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The RTCConfiguration dictionary is used to provide configuration options for an RTCPeerConnection. It may be passed into the constructor when instantiating a connection, or used with the RTCPeerConnection.getConfiguration() and RTCPeerConnection.setConfiguration() methods, which allow inspecting and changing the configuration while a connection is established.

The options include ICE server and transport settings and identity information.


bundlePolicy Optional
Specifies how to handle negotiation of candidates when the remote peer is not compatible with the SDP BUNDLE standard. This must be one of the values from the enum RTCBundlePolicy. If this value isn't included in the dictionary, "balanced" is assumed.
certificates Optional
An Array of objects of type RTCCertificate which are used by the connection for authentication. If this property isn't specified, a set of certificates is generated automatically for each RTCPeerConnection instance. Although only one certificate is used by a given connection, providing certificates for multiple algorithms may improve the odds of successfully connecting in some circumstances. See Using certificates below for additional information.
This configuration option cannot be changed after it is first specified; once the certificates have been set, this property is ignored in future calls to RTCPeerConnection.setConfiguration().
iceCandidatePoolSize Optional
An unsigned 16-bit integer value which specifies the size of the prefetched ICE candidate pool. The default value is 0 (meaning no candidate prefetching will occur). You may find in some cases that connections can be established more quickly by allowing the ICE agent to start fetching ICE candidates before you start trying to connect, so that they're already available for inspection when RTCPeerConnection.setLocalDescription() is called.
Changing the size of the ICE candidate pool may trigger the beginning of ICE gathering.
iceServers Optional
An array of RTCIceServer objects, each describing one server which may be used by the ICE agent; these are typically STUN and/or TURN servers. If this isn't specified, the ICE agent may choose to use its own ICE servers; otherwise, the connection attempt will be made with no STUN or TURN server available, which limits the connection to local peers.
iceTransportPolicy Optional
The current ICE transport policy; this must be one of the values from the RTCIceTransportPolicy enum. If this isn't specified, "all" is assumed.
peerIdentity Optional
A DOMString which specifies the target peer identity for the RTCPeerConnection. If this value is set (it defaults to null), the RTCPeerConnection will not connect to a remote peer unless it can successfully authenticate with the given name.
rtcpMuxPolicy Optional
The RTCP mux policy to use when gathering ICE candidates, in order to support non-multiplexed RTCP. The value must be one of those from the RTCRtcpMuxPolicy enum. The default is "require".


RTCBundlePolicy enum

The RTCBundlePolicy enum defines string constants which are used to request a specific policy for gathering ICE candidates if the remote peer isn't compatible with the SDP BUNDLE standard for bundling multiple media streams on a single transport link.

In technical terms, a BUNDLE lets all media flows between two peers flow across a single 5-tuple; that is, from the same IP and port on one peer to the same IP and port on the other peer, using the same transport protocol.

Constant Description
"balanced" On BUNDLE-aware connections, the ICE agent should gather candidates for all of the media types in use (audio, video, and data). Otherwise, the ICE agent should only negotiate one audio and video track on separate transports.
"max-compat" The ICE agent should gather candidates for each track, using separate transports to negotiate all media tracks for connections which aren't BUNDLE-compatible.
"max-bundle" The ICE agent should gather candidates for just one track. If the connection isn't BUNDLE-compatible, then the ICE agent should negotiate just one media track.

RTCIceTransportPolicy enum

The RTCIceTransportPolicy enum defines string constants which can be used to limit the transport policies of the ICE candidates to be considered during the connection process.

Constant Description
"public" Only ICE candidates with public IP addresses will be considered.
"relay" Only ICE candidates whose IP addresses are being relayed, such as those being passed through a TURN server, will be considered.
"all" All ICE candidates will be considered.

RTCRtcpMuxPolicy enum

The RTCRtcpMuxPolicy enum defines string constants which specify what ICE candidates are gathered to support non-multiplexed RTCP. <<<add a link to info about multiplexed RTCP.

Constant Description
"negotiate" Instructs the ICE agent to gather both RTP and RTCP candidates. If the remote peer can multiplex RTCP, then RTCP candidates are multiplexed atop the corresponding RTP candidates. Otherwise, both the RTP and RTCP candidates are returned, separately.
"relay" Tells the ICE agent to gather ICE candidates for only RTP, and to multiplex RTCP atop them. If the remote peer doesn't support RTCP multiplexing, then session negotiation fails.

Using certificates

When you wish to provide your own certificates for use by an RTCPeerConnection instead of having the RTCPeerConnection generate them automatically, you do so through calls to RTCPeerConnection.generateCertificate().

This attribute supports providing multiple certificates because even though a given DTLS connection uses only one certificate, providing multiple certificates allows support for multiple encryption algorithms. The implementation of RTCPeerConnection will choose which certificate to use based on the algorithms it and the remote peer support, as determined during DTLS handshake.

If you don't provide certificates, new ones are generated automatically. One obvious benefit to providing your own is identity key continuity—if you use the same certificate for subsequent calls, the remote peer can tell you're the same caller. This also avoids the cost of generating new keys.

<<<link to added info on identity>>>


The configuration below establishes two ICE servers. The first one, stun:stun.services.mozilla.com, requires authentication, so the username and password are provided. The second server has two URLs: stun:stun.example.com and stun:stun-1.example.com.

var configuration = { iceServers: [{
                          urls: "stun:stun.services.mozilla.com",
                          username: "louis@mozilla.com", 
                          credential: "webrtcdemo"
                      }, {
                          urls: ["stun:stun.example.com", "stun:stun-1.example.com"]

var pc = new RTCPeerConnection(configuration);


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API Dictionary Interface Reference RTCConfiguration WebRTC