多nat情况下, server-reflexive candidate是最靠近TURN的nat
“
When there are multiple NATs between the agent and the TURN server, the TURN request will create a binding on each NAT, but only the outermost server-reflexive candidate (the one nearest the TURN server) will be discovered by the agent.
”
ref: https://www.rfc-editor.org/rfc/rfc8445#section-2.1