Scalable AOI-cast for Peer-to-Peer Networked Virtual Environments

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Jehn-Ruey Jiang, Yu-Li Huang, and Shun-Yun Hu CSIE, National Central University, Taiwan 2008/06/20. Scalable AOI-cast for Peer-to-Peer Networked Virtual Environments. Networked Virtual Environments (NVEs). NVEs such as MMOGs are growing quickly Multi-billion dollar industry - PowerPoint PPT Presentation


  • Scalable AOI-cast for Peer-to-Peer Networked Virtual Environments

    Jehn-Ruey Jiang, Yu-Li Huang, and Shun-Yun Hu

    CSIE, National Central University, Taiwan


  • Networked Virtual Environments (NVEs)NVEs such as MMOGs are growing quickly Multi-billion dollar industry10 million subscribers for World of Warcraft600,000 concurrent users, but 3,000 per world

    Can we scale to millions in the same world?

  • The basic problemClient-server: resources limited by provisioningResource limit[Funkhouser95]

  • An intuitive solutionPeer-to-Peer: resources grow with demandResource limit [Keller & Simon 2003]

  • Key to scalabilityUsers have limited visibility called Area of Interest (AOI)Bounded resource usage achievable by exchanging messages only with AOI neighbors (i.e., an AOI-cast)Area of Interest

  • If you talk with your AOI Neighbors directlygames can be builtBut how to discover new neighbors?

  • Related Work: VON [hu et al. 2006]1)Positions sent to all neighborsBoundary neighbors check for new neighbors2)Connect to new nodes upon notification Disconnect any non-overlapped neighborsBoundary neighborsNew neighborsNon-overlapped neighbors

  • Related Work: VON-forwarding [chen et al. 2007]Only connect with 1-hop neighborsAOI-cast via forwardingAggregation & compression utilizable

    Problem: redundant message transmission

  • Related Work: APOLO [lee et al.2006]Each node keeps 4 out-direction links onlyNon-redundant transmission

    Problem: Inefficient transmission path

  • VoroCastGoals:Keep the simplicity & advantage of forwardingDeliver messages without redundancyConstruct spanning trees in a distributed manner

    Observation:Growing a tree from root easily creates redundancyGrowing a tree from children avoids redundancy


  • User density issueHigh user density in AOI can still be a problem

    To improve AOI scalability when user density is high, consistency can be traded for less bandwidth

    Those further away need not receive updates all the time

  • FiboCastMessage frequency to distant nodes should be adjustable

    Add an increasingly longer time-to-live (TTL) for each round of messages maximum hop count sequence that increases (e.g. a Fibonacci sequence such as {0, 1, 1, 2, 3, 5, 8}Minimum 2-hop forwarding (for VoroCast to work)

  • Example routing lengthFor a sequence up to 8, we save 24 updates


  • Simulation evaluation

    Map:1000 x 1000 unitsNodes: 100 ~ 1000 (in increments of 100)AOI radius: 200 unitsTime-steps:3000 (100ms / step)Speed:5 units / step (random waypoint pattern)FiboCast:{0, 1, 1, 2, 3, 5, 8} sequence

    Data is compressed by zlib

  • Bandwidth consumption

  • Neighborship consistency

  • ConclusionA simple method of constructing spanning trees distributively that allows non-redundant AOI-cast

    AOI scalability is improved by reducing bandwidth use

    Aggregation and compression further save bandwidth

  • Backup slides

  • Why 2-hop neighbors?

  • Drift distance

  • Procedure (JOIN)1)Joining node sends coordinates to any existing nodeJoin request is forwarded to acceptor2)Acceptor sends back its own neighbor listjoining node connects with other nodes on the listAcceptors regionJoining node

  • Procedure (LEAVE)1)Simply disconnect2)Others then update their Voronoinew B.N. is discovered via existing B.N.

    Leaving node (also a B.N.)New boundary neighbor



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