Post-game estimation of game client RTT and hop count distributions

In first person shooter (FPS) games the round trip time (RTT) (delay, or 'lag') between a client and server is an important criterion for players when deciding which server to join. Estimating the actual importance of this criterion can be challenging. Most game servers do not accurately log the RTT of either connected clients or potential clients (ones who only probed the server). Traffic traces also provide only IP addresses of hosts communicating with the game server. In this paper we propose a simple, active method of estimating the RTT between server and client when armed only with each client's IP address. For rough approximations this scheme works days or weeks after client IP addresses were collected. As jitter tends to be influenced by router hops we also discuss how to estimate the probable hop count between server and client. We illustrate our approach using data gathered from a Wolfenstein Enemy Territory server operating in Melbourne, Australia. This example shows our approach enabling after-the-fact comparisons between the RTT and hop-count distributions of clients who probe a server versus clients who actually join a server and play.