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History

TheP2ParchitectureembodiesakeyconceptofInternettechnology,whichwasdescribedinthefirstRFCdocument,HostSoftwareonApril7,1969.Underthegeneraltrendofexchangingmultimediafileswithoutacentralindexserverstructure,thisconcepthasbeenwidelypopularized.

Classification

Accordingtothedegreeofcentralization

  • PureP2P

    • Nodesactasbothclientandserveratthesametime.

    • Thereisnocentralserver.

    • Thereisnocentralrouter.

    • SuchasGnutella.

  • MiscellaneousP2P

    • Thereisacentralserverthatstoresnodeinformationandrespondstorequestsforthisinformation.

    • Nodesareresponsibleforpublishingthisinformation(becausethecentralserverdoesnotsavefiles),letthecentralserverknowwhatfilestheywanttoshare,andletthenodesthatneeditdownloaditssharableresources.

    • Theroutingterminalusestheaddresstoobtaintheabsoluteaddressbybeingreferencedbyasetofindexes.

    • LiketheoriginalNapster.

  • HybridP2P

    • ContainsthecharacteristicsofbothpureP2PandhybridP2P.

    • SuchasSkype.

Accordingtothenetworktopology

  • StructureP2P

    • Point-to-pointhaslinkinformationtoeachother,formingaspecificruletopologywitheachother.

    • Whenaresourceneedstoberequested,followthetopologyRulesearch,ifitexists,youmustfindit.

    • SuchasChord,YaCy,Kademlia.

  • NoneStructureP2P

    • Point-to-pointhaslinkinformationtoeachother,forminganirregularnetworktopologywitheachother.

    • Whenaresourcenodeneedstoberequested,itissearchedbybroadcast,usuallyTTLisset,evenifitexists,itmaynotbefound.

    • Forexample,Gnutella.

  • LooselystructuredP2P

    • Point-to-pointhaslinkinformationtoeachother,forminganirregularnetworktopologywitheachother.

    • Whenaresourceneedstoberequested,itisestimatedandsearchedbasedonexistinginformation,whichisbetweenstructuredP2PandunstructuredP2P.

    • SuchasFreenet.

AdvantagesofP2Pnetwork

AnimportantgoalofP2Pnetworkistoenableallclientstoprovideresources,includingbandwidth,Storagespaceandcomputingpower.Therefore,whenanodejoinsandrequestsforthesystemincrease,thecapacityoftheentiresystemalsoincreases.ThisisnotpossiblewiththeClient-Serverstructurewithasetoffixedservers,becauseintheabove-mentionedstructure,theincreaseofclientsmeansslowerdatatransmissionforallusers.

ThedistributednatureoftheP2Pnetworkalsoincreasestherobustnessoffailurepreventionbyreplicatingdataonmultiplenodes,andinapureP2Pnetwork,nodesdonotneedtorelyonacentralindexservertofinddata.Inthelattercase,thesystemwillnotcrashatasinglepoint.

WhenP2PisusedtodescribetheNapsternetwork,thepeer-to-peerprotocolisconsideredimportant,butinreality,theachievementoftheNapsternetworkisthatthepeernodes(justliketheendofthenetwork)uniteacentralindextofulfill.Thisallowsittolocateavailablecontentquicklyandefficiently.Thepeer-to-peerprotocolisjustageneralmethodtoachievethis.

Applications

Point-to-pointtechnologyhasmanyapplications.Itisverycommontosharefilescontainingvariousformatsofaudio,video,data,etc.Instantdata(suchasIPphonecommunication,Anychataudioandvideodevelopmentsoftware)canalsobetransmittedusingP2Ptechnology.

Somenetworksandcommunicationchannels,suchasNapster,OpenNAP,andIRC@find,useamaster-slavearchitecturestructuretohandlesometasks(suchassearchfunctions)ontheonehand,andP2PstructureontheotherhandTohandleothertasks.Somenetworks,suchasGnutellaandFreenet,usetheP2Pstructuretohandlealltasks,andaresometimesconsideredtobetrueP2Pnetworks.AlthoughGnutellaalsousesadirectoryservertofacilitatenodestogetthenetworkaddressesofothernodes.

AcademicP2Pnetwork

January28,2015,thedevelopersofPennsylvaniaStateUniversity,unitedtheMITOpenKnowledgeInitiative,SimonFraserUniversityResearchersfrom,andthesecond-generationInternetP2Pworkinggroup,aredevelopinganacademicapplicationofP2Pnetworks.ThisprojectiscalledLionShare,basedonthesecondgenerationofnetworktechnology,morespecificallytheGnutellamodel.Themainpurposeofthisnetworkistoallowusersfrommanydifferentacademicinstitutionstoshareacademicmaterials.TheLionSharenetworkusesahybridP2Pnetworktype,whichisamixtureofGnutella'sdecentralizedP2PnetworkandthetraditionalC/Snetwork.Usersofthisprogramcanuploadfilestoaserver,regardlessofwhethertheuserisonline,theycancontinuetoshare.Thisnetworkalsoallowsuseinsharedcommunitiesthataremuchsmallerthannormal.

ThemaindifferencebetweenthisnetworkandotherP2PnetworkscurrentlyinuseisthattheLionSharenetworkdoesnotallowanonymoususers.Thepurposeofthisistopreventcopyrightedmaterialsfrombeingsharedonthenetwork,whichalsoavoidslegaldisputes.Anotherdifferenceistheselectivesharingofindividualfilesfordifferentgroups.Theusercanindividuallyselectwhichuserscanreceivethisfileorgroupoffiles.

Theacademiccommunityneedsthistechnologybecausemoreandmoremultimediafilesareusedintheclassroom.Moreandmoreprofessorsusemultimediafiles,likeaudiofiles,videofilesandslideshows.Passingthesefilestostudentsisadifficulttask,anditismucheasierifyouuseanetworklikeLionShare.

Advantages

  • Hasbetterparallelprocessingcapabilities.

  • Usingmemorytomanageexchangedata,greatlyimprovingperformance.

  • Noneedtoinvestalotofmoneyintheserver'ssoftwareandhardwareequipment.

  • Suitableforsmall-scalenetworks,easytomaintain.

Disadvantages

  • Thesetupismorecomplicated.Inadditiontoadevelopmentserver,italsoneedsadedicatedclient.

  • Usedinlarge-scalenetworks,resourcesharingisdisordered,managementisdifficult,andsecurityislow.

Disputes

Legalaspects

InUSlaw,the"Betamaxjudgment"precedentinsiststhatcopying"technology"isnottheessenceIllegal,iftheyhaveasubstantivenon-infringinguse.ThisdecisionbeforethewidespreaduseoftheInternetisappliedtomostdatanetworks,includingP2Pnetworks,becausethedisseminationofapproveddocumentsisalsopossible.Theseillegalandinfringingusesincludeopensourcesoftware,publicdomainfiles,andworksnotcoveredbycopyright.Otherjudicialdepartmentscanviewthissituationinasimilarway.

Infact,mostofthefilessharedonP2Pnetworksarecopyrightedpopularmusicandmovies,includingvariousformats(MP3,MPEG,RM,etc.).Inmostjurisdictions,sharingthesecopiesisillegal.Thishascausedmanyobservers,includingmostmediacompaniesandsomeP2Padvocates,tocriticizethisnetworkasahugethreattotheexistingdistributionmodel.Studiesthatattempttomeasureactualmonetarylossesaresomewhatunclear.Althoughtheexistenceofthesenetworksonpapercausedalotoflosses,infact,sincetheestablishmentofthesenetworks,theactualincomehasnotchangedmuch.Regardlessofwhetherthisthreatexists,theRecordingIndustryAssociationofAmericaandtheMotionPictureAssociationofAmericaarespendingalotofmoneytryingtolobbylawmakerstocreatenewlaws.Somecopyrightownersalsopaycompaniestohelplegallychallengeuserswhoengageinillegalsharingoftheirmaterials.

DespitetheBetamaxverdict,P2Pnetworkshavebecometargetsofattacksbyartistsandrepresentativesofcopyrightlicensingorganizations.ThisincludesindustryorganizationssuchastheRecordingAssociationofAmericaandtheMotionPictureAssociationofAmerica.TheNapsterservicewasforcedtoshutdownduetoacomplaintfromtheRecordingAssociationofAmerica.Inthiscase,Napsterdeliberatelyboughtandsoldtheseaudiovisualfilesthatwerenotlicensedfromthecopyrightowner.

Withtheexpansionofmediacompanies’effortstocombatcopyrightinfringement,thesenetworkshaverapidlyandcontinuouslyadjusted,makingitdifficulttoremovethembothtechnicallyandlegally.Thisleadstouserswhoreallyviolatethelawbeingtargeted,becausealthoughtheunderlyingtechnologyislegal,itsabusebyindividualswhospreaditinawayofinfringingcopyrightisobviouslyillegal.

AnonymousP2Pnetworkallowsthepublicationofmaterials,nomatterlegalorlegal,thereislittleornolegalresponsibilityinvariousjurisdictions.Manypeoplesaythatthiswillleadtomoreillegalmaterialsmoreeasilyspread,andeven(somepeoplepointedout)promoteterrorism,requiringregulationintheseareas.Othersobjectedthatthepotentialforillegalusecannotpreventtheuseofthistechnologyforlegitimatepurposes,andthepresumptionofinnocencemustbeapplied,asothernon-P2Panonymousservices,suchasemail,havesimilarcapabilities.

Importantcase:

  • U.S.law

    • SonyCorp.vsUniversalCityStudios(Betamaxverdict)

    • MGMvsGrokster

Securityaspects

ManyP2PTheInternethasbeencontinuouslyattackedbypeoplewithvariouspurposes.Examplesinclude:

  • Poisoningattacks(providingfileswithdifferentcontentanddescription)

  • Denialofserviceattacks(makingthenetworkveryslowEvencrashcompletely)

  • Betrayalattack(bloodsucking)(usersorsoftwareusethenetworkwithoutcontributingtheirownresources)

  • Insertavirusintothedata(forexample,thedownloadedortransferredfilemaybeinfectedwithavirusoraTrojanhorse)

  • TheTrojanhorseoftheP2Psoftwareitself(forexample,thesoftwaremaycontainspyware)

  • Filtering(networkoperatorsmaytrytoprohibitthetransmissionofdatafromP2Pnetworks)

  • Identityattacks(e.g.,Trackingusersonthenetworkandcontinuouslyharassingorattackingthemlegally)

  • Spam(suchassendingunsolicitedinformationonthenetwork--notnecessarilyDenialofserviceattack)

IfP2Pnetworkiscarefullydesignedandencryptiontechnologyisused,mostoftheattackscanbeavoidedorcontrolled.P2PnetworksecurityisinfactcloselyrelatedtotheByzantinegeneralproblemconnect.However,whenmanynodestrytodestroyit,almostanynetworkwillfail,andmanyprotocolswillfailbecauseoffewerusers.

OnApril23,2007,CAissuedaninformationsecurityalert,pointingoutFoxy,BitComet,eDonkey,µTorrent,Ares,Azureus,BearShare,Lphant,Shareaza,Hamachi,exeemlite,Fpsetup,Morpheus,iMeshThe14typesofP2Psoftwarehavesecuritythreats.ThepotentialthreatsourcesoftheseP2Psoftwareincludethepossibilityofoverwritingfiles,renamingfiles,deletingfiles,andimplantingmaliciousprogramsbythirdparties.

FutureofComputingTechnology

Strictlyspeaking,fromatechnicalperspective,bothpartiesinapeer-to-peernetworkarestrictlypeersandprovideandusedataequally,andthereisnodifferencebetweenaserverandaclient.ButsuchpureP2Papplicationsandnetworksarefewandfarbetween.MostofthenetworksandapplicationscalledP2Pactuallyrelyonorincludesomenon-peerunitslikeDNS.Atthesametime,multipleprotocolsareactuallyusedintheapplication,sothatnodescanbecomeclients,servers,andpeernodesatthesametimeortime-sharing;forexample,Usenet(1979)andFidoNet(1984)havebeenusedformanyyears,suchascompletelydistributedpairs.Waitforthenetwork.

ManyP2Psystemsusestrongerpeers(calledSuperNodes)asservers,andthoseclientnodesareconnectedtoasuperpeerinastar-likemanner.

Inthelate1990s,beforeinstantmessagingbecamepopular,inordertopromotethedevelopmentofpeer-to-peernetworkapplications,SunSun(SUN)addedsomeclassestoJavatechnology.Sothatdeveloperscandevelopreal-timechatappletsandapplicationsthatarenotcontrolledbythecentralserver.ThisworkiscontinuedbytheJXTAproject.

P2Psystemsandapplicationshaveattractedalotofattentionfromcomputerscienceresearch.Inthisfield,thereareChordProject,ARPANET,thePASTstorageutility,andP-Grid(aspontaneouslyorganizedemergingcoveragenetwork),AndaseriesofoutstandingresearchprojectsincludingtheCoopNetcontentdistributionsystem.

Restrictions

ThePeople’sRepublicofChina

P2PtechnologyisinablankstateintermsofChineselawsandinprincipleisnotsubjecttoofficialrestrictionsbytheChinesegovernment.However,becauseP2Ptechnologywilloccupyalargeamountofnetworkbandwidth,andbecauseofthecurrentstatusofChina'snetworkfacilitiesandChina'sattitudetonetworkmanagement,therearevaryingdegreesofrestrictionsonP2Pcommunicationmethods.

AllmajorISPsinChinahaveimposedspeedlimitsonnetworkaccess,andwilltakemeasuresforbandwidth-consumingapplicationssuchasP2P.CommonmethodsincludelimitingthenumberofTCPconnections,blockingtheP2Pprotocol,andrestrictingdownloads/uploads.Speed​​etc.However,becausemostoftheseactionsarecarriedoutinsecret,manyP2PusersinChinaclaimthatthishasseriouslyviolatedtheirrighttoknowanduse.InChina,themostrestrictedP2PsoftwareisBitTorrentseriessoftwareandeMule.

InthecaseofincreasinglyscarceIPv4addressresources,mostareasofChinahavebeguntoadoptthe"largeintranet"approachtoreducetheconsumptionofIPaddressresources,thatis,mosthouseholdsandindividualuserswillconnectTherouteroftheISPusesnetworkaddresstranslationtoconnecttotheexternalnetwork.DuetothelimitationsofNATandsomeP2Pprotocols,mostP2Psoftwarecanonlybetransmittedontheintranet,whichhasagreatimpactontheP2Pindustrychain.

Inaddition,outofconsiderationofdomesticindustrysupportandinformationcontrol,ChinawillalsorestrictsomeP2Pinstantmessagingsoftware.TheMinistryofInformationIndustryofChinahasissuedadocumentrequestingthatVOIPcanonlybetestedondesignatednetworkoperators,andskypeisblockedinsomeareas,butsomeofficialshavedeniedthisandstatedthatitisonlyforPC-Phone.

InDecember2009,theMinistryofIndustryandInformationTechnologyrevokedtherecordnumberoftheBtchinawebsiteonthegroundsofignoringtheaudiovisuallicenseandforcedittoclosethestation.TheactionalsoaffectedBTsitesincludingYoyoBirdForum.

Japan

InJapan,accordingtoJapan'scurrentcopyrightlaw,allwebsitesinJapanthatprovidefreecommercialsoftware/orotherdatadownloadsareillegal.Seriousviolationscanbesentencedtofixed-termimprisonmentandafine.BothBitTorrentseriessoftwareandeMulearebanned.ButbecauseoftheexistenceofShareandWinnysoftware,P2PtechnologyisstillpopularinJapan.BothsoftwareusesIPencryptionanddataencryptiontechnology.MillionsofpeopleinJapanusethesetwosoftwaretoexchangeanimation,games,music,softwareandotherdata,butitisclearthatthepolicehavetakencontrolofthemethodoftracingusers.OnMay9,2008,threeworkerswhopostedalargenumberofcopyrightedworksonsharewerearrested.Thepopularityofthesetwosoftwarehasalsobroughtsomenegativeproblems,suchastheleakageofconfidentialinformationandthespreadofcomputerviruses.

NewZealand

InNewZealand,accordingtoNewZealand'sSeptember2011copyrightlaw,downloadingcopyrightedcontentinNewZealandisillegal,anditismainlyaimedatdownloadingP2Ptechnology.Ifthedownloadedcontentreceivesacomplaintfromthecopyrightparty,theISPwillevaluateitbasedonthetimetheuserisdownloading.Ifthereiscopyrightinfringement,theuserwillbewarned.Threewarningswillresultinafineof15,000NewZealanddollars,whichisapproximately75,000RMB.However,itshouldbenotedthatonlineviewingandfilehostingwebsitesarenotwithinthescopeofthisfine.Inotherwords,usersmaybefinediftheydownloadacopyright-protectedworkthroughthetorrentsofTorrentsoftware,buttheywillnotbepunishediftheyuseofflinefiledownloadmethods.Moreover,thecopyrightholdersreceivingcopyrightprotectioninNewZealandusuallyonlyincludesomeEuropeanandAmericancompanies,soforlocalChinese,eveniftheyusep2ptechnologytodownloadChina,SouthKoreaandotherAsianvarietymovieswillnotbesued.

See

  • Foxy

  • eMule

  • BitTorrentProtocol

  • BitTorrentProtocolSpecification

  • I2P

  • DecentralizedNetwork

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