http://i3xi5qxvbrngh3g6o7czwjfxwjzigook7zxzjmgwg5b7xnjcn5hzciad.onion/proposals/348-udp-app-support.html
We require support for peer-to-peer UDP transfer without additional relaying, in apps that use ICE ( RFC8445 ) or similar connection establishment techniques.
Video calls between two Tor users should transit directly between two exit nodes.
This requires that allocated UDP ports can each communicate with multiple peers: endpoint-independent mapping as described by RFC4787.