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Network Game Research – Introduction and Counter-strike Analysis. Mark Claypool. Outline. Overview of Network Games Net Games Conference Research Issues Analysis Counter-strike Our Results. Why Study Games?. Rapidly increasing in popularity Forrester Research: 18 million on-line in 2001

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Presentation Transcript
  • Overview of Network Games
  • Net Games Conference
  • Research Issues
  • Analysis Counter-strike
  • Our Results
why study games
Why Study Games?
  • Rapidly increasing in popularity
    • Forrester Research: 18 million on-line in 2001
    • Consoles on-line
      • Playstation 2 on-line (9/2002)
      • Xbox Live (12/2002)
    • Cell phones
      • Doom port (Nokia)
  • Design networks to better accommodate traffic
game types
Game Types
  • First Person Shooters
    • Doom, Quake, Counter-strike, …
  • Massive Multi-Player Online Role Playing
    • Everquest, Earth and Beyond, …
  • Real-Time Strategy
    • Warcraft, Starcraft …
  • Other
    • Misc – not any genre above
      • Example: Diablo2, Racing, …
    • Non-networked
      • Example: Thief
    • Multiplayer, but relaxed real time
      • Example: Chess, Bridge
net games workshop on network and system support for games
Net-Games - Workshop on Network and System Support for Games
  • First was 2002 in Braunschweig, Germany
  • Second is in Redwood City, California
  • Sponsored by:
    • ACM
    • Electronic Arts
    • Microsoft
net games program committee
Net-Games Program Committee
  • Sugih Jamin, University of Michigan (Chair)
  • Mostafa Ammar, Georgia Institute of Technology
  • Grenville Armitage, Swinburne University of Technology
  • John Buchanan, Electronic Arts
  • Jon Crowcroft, University of Cambridge
  • Christophe Diot, Sprintlabs
  • Wu-chang Feng, Oregon Health and Science University
  • Carsten Griwodz, University of Oslo
  • Jim Kurose, UMass at Amherst
  • John Laird, University of Michigan
  • Brian Neil Levine, UMass at Amherst
  • Martin Mauve, University of Mannheim
  • Hiroyuki Morikawa, University of Tokyo
  • Dan Rubenstein, Columbia University
  • Srinivasan Seshan, Carnegie Mellon University
  • Wilson Yuen, City University of Hong Kong
  • Lars Wolf, TU Braunschweig
net games topics
Net-Games Topics
  • Multi-player game architectures and platforms
  • Prevention and detection of cheating
  • Games on mobile and resource-scarce devices
  • AI and techniques for latency hiding
  • Modeling, usage studies, and characterization
  • Enabling protocols for networked games
  • Systems support for authentication and accounting
  • Put research issues here
  • Understand the resource requirements of a popular on-line FPS (first-person shooter) game
why fps
Why FPS?
  • While there are other game types …
  • Gaming traffic dominated by first-person shooter genre (FPS) [McCreary00]
networked fps lineage
Networked FPS lineage



Unreal Tournament

Doom II


+ QuakeWorld variants

+ Team Fortress

+ Capture the Flag

Unreal Tournament 2003

+ America's Army: Operations

Quake II

+ Soldier of Fortune

+ Heretic II

Quake III Arena

+ Medal of Honor Allied Assault

+ Return to Castle Wolfenstein

+ Soldier of Fortune 2

+ Jedi Knight II


+ Counter-Strike

+ Day of Defeat

+ Urban Terror

+ Team Fortress Classic

+ Team Fortress 2

8 of top 10 games derived

from one of two lineages

Doom III

about the game
About the game...
  • Half-Life modification
  • Two squads of players competing in rounds lasting several minutes
  • Rounds played on maps that are rotated over time
  • Each server supports up to 32 players
about the game16
About the game...
  • Centralized server implementation
    • Clients update server with actions from players
    • Server maintains global information and determines game state
    • Server broadcasts results to each client
  • Sources of network traffic
    • Real-time action and coordinate information
    • Broadcast in-game text messaging
    • Broadcast in-game voice messaging
    • Customized spray images from players
    • Customized sounds and entire maps from server
the trace
The Trace
  • (
    • Dedicated 1.8GHz Pentium 4 Linux server
    • OC-3
    • 70,000+ unique players (WonIDs) over last 4 months
  • One week in duration 4/11 – 4/18
  • 500 million packets
  • 16,000+ sessions from 5800+ different players
variance time plot
Variance time plot

Less variance < 50ms

Remains to 30 min

Decreases above 30 min

(Normalized to base interval of 10ms)

digging deeper
Digging deeper
  • Periodic server bursts every 50ms
    • Game must support high interactivity
    • Game logic requires predictable updates to perform lag compensation

Interval size=10ms

Interval size=50ms

digging deeper23
Digging deeper
  • Low utilization every 30 minutes
    • Server configured to change maps every 30 minutes
    • Traffic evenly pegged otherwise....

Interval size=1sec

Interval size=30min

finding the source of predictability
Finding the source of predictability
  • Games must be fair across all mediums (i.e. 56kers)
    • Aggregate predictability due to “saturation of the narrowest last-mile link”
packet sizes
Packet sizes
  • Supporting narrow last-mile links with a high degree of interactivity requires small packets
    • Clients send small single updates
    • Servers aggregate and broadcast larger global updates
  • Routers, firewalls, etc. must be designed to handle large bursts at millisecond levels
    • Game requirements do not allow for loss or delay (lag)
    • Should not be provisioned assuming a large average packet size [Partridge98]
    • If there are buffers anywhere, they must...
      • Use ECN (no, doesn’t use TCP)
      • Be short (i.e. not have a bandwidth-delay product of buffering)
      • Employ an AQM that works with short queues
        • Rate-based not Queue-based
  • ISPs, game services
    • Must examine “lookup” utilization in addition to link utilization
    • Concentrated deployments of game servers may be problematic
      • Large server farms in a single co-lo
      • America's Army, UT2K3, Xbox
on going work
On-going work
  • Other pieces in the provisioning puzzle
    • Aggregate player populations
    • Geographic distributions of players over time (IP2Geo)
  • Impact on route and packet classification caching
  • Other FPS games
    • HL-based: Day of Defeat
    • UT-based: Unreal Tournament 2003, America's Army
    • Quake-based: Medal of Honor: Allied Assault
    • Results apply across other FPS games and corroborated by other studies
future work
Future work
  • Games as passive measurement infrastructure
    • Only widespread application with continuous in-band ping information being delivered (measurement for free)
    • “Ping times” of all clients broadcast to all other clients every 2-3 seconds
    • 20,000+ servers, millions of clients
  • Games as active measurement infrastructure
    • Thriving FPS mod community and tools
    • Server modifications [Armitage01]
  • Other game types
some net games research at wpi
Some Net-Games Research at WPI
  • Mark Claypool, David LaPoint, and Josh Winslow. “Network Analysis of Counter-strike and Starcraft”, In Proceedings of the 22nd IEEE International Performance, Computing, and Communications Conference (IPCCC), Phoenix, Arizona, USA, April 2003. Online at:
  • Compared FPS (Counter-strike) with RTS (Starcraft)
  • Smaller number of traces
  • Controlled set of users
our results
Our Results
  • Confirms packet sizes for Counter-strike
  • Starcraft results:
    • Packets smaller
    • Linear increase with number of players
  • Starcraft traffic much smoother (bandwidth usage) than Counter-strike
    • Counter-strike bursty during ‘fire-fights’
  • (PEDS talk later)