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Long network latency negatively impacts the performance of online games, and thus mechanisms are needed to mitigate its effects in order to provide a high-quality gaming experience. In this paper, we propose an indirect relay system (IRS) to forward game-state updates over detour paths in order to reduce the round-trip time (RTT) among players. We first collect extensive traces for RTTs among actual players in online games. We then analyze these traces to quantify the potential performance gain of the detour routing. Our analysis reveals that substantial reduction in the RTTs is possible. For example, our results indicate that more than 40% of players can observe at least 100 ms of RTT reduction by routing game-state updates through 1-hop detour paths. Because of the reduction in RTTs, players can join more gaming sessions that were not available to them due to long RTTs of the direct paths. Most importantly, we design and implement a complete IRS system for online games. To the best of our knowledge, this is the first system that directly reduces RTTs among players in online games, while previous works in the literature mitigate the long RTT issue by either hiding it from players or preventing players with high RTTs from being in the same game session. We implement the proposed IRS system and deploy it on 500 PlanetLab nodes. The results from real experiments show that the IRS system improves the online gaming quality from several aspects, while incurring negligible network and processing overheads. In particular, we observe that, with the proposed IRS system, more than 80% of game sessions achieve 100 ms or higher RTT reduction.
Date of Publication: Aug. 2011