Online Games: Networking and Data Management

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Online GamesNetworking and Data Management
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Why do we network games?

• Playing by yourself is NO FUN!
• Adds social dimension to gaming
• But we have the complexities of distributed
  computing
• From a systems perspective
• How do we cope with these physical restrictions,
  while developing and running our game?

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Taxonomy
MMOGs Everquest, WoW
Degree of distribution
Turn-based Civ, Poker
Cooperative Halo, Battlefield 2
Twitch games Doom, etc.
Degree of interaction
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Lecture Outline

• LAN Internet play
• Latency
• Scalability
• Data management
• Tools
• Data-driven games

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Networked Game Data
Shared game world
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LAN Game Anatomy
Client
Server
Snapshot
Physics
Physics
AI
State
State
AI
UI

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The Duel
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The Duel
Server
time
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The Duel
Server
work
time
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The Duel
Server
work
time
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The Duel
Server
work
time
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Massively Multiplayer

• Network latency
• E.g. Current TCP/UDP
• NYC gt Seoul, Korea 150ms one-way
• At best speed of light constraint between
  players
• NYC gt Seoul 11000km/c 36ms
• Scalability issues
• Load balancing
• Data dissemination

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Network Latency

• Two components
• Last-link latency
• Server-server latency
• Last-link latency is hard to cope with
• Cable-modem gt exchange
• But no other route

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Dead Reckoning

• Predict to overcome latency!
• Prediction models
• Newtonian (linear)
• Not everything can be predicted
• Developer must think about consequences of failed
  predictions

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The Duel Revisited
Server
time
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The Duel Revisited
Server
predict
time
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Dead Reckoning (in more depth)

• Videos

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Data Consistency

• Client cache
• Static data consistency is easy.
• Dynamic consistency is harder
• Ownership issues
• Interest management

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Fairness Models

• Who is right, the shooter or the victim?
• What are other scoring models?
• E.g. everything hurts a lot at first

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Growing the System

• Recap the LAN setup
• Suppose we want 1000 players

Client
Server
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Scalability Load Balancing

• Zone partitioning
• Each server may be distributed as a cluster
• Server placement and geographical partitioning
  helps

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Scalability Data Dissemination

• All about saving bandwidth
• Tree network between zones
• i.e. pub/sub system
• Zone transitions
• Artificial impediment to gameplay
• Content-based routing and profiles

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Data Dissemination Hotplugging

• Open, dynamic systems
• Recently attempted by
• WoW
• Star Wars Galaxies
• Should be seamless!

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PlanetLab
645 nodes, 305 sites
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Data Management

• What kinds of data are used to build and run
  games?
• Content
• Visual models, animations, artwork
• Audio effects, speech, languages
• Contextual plot, missions
• Game logic
• Player profiles, inventories, etc.
• NPC AI state.
• Transient
• Chat, VoIP

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Data Management Tools

• Expressive, declarative approach
• High-level triggers and rules
• Distribution transparency
• Clear-cut specification of game behaviour
• Modular frontend and backend extensibility
• Automated resource optimization
• Scalable
• Adaptive
• Tolerant to failures

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Dataflow Programming

• Flow-based representation of program
• Based on events and triggers
• Game logic defined as triggers
• E.g collision induced events
• Gameplay from queries over events
• Supports roles
• E.g. tell me when there are 5 players near my
  flag

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Dataflow Programming

• Borealis Demo
• Other distributed middleware kits
• Demonware, Quazcal, ReplicaNet
• Opensource MASSIV, Worldforge

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Dataflow Programming

• What are good primitives for games?
• E.g., collision detection, path planning, etc.
• Class-specific primitives?
• E.g buy/sell items
• Come up with a high-level game template

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Data-driven Gaming

• Lets use the data out there!
• Content, plot and script generation.
• Game embedding
• Splinter Cell, Battlefield 2
• The Sims
• Civilization
• Alternate reality gaming

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Mobile Gaming

• Sensors/actuators
• Power concerns
• Wireless connectivity
• Connection range
• Interruptions
• Data mules
• GPS
• Camera phones
• Google Maps

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Data-driven Gaming
classify
Pirate raid

Coastal map
Mission objective
Data sources
Game entities
Game level
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Data-driven Gaming Pipeline

• Acquisition
• News feeds (RSS/Atom)
• Integration
• Duplicate elimination
• Event classification
• Morphing
• Introducing dissimilarities
• Consistency checking
• Deployment

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Conclusions

• Latency causes inconsistencies in any distributed
  game.
• Scalable infrastructures to sustain game growth
• Data management tools, describing a high-level
  game representation
• Sources of game data

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Thanks!

• yna_at_cs