docker-compose/util/rtc_config.json

{
  "sdpSemantics": "unified-plan",
  "iceServers": [
    {
      "urls": "stun:stun.l.google.com:19302"
    },
    {
      "urls": "stun:stun1.l.google.com:19302"
    },
    {
      "urls": "stun:stun2.l.google.com:19302"
    },
    {
      "urls": "stun:stun3.l.google.com:19302"
    },
    {
      "urls": "stun:stun4.l.google.com:19302"
    }
  ]
}