stackoverflow.com/questions/18897917/does-webrtc-u...
Q: Does WebRTC use TCP or UDP as its peer-to-peer transport?
A: It can use either. By default, preference is given to UDP, but depending on the firewall(s) in between the peers connecting it may only be able to connect with TCP.
То есть UDP или (если UDP невозможно) TCP.
Или вы что-то другое хотели узнать?