Síťové charakteristiky
Peer-to-peernetworkisanetworkstructureidea.Anessentialdifferencebetweenitandthecurrentdominantclient/server(Client/Server)structure(thatis,thestructureadoptedbytheWWW)inthecurrentnetworkisthatthereisnocentralnode(orcentralserver)intheentirenetworkstructure.IntheP2Pstructure,eachnode(peer)mostlyhasthreefunctionsatthesametime:informationconsumer,informationprovider,andinformationcommunication.Intermsofcomputingmode,P2PbreaksthetraditionalClient/Server(C/S)mode,andthestatusofeachnodeinthenetworkisequal.Eachnodenotonlyactsasaserver,providesservicesforothernodes,butalsoenjoystheservicesprovidedbyothernodes.
Simplyput,P2Pistoconnectpeopledirectly,allowingpeopletointeractdirectlythroughtheInternet.P2Pmakescommunicationonthenetworkeasier,moredirectsharingandinteraction,andtrulyeliminatesmiddlemen.
AnotherimportantfeatureofP2PistochangethecurrentEthernetstation-centricstateoftheInternet,returnto"decentralization",andreturnpowertousers.
Thepeer-to-peernetworkisasuccessfulexpansionofthedistributedconcept.Itdistributestheburdenoftheserverinthetraditionalwaytoeachnodeinthenetwork,andeachnodewillundertakelimitedstorageandcomputingtasks.Themorenodesthatareaddedtothenetwork,themoreresourcesthenodescontribute,andthehigherthequalityoftheirservices.
Peer-to-peernetworkscanuserelativelypowerfulcomputers(personalcomputers)thatexistattheedgeoftheInternettoperformmoreadvancedtasksthanclient-basedcomputingtasks.ModernPCshaveextremelyfastprocessors,massiveamountsofmemory,andlargeharddrives,andtheycannotfullyexploitthepotentialofthesedeviceswhenperformingroutinecomputingtasks(suchasbrowsinge-mailandtheWeb).ModernPCscaneasilyactasclientsandservers(peers)formanytypesofapplicationsatthesametime.
ThecharacteristicsofP2Pnetworktechnologyarereflectedinthefollowingaspects:
Decentralizace
Theresourcesandservicesinthenetworkarescatteredonallnodes,andtheinformationisTherealizationoftransmissionandservicesarecarriedoutdirectlybetweennodes,withouttheinterventionofintermediatelinksandservers,andpossiblebottlenecksareavoided.ThedecentralizedbasiccharacteristicsofP2Pbringitsadvantagesinscalabilityandrobustness.
Škálovatelnost
InaP2Pnetwork,asusersjoin,notonlydoesthedemandforservicesincrease,buttheoverallsystemresourcesandservicecapabilitiesarealsoexpandingsimultaneously,alwaysItiseasiertomeettheneedsofusers.Intheory,itsscalabilitycanbeconsideredalmostunlimited.Forexample:InthetraditionalwayofdownloadingfilesviaFTP,whendownloadingusersincrease,thedownloadspeedwillbecomeslowerandslower.However,theP2Pnetworkisjusttheopposite.Themoreusersjoin,themoreresourcesareprovidedintheP2Pnetwork.,Thedownloadspeedisfaster.
Robustnost
P2Parchitectureisinherentlyresistanttoattacksandhighlyfault-tolerant.Sincetheserviceisdistributedamongvariousnodes,thedestructionofsomenodesorthenetworkwillhavelittleimpactonotherparts.P2Pnetworksgenerallycanautomaticallyadjusttheoveralltopologywhensomenodesfailtomaintaintheconnectivityofothernodes.P2Pnetworksareusuallyestablishedinaself-organizingmannerandallownodestojoinandleavefreely.
Vysoký výkon
PerformanceadvantageisanimportantreasonwhyP2Piswidelyconcerned.Withthedevelopmentofhardwaretechnology,thecomputingandstoragecapacityofpersonalcomputers,aswellastheperformanceofnetworkbandwidth,haveincreasedrapidlyinaccordancewithMoore'stheorem.AdoptingtheP2ParchitecturecaneffectivelyutilizealargenumberofordinarynodesscatteredontheInternet,anddistributecomputingtasksorstoreddatatoallnodes.Utilizetheidlecomputingpowerorstoragespacetoachievethepurposeofhigh-performancecomputingandmassstorage.Atpresent,theapplicationofP2Pinthisareaismostlyinacademicresearch.Oncethetechnologyismatureandcanbepromotedintheindustrialfield,itcansavemanycompaniesthecostofpurchasinglarge-scaleservers.
Ochrana soukromí
InaP2Pnetwork,becausethetransmissionofinformationisdispersedamongnodeswithoutgoingthroughacentralizedlink,theuser’sprivateinformationmaybeeavesdroppedandleakedSexisgreatlyreduced.Inaddition,thecurrentmethodofsolvingInternetprivacyproblemsmainlyadoptsrelayandforwardingtechnology,thushidingcommunicationparticipantsinnumerousnetworkentities.Insometraditionalanonymouscommunicationsystems,therealizationofthismechanismreliesoncertainrelayservernodes.InP2P,allparticipantscanprovidethefunctionofrelaying,whichgreatlyimprovestheflexibilityandreliabilityofanonymouscommunication,andcanprovideuserswithbetterprivacyprotection.
Vyvažování zátěže
IntheP2Pnetworkenvironment,sinceeachnodeisbothaserverandaclient,itreducestherequirementsforthecomputingandstoragecapabilitiesofthetraditionalC/Sstructureserver.Theresourcesaredistributedacrossmultiplenodes,whichbetterrealizestheloadbalanceoftheentirenetwork.
Becausethepeer-to-peernetworkdoesnotrequireadedicatedserverfornetworksupport,andothercomponentsarenotneededtoimprovetheperformanceofthenetwork,thenetworkingcostislow,anditissuitableforscenarioswithfewpersonnelandsimplenetworking.,Soitisoftenusedinsmallandmedium-sizedenterprisesorhomeswithsmallnetworks.
Výhody a nevýhody
Výhody
Ve srovnání se sítěmi typu klient/server mají sítě typu peer-to-peer následující výhody:
1Contentandresourcescanbesharedinthecentralandperipheralareasofthenetwork.Inaclient/servernetwork,contentandresourcescanusuallyonlybesharedinthecentralareaofthenetwork.
2.Thenetworkcomposedofpeersiseasytoexpandandmorereliablethanasingleserver.Asingleserverwillbesubjecttoasinglepointoffailure,orwillbecomeabottleneckwhenthenetworkusageishigh.
3.Anetworkcomposedofpeerscanshareprocessorsandintegratecomputingresourcestoperformdistributedcomputingtasks,ratherthanrelyingsolelyonacomputer,suchasasupercomputer.
4.Theusercandirectlyaccessthesharedresourcesonthepeer-to-peercomputer.Thepeersinthenetworkcandirectlysharefilesonthelocalstorageinsteadofsharingonthecentralserver.
Nedostatečná
1. Ovlivňuje výkon uživatelského počítače
Thecomputerinthepeer-to-peernetworkneedstoundertakeboththeserverandtheworkstationatthesametime,whichmakestheoriginalThesingle-usercomputerofisusedasamulti-usercomputer.Whenlarge-scaledataexchangeiscarriedout,theperformanceofthenetworkwillbegreatlyaffected.
2.Špatné zabezpečení sítě
Inapeer-to-peernetwork,resourcesarenotstoredcentrallyinsomecomputers,butarescatteredthroughoutthenetwork,andareManagedbyusers,thereisnoguaranteethatalluserscanprotecttheirresources.Inaddition,themanagementofuseraccountsandpasswordsinapeer-to-peernetworkisalsoanimportantissue.Auserhastomemorizemultiplesetsofaccountsandpasswordstoaccessresourcesindifferentcomputers.
3. Potíže se zálohováním a obnovou zdrojů
Resourcesinpeer-to-peernetworksarerelativelyscattered,anditismorecomplicatedtobackupandrestoreresourcesinallcomputers.Duetotheabovecharacteristics,peer-to-peernetworksaresuitableforoccasionswithfewusers,smallscale,andlowsecurityperformancerequirements.
Hlavní režim
P2Pnetworkismainlybasedontwomostbasicmodes,namelycentralizeddirectorymodeandnon-centralizeddirectorymode.
Centralized DirectoryMode
Thecentralizeddirectory-basedP2PmodeisalsocalledthestructuredP2Pmode.Inthismode,acentralserverissetuptorecordandmanagethesharedinformationresourcesofallnodes.Eachpeernodequeriestheservertoknowwhichnodeinthepeer-to-peernetworkhasthesharedinformationresourcesitneeds.Afterfindingit,obtainsitshostaddress,andthenfurtherrequeststheinformationresourcesitneedsfromthehost.Finally,thehostwillcopyitssharedinformationandsendittotherequestinghost’scentralizeddirectoryP2Pnetwork.
Necentralizovaný adresářový režim
TheP2Pmodeofnon-centralizeddirectoryisalsocalledpureP2Pmode.Inthenon-centralizedP2Pmodel,thepeer-to-peernetworkdoesnotneedtosetupacentralservertorecordandmanagethesharedinformationresourcesofallnodes.Toobtainasharedinformationresource,anynodefirstaskswhetheritsneighboringnodehastheresource.Ifaneighboringnodedoesnot,itwillfurtheraskitsneighboringnode(theinquirymessagemustIncludingtheaddressoftheinitialrequestingnode),untilthenodewiththeinformationresourcereceivestheinquiryrequest,thenthisnodewillgiveanaffirmativeresponsetotheinitialrequestingnode(andspecifyitsownaddressatthesametime).Finally,theinitialrequestingnodemakesaresourcerequesttothisnode,andthenodecopiesitssharedinformationandsendsittotheinitialrequestingnode.
Identifikační metoda
CurrentcommunicationmodesincludeClient/Server,Brower/ServerandSlave/Master.Forexample,thecorporateLANIntranetandInternetbothuseClient/ServerandBrowser/Serverasthemodel,whiletheearlyhostsystemadoptstheSlave/Mastermodel.Thecharacteristicsofthesemodesare:theyareallbasedontheapplication,theremustbeanapplicationserverinthenetwork,theuser'srequestmustbecompletedthroughtheapplicationserver,andthecommunicationbetweenusersmustalsogothroughtheserver.Inapeer-to-peernetwork,userscancommunicatedirectly,shareresources,andworktogether.
Síťové kroky
1.Určete topologii sítě.
2. Vyberte si vhodné přenosové médium.
3.Selectnetworkconnectionequipmentaccordingtothetypeoftransmissionmedium,theoperatingspeedofthenetwork,andthecoverageofthenetwork.
4.Hardwarové připojení.
5. Instalace a konfigurace síťového softwaru.
6.Nastavení sdílení zdrojů.
Typy softwaru
Currently,P2Pnetworkcomputingtechnologyiscontinuouslybeingappliedtomilitary,commerce,governmentaffairs,telecommunications,communicationsandotherfields.Accordingtodifferentspecificapplications,P2Papplicationsoftwarecanberoughlydividedintothefollowingtypes:
1.Sdílení a stahování obsahu souborů, jako jsou Napster, Gnutella, eDonkey, eMule, Maze, BT atd., mohou uživatelé přímo stahovat z libovolného počítače s nainstalovaným podobným softwarem a načítat a kopírovat sdílené soubory.
2.Výpočetní výkon a sdílení úložiště, jako je SETI@home, Avaki, PopularPower, Netbatch, Farsite atd., lze použít k distribuci objektů úložiště v síti nebo k využití jejich volného času pro společné výpočty.
3.Platformy pro společné zpracování a sdílení služeb založené na technologii P2P, jako jsou JXTA, Magi, Groove atd., lze použít pro řízení podniku.
4.Nástroje pro rychlé zasílání zpráv, včetně ICQ, QQ, YahooMessenger, MSNMessenger atd., může více uživatelů komunikovat prostřednictvím textu, hlasu nebo souborů a dokonce komunikovat s mobilními telefony.
5.P2P komunikace a sdílení informací, jako je Skype, Davy, OnionRouting atd.
6.NetworkTV a online hry založené na technologii P2P, jako je BoilingPoint, PPStream, PPLive, QQLive, SopCast atd. Mnoho aktuálních online her je implementováno prostřednictvím sítí peer-to-peer.
Technické normy
Inrecentyears,withtherapidspreadofP2Ptechnology-basedfilesharingsoftwaresuchasNapster,KaZaa,BT,andeMuleontheInternet,P2Ptechnologyhasbeentriggeredbothathomeandabroad.Anewwaveofresearch.
Mezinárodní
Currently,thereisnouniformstandardforinternationalpeer-to-peernetworks.AP2PworkinggroupwasestablishedinAugust2000,withmembersincludingIntel,IBM,andHP.Othermajorobstaclestothedevelopmentofpeer-to-peernetworksincludecopyrightissues,networkbandwidthissues,managementissues,andsecurityissues.Howtoconnectphones,mobilephonesandhomeappliances,industrialequipment,etc.,isalsoaproblemthatneedstobesolvedinpeer-to-peernetworks.
Domácí
DomácícompanieshavebeenkeepingpacewiththeworldinthefieldofP2Papplicationresearch,andhavedevelopedmanywidelyusedP2Pproducts.Theseproductsaremainlyconcentratedinfilesharinganddownloading,networkstreamingTVandsoon.
POCO
POCOisChina’sleadingfreemovie,music,animationandothermultimediasharingplatform,andthenumberofpeopleonlineatthesametimeexceedsthenumberWith700,000people,itisChina'slargestmovie,music,andanimationsharingplatform.Itisathird-generationP2Presourceexchangeplatformwithflowcontrolandnocentralserver.POCOprovidestechnologiessuchasmulti-pointtransmissionandresumabletransmissiontoensuretheefficiencyandstabilityofthetransmissionprocess.
OP
Tothemusic,movies,software,games,pictures,booksandvariousdocumentsyouwant,Thefilecapacityofhundredsofmillionsoffilescanbesharedonlineatanytime.OPintegratesInternetExplorer,WindowsMediaPlayer,RealOnePlayerandACDSee,andisadomesticonlineentertainmentcontentplatform.
PPLive
PPLiveisasharingsoftwareforlarge-scalelivevideostreamingontheInternet.Itusesthemeshmodeltoeffectivelysolvethebandwidthandloadlimitationofthecurrentnetworkvideo-on-demandservice.Themoreusers,thesmoothertheplayback,andtheoverallservicequalityisgreatlyimproved.
Aplikační výzkum
P2Pdistribuovaný úložný systém
P2Pdistribuovaný úložný systém(filesharinganddownloading)isadatastoragesystemforpeer-to-peernetworks,Itcanprovideefficient,robustandload-balancedfileaccessfunctions.Forstoragesystems,userscareabouttheefficiencyofdatalocation,search,androuting,andsecurityisalsoanimportantfactor.Inmanycases,thecentralizedmethodisnolongersuitableforthislarge-scaledatastoragerequirement,whichrequiresanewsystemtomanagethedatainthesystem.P2Pdistribuovaný úložný systémistosolvesuchproblems.Thesestudiesincludefullydistributedstoragesystems:Oceanstore,PastandFreeHaven,etc.Amongthem,semi-distributedP2Papplicationsbasedonthesuper-pointstructuresuchasKaZaa,Edonkey,Morpheus,BitTorrent,etc.alsobelongtothecategoryofP2Psharedstorage,andthenumberofusershasincreasedsharply.BothOceanstoreandPastprovideaneffectiveWANstoragemodel.TheirbottomlayerhasestablishedaroutingstrategywithacostupperlimitoflogN.Pastisorientedtoarelativelysimpleandcompactconcept.ItusestheroutingmechanismprovidedbyPastrytotrytouseidlestoragenodesinthenetworktoestablishamorecompletestoragesemantics.FreeHavenhasestablishedadetailedanonymitysystemtopreventpotentialmaliciousattacks.
Sdílení výpočetního výkonu P2P
Inadditiontosharingstoragecapabilities,nodesthatjoinapeer-to-peernetworkcanalsoshareCPUprocessingcapabilities.Therearealreadysomecomputingpowersharingsystemsbasedonpeer-to-peernetworks,suchasSETI@home.SETI@homeisaresearchprojectcarriedoutbytheUniversityofCalifornia,Berkeleytofindalienlife.ItusesP2Ptechnologytoconnectallidlecomputersparticipatingintheresearchprojecttoperformcomplexcalculationstoanalyzeradiosignalsfromplanetsandfindevidencethatotheraliencivilizationsmayexistintheuniverse.Theaveragedailyperformanceofthesecomputersexceedsthehighestcostintheworld.,Thefastestsupercomputer.Thiscomputingpowersharingsystemcanalsobeusedforapplicationsthatrequirelarge-scalecomputingpower,suchasgeneticdatabaseretrievalandpasswordcracking.
Vývojový trend
IntermsofP2Pcollaborativecomputing,domesticenterprisesstartedlate.Therearenotmanyrelatedproducts,andforeigncountriessuchasGroovehavedonealotofworkinthisareaanddevelopedrelativelymatureproducts.Withtheriseoftheconceptofcollaborativecomputing,thedemandforsoftwareinthisareaisshowingatrendofrapidgrowth,anditshouldbeavastocean.Moreover,thistypeofsoftwareisoftengearedtowardsenterpriseandgovernmentusers,soithasbetterprofitmarginsthanfreeP2Pfilesharingsoftware.
IntermsofP2Pstreamingmediatechnology,atpresent,theresearchonstreamingmediatransmissionhasjuststarted,andtherearestillmanyproblemstobesolved.SincethebehaviorofnodesintheP2PstreamingmediasystemisofAd-Hocnature,howtoensurethequalityofserviceofstreamingmediainadynamicsystemenvironmentneedstocombinetheknowledgeofstreamingmedia’sQoSrequirementsandnetworktrafficanalysistostudyhighefficiency,Low-costQoSguaranteemechanism.Researchabledirectionsinclude:theselectionofservicenodes,howtoensurethecontinuityofstreamingmediaserviceswhenanodefails,andthetransmissionschedulingofmultiplesenders.
ThegreatsuccessofSkype,aVoIPproductbasedonP2Ptechnology,hasopenedupanothernewfieldforP2P.RelevantexpertsbelievethatthereshouldbetworoadsforthedevelopmentofVOIP.Oneistherouteoftraditionaltelecomoperators,namely,theestablishmentofanIMSplatformonamanageableIPnetworktodevelopVoIPvoiceservices.Thiskindofnetworkisclosedandmanageable.TheotherisapublicP2PVoIPnetworkbasedontheexistingInternetpublic.Itischaracterizedbyopenness,anyonecanfreelyjoinandleavethenetwork,hasdistributedmanagementandgrowthcapabilities,andanydevicecanbeusedaslongasitsupportsstandardprotocols.Theinterestneedsoftraditionaltelecomoperatorsandtheneedsofusershavebecomeacontradiction,buttheneedsofthemarketandthedevelopmenttrendofVOIPcannotbechanged.Itisstilluncertainwhichpathwillbeadoptedinthefuture.Itdependsondevelopmentandcompetition.TheremaybemanylargecorporatecustomersandgovernmentagenciesthathavespecialrequirementsforsecurityandwilluseVOIPservicesestablishedbytelecomoperators.However,forordinaryusers,P2PVoIPnetworksbasedonthepublicInternetwillbethegeneraltrend.
Tosumup,P2Ptechnologyisinthespringofdevelopment.Killerapplicationsbasedonthistechnologywillcontinuetoemerge.ThesetechnologieswillgreatlyimprovetheappearanceoftheentireITworld,whichcanbesaidtobetheInternet.Anothernewrevolutionintechnology.