IntroductionOverview of BitTorrentOverview of BitTorrentTerminologyIssues to Be AddressedModelA Simple Fluid ModelSteady-State PerformanceSteady-State PerformanceEffectiveness of File SharingEffectiveness of File SharingEffectiveness of File SharingStabilityCharacterizing VariabilityCharacterizing VariabilitySimulation ResultSimulation ResultSimulation ResultSimulation ResultExperimental ResultExperimental ResultConclusionsModeling and PerformanceAnalysis of BitTorrent-LikePeer-to-Peer NetworksDongyu Qiu, R. SrikantDepartment of Electrical and Computer EngineeringandCoordinated Science LabUniversity of IllinoisCSL, UIUC – p.1/23IntroductionPeer-to-peer networks:Peers participate in an application level overlaynetwork and operate as both servers and clients.Scalable: the service burden is distributed to allparticipating peers.Applications: File sharing, distributed directory service,web cache, storage, and grid computation etc.P2P file sharing: Kazza, Gnuttella, eDonkey/Overnet,BitTorrent.In some segments of the Internet, P2P traffic accountsfor 40% of the Internet traffic.CSL, UIUC – p.2/23Overview of BitTorrentSeed is a server that has the entire fileFile stored in many pieces of 256 KB eachA new peer starts downloading some pieces from theseedIf there are many peers, each peer will have differentparts of the fileKey point: Peers download from each otherCSL, UIUC – p.3/23Overview of BitTorrentSeed is a server that has the entire fileFile stored in many pieces of 256 KB eachA new peer starts downloading some pieces from theseedIf there are many peers, each peer will have differentparts of the fileKey point: Peers download from each otherCSL, UIUC – p.3/23Overview of BitTorrentSeed is a server that has the entire fileFile stored in many pieces of 256 KB eachA new peer starts downloading some pieces from theseedIf there are many peers, each peer will have differentparts of the fileKey point: Peers download from each otherCSL, UIUC – p.3/23Overview of BitTorrentSeed is a server that has the entire fileFile stored in many pieces of 256 KB eachA new peer starts downloading some pieces from theseedIf there are many peers, each peer will have differentparts of the fileKey point: Peers download from each otherCSL, UIUC – p.3/23Overview of BitTorrentSeed is a server that has the entire fileFile stored in many pieces of 256 KB eachA new peer starts downloading some pieces from theseedIf there are many peers, each peer will have differentparts of the fileKey point: Peers download from each otherCSL, UIUC – p.3/23Overview of BitTorrent:HE 6HUYHU7UDFNHU3HHU 3HHU 3HHU 3HHU 3HHU Peer 5 joins thenetworkdownloads a.torrent fileconnects to thetrackerthe tracker returnspeer informationconnects to otherpeers and beginsdownloadingCSL, UIUC – p.4/23Overview of BitTorrent:HE 6HUYHU7UDFNHU3HHU 3HHU 3HHU 3HHU 3HHU WRUUHQW ILOHPeer 5 joins thenetworkdownloads a.torrent fileconnects to thetrackerthe tracker returnspeer informationconnects to otherpeers and beginsdownloadingCSL, UIUC – p.4/23Overview of BitTorrent:HE 6HUYHU7UDFNHU3HHU 3HHU 3HHU 3HHU 3HHU Peer 5 joins thenetworkdownloads a.torrent fileconnects to thetrackerthe tracker returnspeer informationconnects to otherpeers and beginsdownloadingCSL, UIUC – p.4/23Overview of BitTorrent:HE 6HUYHU7UDFNHU3HHU 3HHU 3HHU 3HHU 3HHU Peer 5 joins thenetworkdownloads a.torrent fileconnects to thetrackerthe tracker returnspeer informationconnects to otherpeers and beginsdownloadingCSL, UIUC – p.4/23Overview of BitTorrent:HE 6HUYHU7UDFNHU3HHU 3HHU 3HHU 3HHU 3HHU Peer 5 joins thenetworkdownloads a.torrent fileconnects to thetrackerthe tracker returnspeer informationconnects to otherpeers and beginsdownloadingCSL, UIUC – p.4/23TerminologyA peer which has the entire file is called a seedA peer that is not a seed is called a downloaderA downloader becomes a seed once it has the entire fileEach peer uploads to five other peers who give it thebest download ratesEvery 30 seconds, drops its connection to peer with thesmallest download rate and picks a new one at randomCSL, UIUC – p.5/23TerminologyA peer which has the entire file is called a seedA peer that is not a seed is called a downloaderA downloader becomes a seed once it has the entire fileEach peer uploads to five other peers who give it thebest download ratesEvery 30 seconds, drops its connection to peer with thesmallest download rate and picks a new one at randomCSL, UIUC – p.5/23TerminologyA peer which has the entire file is called a seedA peer that is not a seed is called a downloaderA downloader becomes a seed once it has the entire fileEach peer uploads to five other peers who give it thebest download ratesEvery 30 seconds, drops its connection to peer with thesmallest download rate and picks a new one at randomCSL, UIUC – p.5/23TerminologyA peer which has the entire file is called a seedA peer that is not a seed is called a downloaderA downloader becomes a seed once it has the entire fileEach peer uploads to five other peers who give it thebest download ratesEvery 30 seconds, drops its connection to peer with thesmallest download rate and picks a new one at randomCSL, UIUC – p.5/23TerminologyA peer which has the entire file is called a seedA peer that is not a seed is called a downloaderA downloader becomes a seed once it has the entire fileEach peer uploads to five other peers who give it thebest download ratesEvery 30 seconds, drops its connection to peer with thesmallest download rate and picks a new one at randomCSL, UIUC – p.5/23Issues to Be AddressedPeer EvolutionScalabilityFile Sharing EfficiencyIncentive Mechanisms and its Effect.CSL, UIUC – p.6/23Modelx(t)y(t)x(t): number of downloaders, y(t): number of seedsλ: arrival rate of new requestsθ: the rate at which downloaders abort the downloadc : downloading bandwidth, µ: uploading bandwidth of apeerη: effectiveness parameter (Yang and de Veciana)γ: seed departure rateCSL, UIUC – p.7/23Modelx(t)y(t)λx(t): number of downloaders, y(t): number of seedsλ: arrival rate of new requestsθ: the rate at which downloaders abort the downloadc : downloading bandwidth, µ: uploading bandwidth of apeerη: effectiveness parameter (Yang and de Veciana)γ: seed departure rateCSL, UIUC – p.7/23Modelx(t)y(t)λθx(t)x(t): number of downloaders, y(t): number of seedsλ: arrival rate of new requestsθ: the rate at which downloaders abort the