计算机科学技术进展讲座

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1、计算机科学技术进展讲座发展篇：HowtoBuildaPracticalP2Psystem当代篇：FromAcademytoIndustry历史篇：Structuralevolution概念篇：Advantages:WhyandWhat对等计算陈贵海2006年9月22日1Client/ServerModelisBeingChallengedNosingleserverorsearchenginecansufficientlycoverincreasingWebcontents.21018Bytes/yeargeneratedinInternet.Butonly3

2、1012Bytes/yearavailabletopublic(0.00015%).Googleonlysearches1.3108Webpages.(Source:IEEEInternetComputing,2001)概念篇2Client/ServerModelHasProblemsClient/servermodelseriouslylimitsutilizationofavailablebandwidthandservice.Popularserversandsearchenginesbecometrafficbottlenecks.Buthighspeed

3、networksconnectingmanyclientsbecomeidle.Computingcyclesandinformationinclientsareignored.概念篇3ContentDeliveryNetworks(CDN):ATransitionModelServersaredecentralized(duplicated)throughouttheInternet.Thedistributedserversarecontrolledbyacentralizedauthority(headquarters).Examples:Internetco

4、ntentdistributionsbyAkamai,Overcast,andFFnet.BothClient/ServerandCDNmodelshavesinglepointoffailures.概念篇4ANewParadigm:Peer-orientedSystemsBothclient(consumer)&server(producer).Hasthefreedomtojoinandleaveanytime.Hugepeerdiversity:serviceability,storagespace,networkingspeed,andservicedema

5、nd.Awidelydecentralizedsystemopeningforbothopportunitiesandnewconcerns.概念篇5Peer-orientedSystemsServerClient/servere.g.searchengine/gridPureP2Pe.g.Freenet&Gnutellae.g.NapsterHybridP2PdirectoryContentDeliveryNetworksServerDuplicatedServere.g.Akami概念篇6ObjectivesandBenefitsofP2PAslongasthe

6、renophysicalbreakinthenetwork,thetargetfilewillalwaysbefound.AddingmorecontentstoP2Pwillnotaffectitsperformance.(informationscalability).AddingandremovednodesfromP2Pwillnotaffectitsperformance.(systemscalability).概念篇7Peer-orientedApplicationsFileSharing:documentsharingamongpeerswithnoo

7、rlimitedcentralcontrols.InstantMessaging(IM):Immediatevoiceandfileexchangesamongpeers.DistributedProcessing:Onecanwidelyutilizeresourcesavailableinotherremotepeers.Wherearefurtherapplications?GridcomputingAdhocnetworkingWebcacheVoD……概念篇8WhatisP2PNetwork—Myversion[Equality]Allpeersass