A TURN server provides a standard way to relay media on behalf of users who are stuck on a NAT network. The Interactive Connectivity Establishment (ICE) protocol uses the TURN server to help explore network topology and give immediate feedback if the call is not possible, eliminating the menace of ghost calls.

Several TURN servers are now available in convenient Linux packages, see Chapter 10, ICE/STUN/TURN server installation for details about selecting and installing one.