ZeroTier is a way to connect devices over your own private network anywhere in the world. You do this by creating a network and then joining two or more devices to that network. You can use ZeroTier to play games, connect to remote business resources or even as a cloud backplane for your enterprise. Create your network.
ZeroTier uses a set of globally distributed root servers and network controllers to automatically negotiate P2P connections for your devices and provision your networks. You use Central to manage your networks. Here's a technical deep dive of the protocol.