peer to peer support for massively multiplayer games
Download
Skip this Video
Download Presentation
Peer-to-Peer Support for Massively Multiplayer Games

Loading in 2 Seconds...

play fullscreen
1 / 43

Peer-to-Peer Support for Massively Multiplayer Games - PowerPoint PPT Presentation


  • 117 Views
  • Uploaded on

Peer-to-Peer Support for Massively Multiplayer Games. Bjorn Knutsson, Honghui Lu, Wei Xu, Bryan Hopkins. Presented by Mohammed Alam (Shahed). Outline. Introduction Overview of MMG Peer-to-Peer Infrastructure Distributed Game Design Game on P2P overlay Experimental Results

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Peer-to-Peer Support for Massively Multiplayer Games' - mahina


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
peer to peer support for massively multiplayer games

Peer-to-Peer Support for Massively Multiplayer Games

Bjorn Knutsson, Honghui Lu, Wei Xu, Bryan Hopkins

Presented by

Mohammed Alam (Shahed)

outline
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
outline1
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
introduction
Introduction
  • Proposes use of P2P overlays to support Massively multiplayer games (MMG)
  • Primary contribution of paper:
    • Architectural (P2P for MMG)
    • Evaluative
introduction1
Introduction

MMG GAME

SCRIBE

(Multicast support)

PASTRY

(P2P overlay)

introduction2
Introduction
  • Players contribute memory, CPU cycles and bandwidth for shared game state
  • Three potential problems:
    • Performance
    • Availability
    • security
outline2
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
overview of mmg
Overview of MMG
  • Thousands of players co-exist in same game world
  • Most MMG’s are role playing games (RPG) or real-time strategy(RTS) or hybrids
  • Examples: Everquest, Ultima online, Sims online
overview of mmg1
Overview of MMG
  • GAME STATES

World made up of

    • immutable landscape information (terrain)
    • Characters controlled by players
    • Mutable objects (food, tools, weapons)
    • Non-player characters (NPCs) controlled by automated algorithms
overview of mmg2
Overview of MMG
  • GAME STATES (contd..)
    • Game world divided into connected regions
    • Regions on different servers
      • Regions further divided to keep data in memory small
overview of mmg3
Overview of MMG
  • EXISTING SYSTEM SUPPORT
    • Client-server architecture
      • Server responsible for
        • Maintain & disseminate game state
        • Account management & authentication
      • Scalability achieved by
        • Dedicated servers
        • Clustering servers
          • LAN or computing grid
overview of mmg4
Overview of MMG
  • Latency
    • Varies
    • Guiding ‘avatars’ tolerates more latency
    • First person shooter games (180 millisecond latency max)
    • Real time strategy (several seconds)
outline3
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
peer to peer infrastructure
Peer-to-Peer Infrastructure

MMG GAME

SCRIBE

(Multicast support)

PASTRY

(P2P overlay)

outline4
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
distributed game design1
Distributed Game Design
  • Persistent user state is centralized
    • Example: payment information, character
  • Allows central server to delegate bandwidth and process intensive game state to peers
distributed game design2
Distributed Game Design
  • Game design based on fact that:
    • Players have limited movement speed
    • Limited sensing capability
    • Hence data shows temporal and spatial localities
    • Use Interest Management
      • Limit amount of state player has access to
distributed game design3
Distributed Game Design
  • Players in same region form interest group
  • State updates relevant to group disseminated only within group
  • Player changes group when going from region to region
distributed game design4
Distributed Game Design
  • GAME STATE CONSISTENCY
    • Must be consistent among players in a region
    • Basic approach: employ coordinators to resolve update conflicts
    • Split game state management into three classes to handle update conflicts:
      • Player state
      • Object state
      • The Map
distributed game design5
Distributed Game Design
  • Player state
    • Single writer multiple reader
    • Player-player interaction effects only the 2 players involved
    • Position change is most common event
      • Use best effort multicast to players in same region
      • Use dead reckoning to handle loss or delay
distributed game design6
Distributed Game Design
  • Object state
    • Use coordinator-based mechanism for shared objects
    • Each object assigned a coordinator
    • Coordinator resolves conflicting updates and keeps current value
outline5
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
game on p2p overlay
Game on P2P overlay
  • Map game states to players
    • Group players & objects by region
    • Map regions to peers using pastry Key
    • Each region is assigned ID
    • Live Node with closest ID becomes coordinator
    • Random Mapping reduces chance of coordinator becoming member of region (reduces cheating)
    • Currently all objects in region coordinated by one Node
    • Could assign coordinator for each object
game on p2p overlay1
Game on P2P overlay
  • Shared state replication
    • Lightweight primary- backup to handle failures
    • Failure detected using regular game events
    • Dynamically replicate coordinator when failure detected
    • Keep at least one replica at all times
    • Uses property of P2P (route message with key K to node ID, N , closest to K)
game on p2p overlay2
Game on P2P overlay
  • Shared state replication (contd..)
    • The replica kept at M which is the next closest to message or object K
    • If new node added which is closer to message K than coordinator
      • Forwards to coordinator
      • Updates itself
      • Takes over as coordinator
game on p2p overlay3
Game on P2P overlay
  • Catastrophic failure
    • Both coordinator and replica dead
    • Problem solved by cached information from nodes interested in area
outline6
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
experimental results
Experimental Results
  • Prototype Implementation of “SimMud”
  • Used FreePastry (open source)
  • Maximum simulation size constrained by memory to 4000 virtual nodes
  • Players eat and fight every 20 seconds
  • Remain in a region for 40 seconds
  • Position updates every 150 millisec by multicast
experimental results1
Experimental Results
  • Base Results
    • No players join or leave
    • 300 seconds of game play
    • Average 10 players per region
    • Link between nodes have random delay of 3-100 ms to simulate network delay
experimental results base results1
Experimental Results(Base results)
  • 1000 to 4000 players with 100 to 400 regions
  • Each node receives 50 –120 messages
  • 70 update messages per second
    • 10 players * 7 position updates
  • Unicast and multicast message take around 6 hops
experimental results2
Experimental Results
  • Breakdown of type of messages
    • 99% messages are position updates
    • Region changes take most bandwidth
    • Message rate of object updates higher than player-player updates
      • Object updates multicast to region
      • Object update sent to replica
      • Player player interaction effects only players
experimental results3
Experimental Results
  • Effect of Population Growth
    • As long as average density remains same, population growth does not make difference
  • Effect of Population Density
    • Ran with 1000 players , 25 regions
    • Position updates increases linearly per node
    • Non – uniform player distribution hurts performance
experimental results4
Experimental Results
  • Three ways to deal with population density problem
    • Allow max number of players in region
    • Different regions have different size
    • System dynamically repartitions regions with increasing players
experimental results5
Experimental Results
  • Effect of message aggregation
    • Since updates are multicast, aggregate them at root
    • Position update aggregated from all players before transmit
    • Cuts bandwidth requirement by half
    • Nodes receive less messages
experimental results8
Experimental Results
  • Effect of network dynamics
    • Nodes join and depart at regular intervals
    • Simulate one random node join and depart per second
    • Per-node failure rate of 0.06 per minute
    • Average session length of 16.7 minutes (close to 18 minutes for half life)
    • Average message rate increased from 24.12 to 24.52
    • Catastrophic failure every 20 hours
outline7
Outline
  • Introduction
  • Overview of MMG
  • Peer-to-Peer Infrastructure
  • Distributed Game Design
  • Game on P2P overlay
  • Experimental Results
  • Future Work and Discussion
future work
Future Work
  • Assumes uniform latency for now
  • Testing games with more states and on global distributed network platforms
  • Stop cheating by detection
discussion
Discussion
  • Assigning random coordinators could hurt in P2P (modem vs high-speed)
  • How close can the results obtained in simulation on one machine work in real
  • Given range of 7.2kB/sec – 22.34 KB/sec in easy game. What about games with more states
  • How would aggregating messages be bad?
    • In their case waits for all messages to come before sending? Latency issues?
ad