The Effects of Latency on User Performance in Warcraft III Nathan Sheldon, Eric Gerard, Seth Borg, Mark Claypool, Emmanuel Agu Computer Science Department Worcester Polytechnic Institute Worcester, MA, USA

May 2003 NetGames'03, Redwood City, CA, USA2 Why Study Network Games? In 2000, U.S. economy grew by 7% while computer game industry grew by 15% 60% of Americans age 6+ play computer games 221+ million computer games sold in 2002 –2 games for every household in America “Top Ten Industry Facts”, Interactive Digital Software Association, May “Economic Impacts of the Demand for Interactive Entertainment Software”, Interactive Digital Software Association, 2001.

May 2003 NetGames'03, Redwood City, CA, USA3 Why Study Warcraft III? Top selling computer game genres –Strategy (27.4%) –Children’s (15.9%) –Shooter (11.5%) –Family Entertainment (9.6%) Warcraft III set sales record –Fastest to sell 1 million copies “Warcraft III - Shatters Sales Records Worldwide...”, Blizzard Press Release, October 2002 “Top Ten Industry Facts”, Interactive Digital Software Association, May 2003.

May 2003 NetGames'03, Redwood City, CA, USA4 Network Games and Latency Latency degrades performance of interactive applications –Web-browsing – seconds –Audioconference – 100’s of milliseconds –First Person Shooters (FPS) – 100’s of milliseconds Real-Time Strategy (RTS)? Knowing effects of latency useful for –Building better network games –Building better networks to support games (QoS)  Effects of Latency on Warcraft III (RTS)

May 2003 NetGames'03, Redwood City, CA, USA5 Outline Introduction  Experiments  Analysis Conclusions

May 2003 NetGames'03, Redwood City, CA, USA6 Warcraft III Overview RTS User Interaction Components: Exploration Building Combat

May 2003 NetGames'03, Redwood City, CA, USA7 Exploration Map Performance? Time (to reach end)

May 2003 NetGames'03, Redwood City, CA, USA8 Building Map Performance? Time (to build tech- nology tree)

May 2003 NetGames'03, Redwood City, CA, USA9 Combat Map Performance? Games Won Unit Scores

May 2003 NetGames'03, Redwood City, CA, USA10 Controlling Latency Warcraft III uses client-server –Set computer B as server (also a client) –Set computer C or D as client NIST Net on computer A –Induce latency [0 ms to 3500 ms]

May 2003 NetGames'03, Redwood City, CA, USA11 Outline Introduction  Experiments  Analysis –Application Level  –Network Level –User Level Conclusions

May 2003 NetGames'03, Redwood City, CA, USA12 Building and Latency

May 2003 NetGames'03, Redwood City, CA, USA13 Exploration and Latency

May 2003 NetGames'03, Redwood City, CA, USA14 Combat and Latency (1)

May 2003 NetGames'03, Redwood City, CA, USA15 Combat and Latency (2)

May 2003 NetGames'03, Redwood City, CA, USA16 Outline Introduction  Experiments  Analysis –Application Level  –Network Level  –User Level Conclusions

May 2003 NetGames'03, Redwood City, CA, USA17 Bandwidth 3.8 Kbps 4.0 Kbps 6.8 Kbps

May 2003 NetGames'03, Redwood City, CA, USA18 Inter-Packet Times

May 2003 NetGames'03, Redwood City, CA, USA19 Payload Distributions

May 2003 NetGames'03, Redwood City, CA, USA20 Bandwidth and Latency Battle.net games had ~100 ms latency Trace combat maps with induced latency

May 2003 NetGames'03, Redwood City, CA, USA21 Payload Distributions and Latency

May 2003 NetGames'03, Redwood City, CA, USA22 Commands and Latency Pilot studies suggest 6 bytes of overhead per command Remove 6 bytes from each packet payload Add up remaining command payloads

May 2003 NetGames'03, Redwood City, CA, USA23 Outline Introduction  Experiments  Analysis –Application Level  –Network Level  –User Level  Conclusions

May 2003 NetGames'03, Redwood City, CA, USA24 User-Level Analysis ms latency, users could easily adjust 800+ ms, game appeared erratic –Degradation in gaming experience ms degradation depended upon –User More skilled were more sensitive –Strategy Micro managers were more sensitive Combat managers were more sensitive

May 2003 NetGames'03, Redwood City, CA, USA25 Conclusions Typical Internet latencies do not significantly affect user performance in Warcraft III –Some effect on exploration –No statistical effect on building or combat RTS game play emphasizes “strategy” (which takes 10s of seconds or minutes), not “real-time” RTS games less sensitive to latency than are FPS –RTS in QoS class similar to that of Web browsing At the network level: –Small packets with low bandwidth –Command aggregation at higher latencies

May 2003 NetGames'03, Redwood City, CA, USA26 Future Work Effects of latency on user strategies Other RTS games –Age of Empires –Command and Conquer Effects of latency on other genres –First Person Shooter –Role Playing Game Effects of loss

The Effects of Latency on User Performance in Warcraft III Nathan Sheldon, Eric Gerard, Seth Borg, Mark Claypool, Emmanuel Agu Computer Science Department Worcester Polytechnic Institute Worcester, MA, USA