Lecpeer2peer.ppt

Lecpeer2peer.ppt

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Spring2000Spring2002,CS461,1,Peer-to-PeerNetworks,OutlineSurveySelf-organizingoverlaynetworkFilesystemontopofP2PnetworkContributionsfromPeterDruschel,Spring2000Spring2002,Background,DistributionDecentralizedcontrolSelf-organizationSymmetriccommunication,Spring2000Spring2002,Examples,PioneersNapster,Gnutella,FreeNetAcademicPrototypesPastry,Chord,CAN,Spring2000Spring2002,CS461,4,CommonIssues,Organize,maintainoverlaynetworknodearrivalsnodefailuresResourceallocation/loadbalancingResourcelocationLocality（networkproximity）Idea:

genericp2psubstrate,Spring2000Spring2002,CS461,5,Architecture,TCP/IP,P2PSubstrate,Networkstorage,Eventnotification,Internet,self-organizingoverlaynetwork,P2papplicationlayer,?

Spring2000Spring2002,CS461,6,Pastry,Self-organizingoverlaynetworkConsistenthashingLookup/insertobjectinlog16Nroutingsteps（expected）O（logN）per-nodestateNetworklocalityheuristics,Spring2000Spring2002,CS461,7,ObjectDistribution,ConsistenthashingKargeretal.97128bitcircularidspacenodeIds（uniformrandom）objIds（uniformrandom）Invariant:

nodewithnumericallyclosestnodeIdmaintainsobject,Spring2000Spring2002,CS461,8,ObjectInsertion/Lookup,X,Route（X）,MsgwithkeyXisroutedtolivenodewithnodeIdclosesttoXProblem:

completeroutingtablenotfeasible,O,2128-1,Spring2000Spring2002,CS461,9,Routing,Propertieslog16NstepsO（logN）state,Spring2000Spring2002,LeafSets,EachnodemaintainsIPaddressesofthenodeswiththeLnumericallyclosestlargerandsmallernodeIds,respectively.routingefficiency/robustnessfaultdetection（keep-alive）application-specificlocalcoordination,Spring2000Spring2002,CS461,11,RoutingProcedure,if（destinationiswithinrangeofourleafset）forwardtonumericallyclosestmemberelseletl=lengthofsharedprefixletd=valueofl-thdigitinDsaddressif（Rldexists）forwardtoRldelseforwardtoaknownnodethat（a）sharesatleastaslongaprefix（b）isnumericallycloserthanthisnode,Spring2000Spring2002,CS461,12,Routing,Integrityofoverlay:

guaranteedunlessL/2simultaneousfailuresofnodeswithadjacentnodeIdsNumberofroutinghops:

Nofailures:

log16Nexpected,128/b+1maxDuringfailurerecovery:

O（N）worstcase,averagecasemuchbetter,Spring2000Spring2002,CS461,13,NodeAddition,Spring2000Spring2002,CS461,14,NodeDeparture（Failure）,Leafsetmembersexchangekeep-alivemessagesLeafsetrepair（eager）:

requestsetfromfarthestlivenodeinsetRoutingtablerepair（lazy）:

gettablefrompeersinthesamerow,thenhigherrows,Spring2000Spring2002,CS461,15,API,route（M,X）:

routemessageMtonodewithnodeIdnumericallyclosesttoXdeliver（M）:

delivermessageMtoapplicationforwarding（M,X）:

messageMisbeingforwardedtowardskeyXnewLeaf（L）:

reportchangeinleafsetLtoapplication,Spring2000Spring2002,PAST:

Cooperative,archivalfilestorageanddistribution,LayeredontopofPastryStrongpersistenceHighavailabilityScalabilityReducedcost（nobackup）Efficientuseofpooledresources,Spring2000Spring2002,CS461,17,PASTAPI,Insert-storereplicaofafileatkdiversestoragenodesLookup-retrievefilefromanearbylivestoragenodethatholdsacopyReclaim-freestorageassociatedwithafileFilesareimmutable,Spring2000Spring2002,CS461,18,PAST:

Filestorage,Spring2000Spring2002,CS461,19,PAST:

Filestorage,StorageInvariant:

File“replicas”arestoredonknodeswithnodeIdsclosesttofileId（kisboundedbytheleafsetsize）,Spring2000Spring2002,CS461,20,PAST:

FileRetrieval,fileId,filelocatedinlog16Nsteps（expected）usuallylocatesreplicanearestclientC,Lookup,kreplicas,C,