RTCConfiguration - Web APIs
icetransportpolicy optional the current ice transport policy; this must be one of the values from the rtcicetransportpolicy enumeration.
... 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.

RTCConfiguration.iceTransportPolicy - Web APIs
its value must come from the rtcicetransportpolicy enumerated type.

RTCPeerConnection() - Web APIs
icetransportpolicy optional the current ice transport policy; this must be one of the values from the rtcicetransportpolicy enum.

RTCPeerConnection - Web APIs
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.