While TURN is more robust than STUN in that it assists in traversal of more types of NATs, a TURN communication relays the entire communication through the server requiring far more server bandwidth than the STUN protocol, which typically only resolves the public facing IP address and relays the information to client and peer for them to use in direct communication. For this reason, the ICE protocol mandates STUN usage as a first resort, and TURN usage only when dealing with symmetric NATs or other situations where STUN cannot be used.