Five or six years ago, I was stuck writing a network emulation layer for a PS2 game. I was told that all the classic behaviors of an internet connection had to be displayed; realistic loss characteristics, packet reordering, latency, rush-induced packet loss. Essentially, I was told to implement the internet in a couple weeks.  I suggested just bouncing all our game traffic off a remote echo server. When I was told that it was absolutely forbidden to send development traffic out over public wires, I simply created a server that everyone pointed their PS2 devkits at that would store every packet it received and send a doppleganger (full of an id for the original packet plus a bunch of random garbage to make it the same size) out to the echo servers I ran. When the doppleganger was received, I would pass the original packet on to its original destination.  Boom. Internet simulation with all the thorns.