Incentive-build-Robustness激勵建立魯棒性課件

1、Incentives Build Robustness in BitTorrent?Analysis on Bit Torrent Client performanceBy Jimmy Wong1Incentives Build Robustness inAgendaIntroductionBitTorrent BasicsBit Tyrant: A strategic clientBit Thief: A free-riding clientOther Tricks of BT ClientReal World ExperimentsAvoiding of TricksConclusion2

2、AgendaIntroduction2IntroductionBitTorrent core incentiveUpload More, Download MoreProblem DefinitionI am a selfish userCan I gain without pay / pay less?3IntroductionBitTorrent core inBitTorrent BasicsStep 0 Publishing ContentCreate Torrent fileTracker URLSHA-1 Hash ChecksumAssign a TrackerDistribut

3、e Torrent to users through Web Site, Newsgroup or Forum4BitTorrent BasicsStep 0 PublBitTorrent BasicsStep 1 JoiningPeers get the TorrentConnect to TrackerLook for available peersDHT (Distributed Hash Table)Create connection with other peersStart with Others Optimistic UnchokingLook for better peersL

4、et other peers join the swarm5BitTorrent BasicsStep 1 JoinBitTorrent BasicsStep 2 to N-1 PipeliningExchange bitmap about which chunks are availablePay more, get moreTo build incentive for peers to uploadReciprocalRarest firstTo preserve File completeness among the swarmTo build up peers reputation6B

5、itTorrent BasicsStep 2 to N-1BitTorrent BasicsChokingSend data to only few good peersContribute data to youHave pieces that you wantsA resourceful peersIt will be nice if I can pay minimal cost to be un-choke!7BitTorrent BasicsChoking7BitTorrent BasicsOptimistic Un-chokingAllow new peers to get some

6、 pieces for exchangeAllow discovery of better exchanging partnersMost peers are so friendlyI can gain without contribute!8BitTorrent BasicsOptimistic UnBitTorrent BasicsEnding PhaseToward the end of downloadRequest for missing piecesSearch for available peers20-30 pieces left9BitTorrent BasicsEnding

7、 Phase9Bit Tyrant: A strategic clientIncentive100KB/s 15KB/s1% drop15KB/s 10KB/s40% drop About 1.9Mbps World Wide Bandwidth/news.ars/post/20070529-survey-average-broadband-speed-in-us-is-1-9mbps.htmlWhy do I still need to give u so much?10Bit Tyrant: A strategic clientBit Tyrant: A strategic clientR

8、esource ManagementBandwidth fixed# Conn x Speed = ConstantCurrent Official BT Protocol ( # of Leecher Even betterGain from both methodology17BitThief : A free-riding clienOther Tricks of BT ClientClient DiscriminationHigher priority for Similar ClientDelibrately choke other clientPretend to be Local

9、 NeighborFake tracker with wrong upload rateRetrieve from Seed Rapid Disconnect and ReconnectHope to gain from optimistic unchokingRemove from black-listMultiple Connection to the same clientFor high speed BBGain the most from the same client18Other Tricks of BT ClientClienExperiment with BT ClientT

10、esting EnvironmentAthlon 64 2800+1GB Ram120GB 7200 rpm HDDWindows XP SP2 w/ TCP Conn CrackBT SoftwareUtorrent / MainlineBit CometBit TryantiCable internet Connection19Experiment with BT ClientTestiExperiment with BT ClientGentoo AMD 64 Minimal ISO 54.4MB34 Seeders, 0 LeechersUbuntu 7.10 i386 Desktop

11、 ISO695MB928 Seeders / 78 LeechersNBA Match921MB120 Seeders, 714 Leechers20Experiment with BT ClientGentoExperiment with BT ClientGentooUploadTimeAvg SpeedKB/sConn PeerSeed/LeechBit Comet018:4050.6510/0uTorrent017:0155.6212/0Bit Tyrant015:0462.7516/021Experiment with BT ClientGentoExperiment with BT

12、 ClientUbuntuUploadTimeAvg SpeedKB/sConn PeerSeed/LeechBit Comet32MB15:20773.5775/70uTorrent112KB69:13171.3736/1Bit Tyrant100KB26:28448.1640/122Experiment with BT ClientUbuntExperiment with BT ClientNBAUploadTimeAvg SpeedKB/sConn PeerSeed/LeechBit Comet1070MB52:3229911/53uTorrent1035MB1:42:501527/29

13、Bit Tyrant540MB1:20:1019610/2223Experiment with BT ClientNBAUpExperiment with BT ClientBit Thief Achieve a high download rate (150KB/s) for Ubuntu and NBASuck at 25%24Experiment with BT ClientBit TAvoiding TricksTargetStop Fake InformationIdentify Free-ridingDifficultiesBit Torrent is so wide spread

14、Too many implementationsIncentive driven works again!Co-operative identify bad clientBlock bad peers, Share with good peers25Avoiding TricksTarget25Avoiding TricksSharing with PeersSearch for local optimal best peersSearch for potential bad peersBroadcast of bad peers (In a majority basics)It will f

15、ail if more than half of clients are in-honest26Avoiding TricksSharing with PeConclusionBT RobustnessMost peers are friendlyWays to CrackGain from cracking the protocolBit Tyrant: Download UploadBit Thief: Free RidingProposed SolutionDecentralized Client Solution27ConclusionBT Robustness27ReferenceIncentives Buil