated with the stream.No parameters.No exceptions.Return type:MediaStreamRecorder
3.2.1.3 Constants
ENDED
of type unsigned short- The stream has finished (the user agent is no longer receiving or generating data, and will never receive or generate more data for this stream).
LIVE
of type unsigned short- The stream is active (the user agent is making a best-effort attempt to receive or generate data in real time).
MediaStream
implements EventTarget;
All instances of the
type are defined to also implement the EventTarget interface.MediaStream
3.2.2 LocalMediaStream
interface LocalMediaStream : MediaStream
{
void stop ();
};
3.2.2.1 Methods
stop
-
When a
LocalMediaStream
object'sstop()
method is invoked, the user agent must queue a task that runs the following steps:-
If the object's
readyState
attribute is in theENDED
(2) state, then abort these steps. -
Permanently stop the generation of data for the stream. If the data is being generated from a live source (e.g. a microphone or camera), and no other stream is being generated from a live source, then the user agent should remove any active "on-air" indicator. If the data is being generated from a prerecorded source (e.g. a video file), any remaining content in the file is ignored. The stream is finished. The stream's tracks start outputting only silence and/or blackness, as appropriate, as defined earlier.
-
Set the object's
readyState
attribute toENDED
(2). -
Fire a simple event named
ended
at the object.
The task source for the tasks queued for the
stop()
method is the DOM manipulation task source.No parameters.No exceptions.Return type:void
-
3.2.3 MediaStreamTrack
typedef MediaStreamTrack
[] MediaStreamTrackList;
MediaStreamTrack
type.interface MediaStreamTrack {
readonly attribute DOMString kind;
readonly attribute DOMString label;
attribute boolean enabled;
};
3.2.3.1 Attributes
enabled
of type boolean-
The
MediaStreamTrack.enabled
attribute, on getting, must return the last value to which it was set. On setting, it must be set to the new value, and then, if theMediaStreamTrack
object is still associated with a track, must enable the track if the new value is true, and disable it otherwise.Thus, after a
MediaStreamTrack
is disassociated from its track, itsenabled
attribute still changes value when set, it just doesn't do anything with that new value.No exceptions. kind
of type DOMString, readonly-
The
MediaStreamTrack.kind
attribute must return the string "audio
" if the object's corresponding track is or was an audio track, "video
" if the corresponding track is or was a video track, and a user-agent defined string otherwise.No exceptions. label
of type DOMString, readonly-
When a
LocalMediaStream
object is created, the user agent must generate a globally unique identifier string, and must initialize the object'slabel
attribute to that string. Such strings must only use characters in the ranges U+0021, U+0023 to U+0027, U+002A to U+002B, U+002D to U+002E, U+0030 to U+0039, U+0041 to U+005A, U+005E to U+007E, and must be 36 characters long.When a
MediaStream
is created to represent a stream obtained from a remote peer, thelabel
attribute is initialized from information provided by the remote source.When a
MediaStream
is created from another using theMediaStream()
constructor, thelabel
attribute is initialized to a newly generated value.The
label
attribute must return the value to which it was initialized when the object was created.The label of a
MediaStream
object is unique to the source of the stream, but that does not mean it is not possible to end up with duplicates. For example, a locally generated stream could be sent from one user to a remote peer usingPeerConnection
, and then sent back to the original user in the same manner, in which case the original user will have multiple streams with the same label (the locally-generated one and the one received from the remote peer).User agents may label audio and video sources (e.g. "Internal microphone" or "External USB Webcam"). The
MediaStreamTrack.label
attribute must return the label of the object's corresponding track, if any. If the corresponding track has or had no label, the attribute must instead return the empty string.Thus the
kind
andlabel
attributes do not change value, even if theMediaStreamTrack
object is disassociated from its corresponding track.No exceptions.
3.2.4 MediaStreamRecorder
interface MediaStreamRecorder {
voice getRecordedData (BlobCallback
? callback);
};
3.2.4.1 Methods
getRecordedData
-
Creates a
Blob
of the recorded data, and invokes the provided callback with thatBlob
.When the
getRecordedData()
method is called, the user agent must run the following steps:-
Let callback be the callback indicated by the method's first argument.
-
If callback is null, abort these steps.
-
Let data be the data that was streamed by the
MediaStream
object from which theMediaStreamRecorder
was created since the creation of theMediaStreamRecorder
object. -
Return, and run the remaining steps asynchronously.
-
Generate a file that containing data in a format supported by the user agent for use in
audio
andvideo
elements. -
Let blob be a
Blob
object representing the contents of the file generated in the previous step. [FILE-API] -
Queue a task to invoke callback with blob as its argument.
The
getRecordedData()
method can be called multiple times on oneMediaStreamRecorder
object; each time, it will create a new file as if this was the first time the method was being called. In particular, the method does not stop or reset the recording when the method is called.Parameter Type Nullable Optional Description callback BlobCallback
✔ ✘ No exceptions.Return type:voice
-
3.2.5 BlobCallback
[Callback=FunctionOnly, NoInterfaceObject]
interface BlobCallback {
void handleEvent (Blob blob);
};
3.2.6 URL
Note that the following is actually only a partial interface, but ReSpec does not yet support that.
interface URL {
static DOMString createObjectURL (MediaStream
stream);
};
3.2.6.1 Methods
createObjectURL
-
Mints a Blob URL to refer to the given
MediaStream
.When the
createObjectURL()
method is called with aMediaStream
argument, the user agent must return a unique Blob URL for the givenMediaStream
. [FILE-API]For audio and video streams, the data exposed on that stream must be in a format supported by the user agent for use in
audio
andvideo
elements.A Blob URL is the same as what the File API specification calls a Blob URI, except that anything in the definition of that feature that refers to
File
andBlob
objects is hereby extended to also apply toMediaStream
andLocalMediaStream
objects.Parameter Type Nullable Optional Description stream MediaStream
✘ ✘ No exceptions.Return type:static DOMString
3.3 Examples
This sample code exposes a button. When clicked, the button is disabled and the user is prompted to offer a stream. The user can cause the button to be re-enabled by providing a stream (e.g. giving the page access to the local camera) and then disabling the stream (e.g. revoking that access).
<input type="button" value="Start" onclick="start()" id="startBtn"> <script> var startBtn = document.getElementById('startBtn'); function start() { navigator.getUserMedia('audio,video', gotStream); startBtn.disabled = true; } function gotStream(stream) { stream.onended = function () { startBtn.disabled = false; } } </script>
This example allows people to record a short audio message and upload it to the server. This example even shows rudimentary error handling.
<input type="button" value="⚫" onclick="msgRecord()" id="recBtn"> <input type="button" value="◼" onclick="msgStop()" id="stopBtn" disabled> <p id="status">To start recording, press the ⚫ button.</p> <script> var recBtn = document.getElementById('recBtn'); var stopBtn = document.getElementById('stopBtn'); function report(s) { document.getElementById('status').textContent = s; } function msgRecord() { report('Attempting to access microphone...'); navigator.getUserMedia('audio', gotStream, noStream); recBtn.disabled = true; } var msgStream, msgStreamRecorder; function gotStream(stream) { report('Recording... To stop, press to ◼ button.'); msgStream = stream; msgStreamRecorder = stream.record(); stopBtn.disabled = false; stream.onended = function () { msgStop(); } } function msgStop() { report('Creating file...'); stopBtn.disabled = true; msgStream.onended = null; msgStream.stop(); msgStreamRecorder.getRecordedData(msgSave); } function msgSave(blob) { report('Uploading file...'); var x = new XMLHttpRequest(); x.open('POST', 'uploadMessage'); x.send(blob); x.onload = function () { report('Done! To record a new message, press the ⚫ button.'); recBtn.disabled = false; }; x.onerror = function () { report('Failed to upload message. To try recording a message again, press the ⚫ button.'); recBtn.disabled = false; }; } function noStream() { report('Could not obtain access to your microphone. To try again, press the ⚫ button.'); recBtn.disabled = false; } </script>
This example allows people to take photos of themselves from the local video camera.
<article> <style scoped> video { transform: scaleX(-1); } p { text-align: center; } </style> <h1>Snapshot Kiosk</h1> <section id="splash"> <p id="errorMessage">Loading...</p> </section> <section id="app" hidden> <p><video id="monitor" autoplay></video> <canvas id="photo"></canvas> <p><input type=button value="📷" onclick="snapshot()"> </section> <script> navigator.getUserMedia('video user', gotStream, noStream); var video = document.getElementById('monitor'); var canvas = document.getElementById('photo'); function gotStream(stream) { video.src = URL.getObjectURL(stream); video.onerror = function () { stream.stop(); }; stream.onended = noStream; video.onloadedmetadata = function () { canvas.width = video.videoWidth; canvas.height = video.videoHeight; document.getElementById('splash').hidden = true; document.getElementById('app').hidden = false; }; } function noStream() { document.getElementById('errorMessage').textContent = 'No camera available.'; } function snapshot() { canvas.getContext('2d').drawImage(video, 0, 0); } </script> </article>
4. Peer-to-peer connections
A PeerConnection
allows two users to
communicate directly, browser-to-browser. Communications are coordinated via a
signaling channel provided by script in the page via the server, e.g. using
XMLHttpRequest
.
Calling "new PeerConnection
(configuration,
signalingCallback)" creates a PeerConnection
object.
The configuration string gives the address of a STUN or TURN server to use to establish the connection. [STUN] [TURN]
The allowed formats for this string are:
- "
TYPE 203.0.113.2:3478
" -
Indicates a specific IP address and port for the server.
- "
TYPE relay.example.net:3478
"" -
Indicates a specific host and port for the server; the user agent will look up the IP address in DNS.
- "
TYPE example.net
"" -
Indicates a specific domain for the server; the user agent will look up the IP address and port in DNS.
The "TYPE
" is one of:
STUN
- Indicates a STUN server
STUNS
- Indicates a STUN server that is to be contacted using a TLS session.
TURN
- Indicates a TURN server
TURNS
- Indicates a TURN server that is to be contacted using a TLS session.
The signalingCallback argument is a method that will be invoked
when the user agent needs to send a message to the other host over the signaling
channel. When the callback is invoked, convey its first argument (a string) to the
other peer using whatever method is being used by the Web application to relay
signaling messages. (Messages returned from the other peer are provided back to the
user agent using the processSignalingMessage()
method.)
A PeerConnection
object has an associated
PeerConnection
signaling
callback, a PeerConnection
ICE
Agent,
a PeerConnection
readiness state and an SDP Agent. These
are initialized when the object is created.
When the PeerConnection()
constructor is invoked, the
user agent must run the following steps. This algorithm has a synchronous
section (which is triggered as part of the event loop algorithm).
Steps in the synchronous section are marked with ⌛.
-
Let serverConfiguration be the constructor's first argument.
-
Let signalingCallback be the constructor's second argument.
-
Let connection be a newly created
PeerConnection
object. -
Create an ICE Agent and let connection's
PeerConnection
ICE Agent be that ICE Agent. [ICE] -
If serverConfiguration contains a U+000A LINE FEED (LF) character or a U+000D CARRIAGE RETURN (CR) character (or both), remove all characters from serverConfiguration after the first such character.
-
Split serverConfiguration on spaces to obtain configuration components.
-
If configuration components has two or more components, and the first component is a case-sensitive match for one of the following strings:
- "
STUN
" - "
STUNS
" - "
TURN
" - "
TURNS
"
...then run the following substeps:
-
Let server type be STUN if the first component of configuration components is '
STUN
' or 'STUNS
', and TURN otherwise (the first component of configuration components is "TURN
" or "TURNS
"). -
Let secure be true if the first component of configuration components is "
STUNS
" or "TURNS
", and false otherwise. -
Let host be the contents of the second component of configuration components up to the character before the first U+003A COLON character (:), if any, or the entire string otherwise.
-
Let port be the contents of the second component of configuration components from the character after the first U+003A COLON character (:) up to the end, if any, or the empty string otherwise.
-
Configure the
PeerConnection
ICE Agent's STUN or TURN server as follows:- If server type is STUN, the server is a STUN server. Otherwise, server type is TURN and the server is a TURN server.
- If secure is true, the server is to be contacted using TLS-over-TCP, otherwise, it is to be contacted using UDP.
- The IP address, host name, or domain name of the server is host.
- The port to use is port. If this is the empty string, then only a domain name is configured (and the ICE Agent will use DNS SRV requests to determine the IP address and port).
- The long-term username for the STUN or TURN server is the ASCII serialization of the entry script's origin; the long-term password is the empty string.
If the given IP address, host name, domain name, or port are invalid, then the user agent must act as if no STUN or TURN server is configured.
- "
-
Let the connection's
PeerConnection
signaling callback be signalingCallback. -
Set connection's
PeerConnection
readiness state toNEW
(0). -
Set connection's
PeerConnection
ice state toNEW
(0). -
Set connection's
PeerConnection
sdp state toNEW
(0). -
Let connection's
localStreams
attribute be an empty read-onlyMediaStream
array. [WEBIDL] -
Let connection's
remoteStreams
attribute be an empty read-onlyMediaStream
array. [WEBIDL] -
Return connection, but continue these steps asynchronously.
-
Await a stable state. The synchronous section consists of the remaining steps of this algorithm. (Steps in synchronous sections are marked with ⌛.)
-
⌛ If the ice state is set to NEW, it must queue a task to start gathering ICE address and set the ice state to ICEGATHERING.
-
⌛ Once the ICE address gathering is complete, if there are any streams in localStreams, the SDP Agent will send the initial the SDP offer. The initial SDP offer must contain both the ICE candidate information as well as the SDP to represent the media descriptions for all the streams in localStreams.
During the lifetime of the peerConnection object, the following procedures are followed:
-
If a local media stream has been added and an SDP offer needs to be sent, and the ICE state is not NEW or ICEGATHERING, and the SDP Agent state is NEW or SDPIDLE, then send and queue a task to send an SDP offer and change the SPD state to SDP Waiting.
-
If an SDP offer has been received, and the SDP state is NEW or SDPIDLE, pass the ICE candidates from the SDP offer to the ICE Agent and change it state to ICECHECKING. Construct an appropriate SDP answer, update the remote streams, queue a task to send the SDP offer, and set the SDPAgent state to SDPIDLE.
-
At the point the sdpState changes from NEW to some other state, the readyState changes to NEGOTIATING.
-
If the ICE Agent finds a candidates that froms a valid connection, the ICE state is changed to ICECONNECTED
-
If the ICE Agent finishes checking all candidates, if a connection has been found, the ice state is changed to ICECOMPLETED and if not connection has been found it is changed to ICEFAILED.
-
If the iceState is ICECONNECTED or ICECOMPLETED and the SDP stat is SDPIDLE, the readyState is set to ACTIVE.
-
If the iceState is ICEFAILED, a task is queued to calls the close method.
-
The close method will cause the system to wait until the sdpStat is SDPIDLE then it will send an SDP offer terminating all media and change the readyState to CLOSING as well as stop all ICE process and change the iceState to ICE_CLOSED. Once an SDP anser to this offer is received, the readyState will be changed to CLOSED.
User agents may negotiate any codec and any resolution, bitrate, or other quality
metric. User agents are encouraged to initially negotiate for the native resolution of
the stream. For streams that are then rendered (using a video
element),
user agents are encouraged to renegotiate for a resolution that matches the rendered
display size.
Starting with the native resolution means that if the Web application
notifies its peer of the native resolution as it starts sending data, and the peer
prepares its video
element accordingly, there will be no need for a
renegotiation once the stream is flowing.
All SDP media descriptions for streams represented by MediaStream
objects must include a label attribute
("a=label:
") whose value is the value of the MediaStream
object's label
attribute.
[SDP] [SDPLABEL]
PeerConnection
s must not generate any
candidates for media streams whose media descriptions do not have a label attribute
("a=label:
"). [ICE] [SDP] [SDPLABEL]
When a user agent starts receiving media for a component and a candidate was
provided for that component by a PeerConnection
, the user agent must follow these
steps:
-
Let connection be the
PeerConnection
expecting this media. -
If there is already a
MediaStream
object for the media stream to which this component belongs, then associate the component with that media stream and abort these steps. (Some media streams have multiple components; this API does not expose the role of these individual components in ICE.) -
Create a
MediaStream
object to represent the media stream. Set itslabel
attribute to the value of the SDP Label attribute for that component's media stream. -
Queue a task to run the following substeps:
-
If the connection's
PeerConnection
readiness state isCLOSED
(3), abort these steps. -
Add the newly created
MediaStream
object to the end of connection'sremoteStreams
array. -
Fire a stream event named
addstream
with the newly createdMediaStream
object at the connection object.
-
When a PeerConnection
finds that a stream
from the remote peer has been removed (its port has been set to zero in a media
description sent on the signaling channel), the user agent must follow these steps:
-
Let connection be the
PeerConnection
associated with the stream being removed. -
Let stream be the
MediaStream
object that represents the media stream being removed, if any. If there isn't one, then abort these steps. -
By definition, stream is now finished.
A task is thus queued to update stream and fire an event.
-
Queue a task to run the following substeps:
-
If the connection's
PeerConnection
readiness state isCLOSED
(3), abort these steps. -
Remove stream from connection's
remoteStreams
array. -
Fire a stream event named
removestream
with stream at the connection object.
-
The task source for the tasks listed in this section is the networking task source.
To prevent network sniffing from allowing a fourth party to establish a connection to a peer using the information sent out-of-band to the other peer and thus spoofing the client, the configuration information should always be transmitted using an encrypted connection.
4.1 PeerConnection
[Constructor (in DOMString configuration, in SignalingCallback signalingCallback)]
interface PeerConnection {
void processSignalingMessage (DOMString message);
const unsigned short NEW = 0;
const unsigned short NEGOTIATING = 1;
const unsigned short ACTIVE = 2;
const unsigned short CLOSING = 4;
const unsigned short CLOSED = 3;
readonly attribute unsigned short readyState;
const unsigned short ICE_GATHERING = 0x100;
const unsigned short ICE_WAITING = 0x200;
const unsigned short ICE_CHECKING = 0x300;
const unsigned short ICE_CONNECTED = 0x400;
const unsigned short ICE_COMPLETED = 0x500;
const unsigned short ICE_FAILED = 0x600;
const unsigned short ICE_CLOSED = 00x700;
readonly attribute unsigned short iceState;
const unsigned short SDP_IDLE = 0x1000;
const unsigned short SDP_WAITING = 0x2000;
const unsigned short SDP_GLARE = 0x3000;
readonly attribute unsigned short sdpState;
void addStream (MediaStream
stream, MediaStreamHints hints);
void removeStream (MediaStream
stream);
readonly attribute MediaStream
[] localStreams;
readonly attribute MediaStream
[] remoteStreams;
void close ();
attribute Function? onconnecting;
attribute Function? onopen;
attribute Function? onstatechange;
attribute Function? onaddstream;
attribute Function? onremovestream;
};
4.1.1 Attributes
iceState
of type unsigned short, readonly-
The
iceState
attribute must return the state of thePeerConnection
ICE AgentPeerConnection
ICE state, represented by a number from the following list:PeerConnection
.NEW
(0)- The object was just created, and no networking has yet occurred.
PeerConnection
.ICE_GATHERING
(0x100)- The ICE Agent is attempting to establish a gather addresses.
PeerConnection
.ICE_WAITING
(0x200)- The ICE Agent is waiting for candidates from the other side before it can start checking.
PeerConnection
.ICE_CHECKING
(0x300)- The ICE Agent is checking candidates but has not yet found a connection.
PeerConnection
.ICE_CONNECTED
(0x400)- The ICE Agent has found a connection but is still checking other candidates to see if there is a better connection.
PeerConnection
.ICE_COMPLETED
(0x500)- The ICE Agent has finished checking and found a connection.
PeerConnection
.ICE_FAILED
(0x600)- The ICE Agent is finished checking all candidates and failed to find a connection.
PeerConnection
.ICE_CLOSED
(0x700)- The ICE Agent has shut down and is no longer responding to STUN requests.
No exceptions. localStreams
of type array ofMediaStream
, readonly-
Returns a live array containing the streams that the user agent is currently attempting to transmit to the remote peer (those that were added with
addStream()
).Specifically, it must return the read-only
MediaStream
array that the attribute was set to when thePeerConnection
's constructor ran.No exceptions. onaddstream
of type Function, nullable- This event handler, of event handler event
type
addstream
, must be supported by all objects implementing thePeerConnection
interface.No exceptions. onconnecting
of type Function, nullable- This event handler, of event handler event
type
connecting
, must be supported by all objects implementing thePeerConnection
interface.No exceptions. onopen
of type Function, nullable- This event handler, of event handler event
type
open
, must be supported by all objects implementing thePeerConnection
interface.No exceptions. onremovestream
of type Function, nullable- This event handler, of event handler event
type
removestream
, must be supported by all objects implementing thePeerConnection
interface.No exceptions. onstatechange
of type Function, nullable- This event handler, of event handler event
type
open
, must be supported by all objects implementing thePeerConnection
interface. It is called any time the readyState, iceState, or sdpState changes.No exceptions. readyState
of type unsigned short, readonly-
The
readyState
attribute must return thePeerConnection
object'sPeerConnection
readiness state, represented by a number from the following list:PeerConnection
.NEW
(0)- The object was just created, and no networking has yet occurred.
PeerConnection
.NEGOTIATING
(1)- The user agent is attempting to establish an connection with the ICE Agent and to negotiate codecs with the SDP Agent.
PeerConnection
.ACTIVE
(2)- The ICE Agent has found a connection the SDP Agent has performed a round of codec negotiation. It is possible for whatever media was negotiated to flow.
PeerConnection
.CLOSING
(4)- The
PeerConnection
object is terminating all media and is in the process of closing the Ice Agent and SDP Agent. PeerConnection
.CLOSED
(3)- The connection is closed.
No exceptions. remoteStreams
of type array ofMediaStream
, readonly-
Returns a live array containing the streams that the user agent is currently receiving from the remote peer.
Specifically, it must return the read-only
MediaStream
array that the attribute was set to when thePeerConnection
's constructor ran.This array is updated when
addstream
andremovestream
events are fired.No exceptions. sdpState
of type unsigned short, readonly-
The
sdpState
attribute must return the state of thePeerConnection
SDP Agent , represented by a number from the following list:PeerConnection
.NEW
(0)- The object was just created, and no networking has yet occurred.
PeerConnection
.SDP_IDLE
(0x1000)- At least one SDP offer or answer has been exchange and the SDP Agent is ready to send an SDP offer or receive an SDP answer.
PeerConnection
.SDP_WAITING
(0x2000)- The SDP Agent has sent and offer and is waiting for a answer.
PeerConnection
.SDP_GLARE
(0x3000)- The SDP Agent received an offer while waiting for an answer and now much wait a rondom amount of time before retrying to send the offer.
No exceptions.
4.1.2 Methods
addStream
-
Attempts to starting sending the given stream to the remote peer. The format for the MediaStreamHints objects is currently undefined by the specification.
When the other peer starts sending a stream in this manner, an
addstream
event is fired at thePeerConnection
object.When the
addStream()
method is invoked, the user agent must run the following steps:-
Let stream be the method's first argument.
-
Let hints be the method's second argument.
-
If the
PeerConnection
object'sPeerConnection
readiness state isCLOSED
(3), throw anINVALID_STATE_ERR
exception. -
If stream is already in the
PeerConnection
object'slocalStreams
object, then abort these steps. -
Add stream to the end of the
PeerConnection
object'slocalStreams
object. -
Return from the method.
-
Parse the hints provided by the application and apply them to the MediaStream, if possible.
-
Have the
PeerConnection
add a media stream for stream the next time the user agent provides a stable state. Any other pending stream additions and removals must be processed at the same time.
Parameter Type Nullable Optional Description stream MediaStream
✘ ✘ hints MediaStreamHints
✘ ✘ No exceptions.Return type:void
-
close
-
When the
close()
method is invoked, the user agent must run the following steps:-
If the
PeerConnection
object'sPeerConnection
readiness state isCLOSED
(3), throw anINVALID_STATE_ERR
exception. -
Destroy the
PeerConnection
ICE Agent, abruptly ending any active ICE processing and any active streaming, and releasing any relevant resources (e.g. TURN permissions). -
Set the object's
PeerConnection
readiness state toCLOSED
(3).
The
localStreams
andremoteStreams
objects remain in the state they were in when the object was closed.No parameters.No exceptions.Return type:void
-
processSignalingMessage
-
When a message is relayed from the remote peer over the signaling channel is received by the Web application, pass it to the user agent by calling the
processSignalingMessage()
method.The order of messages is important. Passing messages to the user agent in a different order than they were generated by the remote peer's user agent can prevent a successful connection from being established or degrade the connection's quality if one is established.
When the
processSignalingMessage()
method is invoked, the user agent must run the following steps:-
Let message be the method's argument.
-
Let connection be the
PeerConnection
object on which the method was invoked. -
If connection's
PeerConnection
readiness state isCLOSED
(3), throw anINVALID_STATE_ERR
exception. -
If the first four characters of message are not "
SDP
" followed by a U+000A LINE FEED (LF) character, then abort these steps. (This indicates an error in the signaling channel implementation. User agents may report such errors to their developer consoles to aid debugging.)Future extensions to the
PeerConnection
interface might use other prefix values to implement additional features. -
Let sdp be the string consisting of all but the first four characters of message.
-
Pass the sdp to the
PeerConnection
SDP Agent as a subsequent offer or answer, to be interpreted as appropriate given the current state of the SDP Agent. [ICE]
When a
PeerConnection
ICE Agent forms a connection to the the far side and enters the state ICECONNECTED, the user agent must queue a task that sets thePeerConnection
object'sPeerConnection
readiness state toACTIVE
(2) and then fires a simple event namedopen
at thePeerConnection
object.Parameter Type Nullable Optional Description message DOMString
✘ ✘ No exceptions.Return type:void
-
removeStream
-
Stops sending the given stream to the remote peer.
When the other peer stops sending a stream in this manner, a
removestream
event is fired at thePeerConnection
object.When the
removeStream()
method is invoked, the user agent must run the following steps:-
Let stream be the method's argument.
-
If the
PeerConnection
object'sPeerConnection
readiness state isCLOSED
(3), throw anINVALID_STATE_ERR
exception. -
If stream is not in the
PeerConnection
object'slocalStreams
object, then abort these steps. -
Remove stream from the
PeerConnection
object'slocalStreams
object. -
Return from the method.
-
Have the
PeerConnection
remove the media stream for stream the next time the user agent provides a stable state. Any other pending stream additions and removals must be processed at the same time.
Parameter Type Nullable Optional Description stream MediaStream
✘ ✘ No exceptions.Return type:void
-
4.1.3 Constants
ACTIVE
of type unsigned short- A connection has been formed and if any media streams were successfully negotiated, any relevant media can be streaming.
CLOSED
of type unsigned short- The
close()
method has been invoked. CLOSING
of type unsigned short- The object is starting to shut down after the
close()
method has been invoked. ICE_CHECKING
of type unsigned short- The ICE Agent is checking candidates but has not yet found a connection that works.
ICE_CLOSED
of type unsigned short- The ICE Agent is terminating and will no longer repined to STUN connectivity checks.
ICE_COMPLETED
of type unsigned short- The ICE Agent has finished checking all candidates and a connection has been formed.
ICE_CONNECTED
of type unsigned short- The ICE Agent has found at least one candidate that works but is still checking.
ICE_FAILED
of type unsigned short- The ICE Agent has finished checking all candidates and no connection was worked.
ICE_GATHERING
of type unsigned short- The ICE Agent is gather addresses that can be used.
ICE_WAITING
of type unsigned short- THE ICE Agent has complete gathering addresses and is waiting for candidates to start checking.
NEGOTIATING
of type unsigned short- The peerConenction object is attempting to get to the point wehre media can flow.
NEW
of type unsigned short- The object was just created and its ICE and SDP Agent have not yet been started.
SDP_GLARE
of type unsigned short- Both side sent SDP offers at the same time and the SDP Agent is waiting to be able to retransmit the SDP offer.
SDP_IDLE
of type unsigned short- A valid offer anser pair has been exchanged and the SDP Agent is waiting for the next SDP transaction.
SDP_WAITING
of type unsigned short- The SDP Agent has sent an SDP offer and is waiting for a response.
PeerConnection
implements EventTarget;
All instances of the
type are defined to also implement the EventTarget interface.PeerConnection
4.2 SignalingCallback
[Callback=FunctionOnly, NoInterfaceObject]
interface SignalingCallback {
void handleEvent (DOMString message, PeerConnection
source);
};
4.2.1 Methods
handleEvent
- Def TBD
Parameter Type Nullable Optional Description message DOMString
✘ ✘ source PeerConnection
✘ ✘ No exceptions.Return type:void
4.3 Examples
When two peers decide they are going to set up a connection to each other, they both go through these steps. The STUN/TURN server configuration describes a server they can use to get things like their public IP address or to set up NAT traversal. They also have to send data for the signaling channel to each other using the same out-of-band mechanism they used to establish that they were going to communicate in the first place.
// the first argument describes the STUN/TURN server configuration var local = new PeerConnection('TURNS example.net', sendSignalingChannel); local.signalingChannel(...); // if we have a message from the other side, pass it along here // (aLocalStream is some LocalMediaStream object) local.addStream(aLocalStream); // start sending video function sendSignalingChannel(message) { ... // send message to the other side via the signaling channel } function receiveSignalingChannel (message) { // call this whenever we get a message on the signaling channel local.signalingChannel(message); } local.onaddstream = function (event) { // (videoElement is some <video> element) videoElement.src = URL.getObjectURL(event.stream); };
5. The data stream
Although progress is being made, there is currently not enough agreement on the data channel to write it up. This section will be filled in as rough consensus is reached.
6. Garbage collection
A Window
object has a strong reference to any PeerConnection
objects created from the constructor whose
global object is that Window
object.
7. Event definitions
The addstream
and removestream
events use the MediaStreamEvent
interface:
7.1 MediaStreamEvent
Firing a stream event
named e with a MediaStream
stream means that an event
with the name e, which does not bubble (except where otherwise
stated) and is not cancelable (except where otherwise stated), and which uses the
MediaStreamEvent
interface with the
stream
attribute set to stream, must be created and dispatched at the given target.
interface MediaStreamEvent : Event {
readonly attribute MediaStream
? stream;
void initMediaStreamEvent (DOMString typeArg, boolean canBubbleArg, boolean cancelableArg, MediaStream
? streamArg);
};
7.1.1 Attributes
stream
of typeMediaStream
, readonly, nullable-
The
stream
attribute represents theMediaStream
object associated with the event.No exceptions.
7.1.2 Methods
initMediaStreamEvent
-
The
initMediaStreamEvent()
method must initialize the event in a manner analogous to the similarly-named method in the DOM Events interfaces. [DOM-LEVEL-3-EVENTS]Parameter Type Nullable Optional Description typeArg DOMString
✘ ✘ canBubbleArg boolean
✘ ✘ cancelableArg boolean
✘ ✘ streamArg MediaStream
✔ ✘ No exceptions.Return type:void
8. Event summary
This section is non-normative.
The following event fires on MediaStream
objects:
Event name | Interface | Fired when... |
---|---|---|
ended |
Event |
The MediaStream object will no longer
stream any data, either because the user revoked the permissions, or because the
source device has been ejected, or because the remote peer stopped sending data,
or because the stop() method was invoked. |
The following events fire on PeerConnection
objects:
Event name | Interface | Fired when... |
---|---|---|
connecting |
Event |
The ICE Agent has begun negotiating with the peer. This can happen multiple
times during the lifetime of the PeerConnection object. |
open |
Event |
The ICE Agent has finished negotiating with the peer. |
message |
MessageEvent |
A data UDP media stream message (to be defined) was received. |
addstream |
MediaStreamEvent |
A new stream has been added to the remoteStreams array. |
removestream |
MediaStreamEvent |
A stream has been removed from the remoteStreams array. |
9. application/html-peer-connection-data
This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
- Type name:
- application
- Subtype name:
- html-peer-connection-data
- Required parameters:
- No required parameters
- Optional parameters:
- No optional parameters
- Encoding considerations:
- This MIME type defines a binary protocol format which uses UTF-8 for text encoding.
- Security considerations:
-
This format is used for encoding UDP packets transmitted by potentially hostile Web page content via a trusted user agent to a destination selected by a potentially hostile remote server. To prevent this mechanism from being abused for cross-protocol attacks, all the data in these packets is masked so as to appear to be random noise. The intent of this masking is to reduce the potential attack scenarios to those already possible previously.
However, this feature still allows random data to be sent to destinations that might not normally have been able to receive them, such as to hosts within the victim's intranet. If a service within such an intranet cannot handle receiving UDP packets containing random noise, it might be vulnerable to attack from this feature.
- Interoperability considerations:
- Rules for processing both conforming and non-conforming content are defined in this specification.
- Published specification:
- This document is the relevant specification.
- Applications that use this media type:
- This type is only intended for use with SDP. [SDP]
- Additional information:
-
- Magic number(s):
- No sequence of bytes can uniquely identify data in this format, as all data in this format is intentionally masked to avoid cross-protocol attacks.
- File extension(s):
- This format is not for use with files.
- Macintosh file type code(s):
- This format is not for use with files.
- Person & email address to contact for further information:
- Daniel C. Burnett <dburnett@voxeo.com>
- Intended usage:
- Common
- Restrictions on usage:
- No restrictions apply.
- Author:
- Daniel C. Burnett <dburnett@voxeo.com>
- Change controller:
- W3C
Fragment identifiers cannot be used with application/html-peer-connection-data
as URLs cannot be used to identify streams that use this format.
A. Acknowledgements
The editors wish to thank the Working Group chairs, Harald Alvestrand and Stefan Håkansson, for their support.
B. References
B.1 Normative references
- [DOM-LEVEL-3-EVENTS]
- Björn Höhrmann; Tom Pixley; Philippe Le Hégaret. Document Object Model (DOM) Level 3 Events Specification. 31 May 2011. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2011/WD-DOM-Level-3-Events-20110531/
- [FILE-API]
- Arun Ranganathan. File API. 17 November 2009. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2009/WD-FileAPI-20091117/
- [ICE]
- J. Rosenberg Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols. April 2010. Internet RFC 5245. URL: https://tools.ietf.org/html/rfc5245
- [SDP]
- J. Rosenberg, H. Schulzrinne. An Offer/Answer Model with the Session Description Protocol (SDP). June 2002. Internet RFC 3264. URL: https://tools.ietf.org/html/rfc3264
- [SDPLABEL]
- O. Levin, G. Camarillo. The Session Description Protocol (SDP) Label Attribute. August 2006. Internet RFC 4574. URL: https://tools.ietf.org/html/rfc4574
- [STUN]
- J. Rosenberg, R. Mahy, P. Matthews, D. Wing. Session Traversal Utilities for NAT (STUN). October 2008. Internet RFC 5389. URL: https://tools.ietf.org/html/rfc5389
- [TURN]
- P. Mahy, P. Matthews, J. Rosenberg. Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN). April 2010. Internet RFC 5766. URL: https://tools.ietf.org/html/rfc5766
- [WEBIDL]
- Cameron McCormack. Web IDL. 19 December 2008. W3C Working Draft. (Work in progress.) URL: https://www.w3.org/TR/2008/WD-WebIDL-20081219
B.2 Informative references
No informative references.