MCCA : A Communication Architecture for Online Multiplayer Games

1. MCCA : A Communication Architecture for Online Multiplayer Games Armin Bahramshahry

2. Outline • Background • Problem • Solution • Evaluation • Summary

3. Video Games Simulate a virtual world, and represent players as avatarswith cool gunsand swords

4. Online Multiplayer Games • Run multiplegame instances and desire to convergeto the same game state Internet

5. Problem • Traditional Challenges > game traffic • Limited upload capacity & communication delay • New Challenges >heterogeneous traffic Message Event Queues Player Action Internet Message Queues Event

6. Background Game Area-of-Interest (AOI) Predictive Contract Mechanism (PCM) Game Updates Updates Network Services Network Quality of Service (e.g., OverQoS) Game Game Updates

7. Approach Game VoIP File • Simplify development • Key Idea #1: Divide and Conquer • Efficient use of network resources • Key Idea #2: Cooperate with the Game • Support for new game level optimizations • Enable game adaptation to network conditions Game Optimizations ? Requirements MCCA Services Services & Information Network Services Game Update VoIP Traffic File Transfer Game Network Services

8. Key Ideas KEY #1: Divide and Conquer • Differentiated Services • Class Definition • Priority • Order & reliability • Loss rate • Latency requirements • Bit-rate throttling Game VoIP File Game Optimizations Requirements ? MCCA Differentiated Services Network Services

9. Key Ideas (cont.) KEY #2: Cooperate with the Game • Network Condition Reports (local) • Observed network conditions: Loss, latency, jitter • Group Communication Policy • Quality Estimation • Distributed Quality Aggregation(global) Game VoIP File Game Quality Estimation Optimizations Requirements Requirements & Quality Quality ? Reports MCCA Differentiated Services Message Forwarding Network Services

10. (α)latency - 100ms for Quake III Max Quality Quality Estimation Game Message Quality • Perceived QoS is Class Dependent • Game • Estimate game update quality • Based on observed loss and delay • VoIP • Based on télécommunication standard (E-model) • File Transfer • Transfer rate (β) latency – 200ms for Quake III No Quality Latency Game VoIP File Game Optimizations Quality Estimation Requirements & Quality Quality Reports MCCA Differentiated Services Message Forwarding Network Services

11. Optimizations • Optimistic Game • Uses negative acknowledgments (i.e., N-consecutive message losses) • Avoids large updates and wasteful acknowledgments • Adaptive Game Update Interval • Dynamically sets the game update interval (based on the estimated observed quality) • Reduces network traffic due to game updates • VoIP Optimization • Disables VoIP at low qualities • Avoids useless VoIP traffic Game VoIP File Game Optimizations Quality Estimation Requirements & Quality Quality Reports MCCA Differentiated Services Message Forwarding Network Services

12. Evaluation Methodology Game VoIP File Game Optimizations Quality Estimation Requirements & Quality Quality Reports MCCA Differentiated Services Message Forwarding Network Services Real Network Network Emulator Network Simulator

13. Workload Generators • Game Update Generator • First person shooting game, Quake III (based on the model by Bharambe et al., SIGCOMM’08) • Two-frame delta encoding • 20 game updates per second • VoIP Traffic • On/Off Markov process(based on the model by Padungkrit et al.) • 50 VoIP messages per second • File Transfer • At uniformly distributed intervals Game VoIP File Game Optimizations Quality Estimation Requirements & Quality Quality Reports MCCA Differentiated Services Message Forwarding Network Simulator

14. Network Simulator • Operates at the message level • Provides point-to-point communication • Does not simulate cross network traffic • Upload capacity << Network core (Bharambe et al.) • Network Simulator Validation: • Compare to a packet-level network emulator Game VoIP File Game Optimizations Quality Estimation Requirements & Quality Quality Reports MCCA Differentiated Services Message Forwarding Network Simulator

15. Evaluation • Workload Combinations • Game Level Optimizations • Class Definitions • Window-size • Redundancy level and redundancy interval • Forwarding policy • Workload Definitions • Real-Time Changes in: • Number of players • Upload capacity • Deployment Environment • …

16. Comparing Effectiveness of Optimizations New game-level optimizations!

17. Effectiveness of Classification & Optimizations Efficient use of network resources & new game-level optimization!

18. Adaptivenessto Changing Conditions Game can adapt!

19. Summary of Evaluation Results • Better gaming experience using: • Prioritization • Classification • Targeted QoS • Efficient group communication • Distributed quality aggregation enables game adaptation to network conditions • Lower quality variability among players

20. Contributions • Demonstrated the benefits of: • Differentiated services • Cooperation with the game • Prototyped a generic communication layer for online games (MCCA) • Experimental evaluation of MCCA at the communication layer to improve player’s experience.

21. Summary • Outcome: • Paper submission to NetGames 2009 • Network Engineer @ United Front Games Other Publications: • “vanDisk: An Exploration in Peer-To-Peer Collaborative Back-up Storage”, Amir Javidan, Tony Angerilli, Armin Bahramshahry, Guy Lemieux, Roman Lisagor, Matei Ripeanu, 20th IEEE Canadian Conference on Electrical and Computer Engineering, Vancouver, BC, April 2007. • “A High-Performance GridFTP Server at Desktop Cost”, Samer Al-Kiswany, Armin Bahramshahry, HesamGhasemi, Matei Ripeanu, Sudharshan S. Vazhkudai, poster, SC2007, Reno, NV, November 2007. Game VoIP File Game Optimizations Quality Estimation Requirements & Quality Quality Reports MCCA Differentiated Services Message Forwarding Network Services