Here’s some more info:
It may seem that sending and receiving files over the network would be a time consuming process with so much going on, but routing over the network is quite efficient using a Kademlia4-like distributed hash table (see below). With millions of nodes, it seems impossible to find a node closest to a certain ID. However, the amount of hops required to find a node closest to a particular address is O(log n), where n is the total number of nodes in the network. Put simply, in the absolute worst case scenario it will take 23 hops to locate a node with a particular ID in a network of 10 million nodes! Once located, they can communicate directly with each other.