The Effects of Loss and Latency on User Performance in Unreal Tournament 2003 Tom Beigbeder, Rory Coughlan, Corey Lusher, John Plunkett, Emmanuel Agu, Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, MA, USA

Aug 2004 NetGames'04, Portland, OG, USA2 Why Study Network Games and First Person Shooters? In 2003, despite economic downturn, games only industry to grow [ESA ] 43% of frequent game players play online [“Essential Facts”, ESA, 2004] First-Person Shooters a top selling genre –11.5% [“Essential Facts”, ESA, 2003]

Aug 2004 NetGames'04, Portland, OG, USA3 The Network and Network Games Can be a demanding application in terms of network requirements –Capacity? (Not usually) –Latency? (Sometimes … but when?) –Loss? (Unknown) But what about loss? –Retransmission adds to latency Knowing QoS constraints useful for –Building better network games –Building better networks to support games (QoS)

Aug 2004 NetGames'04, Portland, OG, USA4 Outline Introduction  Experiments  Analysis Conclusions

Aug 2004 NetGames'04, Portland, OG, USA5 Methodology Characterize FPS user interaction components Design maps that exercise each type of interaction Construct test environment for measuring the effects of latency and loss Conduct user studies Analyze the results (see Section 4).

Aug 2004 NetGames'04, Portland, OG, USA6 FPS User Interaction Components Movement –Simple (Moving in a straight line) –Complex (Running, jumping, turning…) Shooting Movement and Shooting

Aug 2004 NetGames'04, Portland, OG, USA7 Controlling Loss and Latency UT2003 Client-Server NIST Net router controls network characteristics to each client –Control loss [0%,6%] –Control and latency [0 ms, 400 ms]

Aug 2004 NetGames'04, Portland, OG, USA8 Outline Introduction  Experiments  Analysis –Application Level  –Network Level –User Level Conclusions

Aug 2004 NetGames'04, Portland, OG, USA9 Complex Movement Movement not affected by loss or latency Short-circuit relay

Aug 2004 NetGames'04, Portland, OG, USA10 Precision Shooting Precision shooting not affected by loss Precision shooting is affected by latency 75 ms may make a difference!

Aug 2004 NetGames'04, Portland, OG, USA11 Restricted Deathmatch Movement and shooting not affected by loss Movement and shooting affected by latency Less clearly so than shooting alone

Aug 2004 NetGames'04, Portland, OG, USA12 Full Deathmatch Movement and shooting not affected by loss Movement and shooting barely affected by latency

Aug 2004 NetGames'04, Portland, OG, USA13 Outline Introduction  Experiments  Analysis –Application Level  –Network Level  –User Level Conclusions

Aug 2004 NetGames'04, Portland, OG, USA14 Network Turbulence No visible effects of loss or latency Holds for packet sizes, intra packet times

Aug 2004 NetGames'04, Portland, OG, USA15 Outline Introduction  Experiments  Analysis –Application Level  –Network Level  –User Level  Conclusions

Aug 2004 NetGames'04, Portland, OG, USA16 User-Level Analysis 75 ms latency, users noticed sluggishness –True even for unrestricted tests 100 ms was noticeable, less enjoyable –Could be frustrating for precise shooting 0-3% loss rarely even noticed 3%+ loss sometimes noticed, but only because gun effects not always displayed

Aug 2004 NetGames'04, Portland, OG, USA17 Conclusion FPS games not affected by typical Internet loss –Keep loss under 3% –May not bode well for TCP fairness at higher bitrates Can be affected by latency –Keep latencies under 150 ms At the network level: –Small packets with low bitrate –Turbulence consistent over all network conditions

Aug 2004 NetGames'04, Portland, OG, USA18 Future Work Effects of variance in latency (jitter) User adaptation strategy Other?

The Effects of Loss and Latency on User Performance in Unreal Tournament 2003 Tom Beigbeder, Rory Coughlan, Corey Lusher, John Plunkett, Emmanuel Agu, Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, MA, USA