虚拟专用网毕业论文外文翻译Word格式.docx
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虚拟专用网毕业论文外文翻译Word格式.docx
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Solutions,suchasthevariousencryptionmethodsandPKI,enablebusinessestosecurelyextendtheirnetworksthroughtheInternet.OnewayinwhichbusinessesaccomplishthisextensionisthroughVirtualPrivateNetworks(VPNs).
AVPNisaprivatenetworkthatiscreatedviatunnelingoverapublicnetwork,usuallytheInternet.Insteadofusingadedicatedphysicalconnection,aVPNusesvirtualconnectionsroutedthroughtheInternetfromtheorganizationtotheremotesite.ThefirstVPNswerestrictlyIPtunnelsthatdidnotincludeauthenticationorencryptionofthedata.Forexample,GenericRoutingEncapsulation(GRE)isatunnelingprotocoldevelopedbyCiscothatcanencapsulateawidevarietyofNetworkLayerprotocolpackettypesinsideIPtunnels.Thiscreatesavirtualpoint-to-pointlinktoCiscoroutersatremotepointsoveranIPinternetwork.OtherexamplesofVPNsthatdonotautomaticallyincludesecuritymeasuresareFrameRelay,ATMPVCs,andMultIProtocolLabelSwitching(MPLS)networks.
AVPNisacommunicationsenvironmentinwhichaccessisstrictlycontrolledtopermitpeerconnectionswithinadefinedcommunityofinterest.ConfidentialityisachievedbyencryptingthetrafficwithintheVPN.Today,asecureimplementationofVPNwithencryptioniswhatisgenerallyequatedwiththeconceptofvirtualprivatenetworking.
VPNshavemanybenefits:
●Costsavings-VPNsenableorganizationstousecost-effective,third-partyInternettransporttoconnectremoteofficesandremoteuserstothemaincorporatesite.VPNseliminateexpensivededicatedWANlinksandmodembanks.Additionally,withtheadventofcost-effective,high-bandwidthtechnologies,suchasDSL,organizationscanuseVPNstoreducetheirconnectivitycostswhilesimultaneouslyincreasingremoteconnectionbandwidth.
●Security-VPNsprovidethehighestlevelofsecuritybyusingadvancedencryptionandauthenticationprotocolsthatprotectdatafromunauthorizedaccess.
●Scalability-VPNsenablecorporationstousetheInternetinfrastructurethatiswithinInternetserviceproviders(ISPs)anddevices.Thismakesiteasytoaddnewusers,sothatcorporationscanaddsignificantcapacitywithoutaddingsignificantinfrastructure.
●Compatibilitywithbroadbandtechnology-VPNsallowmobileworkers,telecommuters,andpeoplewhowanttoextendtheirworkdaytotakeadvantageofhigh-speed,broadbandconnectivitytogainaccesstotheircorporatenetworks,providingworkerssignificantflexibilityandefficiency.High-speedbroadbandconnectionsprovideacost-effectivesolutionforconnectingremoteoffices.
Inthesimplestsense,aVPNconnectstwoendpointsoverapublicnetworktoformalogicalconnection.ThelogicalconnectionscanbemadeateitherLayer2orLayer3oftheOSImodel.VPNtechnologiescanbeclassifiedbroadlyontheselogicalconnectionmodelsasLayer2VPNsorLayer3VPNs.EstablishingconnectivitybetweensitesoveraLayer2orLayer3VPNisthesame.Adeliveryheaderisaddedinfrontofthepayloadtogetittothedestinationsite.ThischapterfocusesonLayer3VPNtechnology.
CommonexamplesofLayer3VPNsareGRE,MPLS,andIPSec.Layer3VPNscanbepoint-to-pointsiteconnectionssuchasGREandIPSec,ortheycanestablishany-to-anyconnectivitytomanysitesusingMPLS.
Genericroutingencapsulation(GRE)wasoriginallydevelopedbyCiscoandlaterstandardizedasRFC1701.AnIPdeliveryheaderforGREisdefinedinRFC1702.AGREtunnelbetweentwositesthathaveIPreachabilitycanbedescribedasaVPN,becausetheprivatedatabetweenthesitesisencapsulatedinaGREdeliveryheader.
PioneeredbyCisco,MPLSwasoriginallyknownastagswitchingandlaterstandardizedviatheIETFasMPLS.ServiceprovidersareincreasinglydeployingMPLStoofferMPLSVPNservicestocustomers.MPLSVPNsuselabelstoencapsulatetheoriginaldata,orpayload,toformaVPN.
HowdoesanetworkadministratorpreventeavesdroppingofdatainaVPN?
Encryptingthedataisonewaytoprotectit.Dataencryptionisachievedbydeployingencryptiondevicesateachsite.IPSecisasuiteofprotocolsdevelopedwiththebackingoftheIETFtoachievesecureservicesoverIPpacket-switchednetworks.TheInternetisthemostubiquitouspacket-switchedpublicnetwork;
therefore,anIPSecVPNdeployedoverthepublicInternetcanprovidesignificantcostsavingstoacorporationascomparedtoaleased-lineVPN.
IPSecservicesallowforauthentication,integrity,accesscontrol,andconfidentiality.WithIPSec,theinformationexchangedbetweenremotesitescanbeencryptedandverified.Bothremote-accessandsite-to-siteVPNscanbedeployedusingIPSec.
TherearetwobasictypesofVPNnetworks:
Site-to-site
Remote-access
Asite-to-siteVPNiscreatedwhenconnectiondevicesonbothsidesoftheVPNconnectionareawareoftheVPNconfigurationinadvance.TheVPNremainsstatic,andinternalhostshavenoknowledgethataVPNexists.FrameRelay,ATM,GRE,andMPLSVPNsareexamplesofsite-to-siteVPNs.
Aremote-accessVPNiscreatedwhenVPNinformationisnotstaticallysetup,butinsteadallowsfordynamicallychanginginformationandcanbeenabledanddisabled.ConsideratelecommuterwhoneedsVPNaccesstocorporatedataovertheInternet.ThetelecommuterdoesnotnecessarilyhavetheVPNconnectionsetupatalltimes.Thetelecommuter'
sPCisresponsibleforestablishingtheVPN.TheinformationrequiredtoestablishtheVPNconnection,suchastheIPaddressofthetelecommuter,changesdynamicallydependingonthelocationofthetelecommuter.
Asite-to-siteVPNisanextensionofaclassicWANnetwork.Site-to-siteVPNsconnectentirenetworkstoeachother,forexample,theycanconnectabranchofficenetworktoacompanyheadquartersnetwork.Inthepast,aleasedlineorFrameRelayconnectionwasrequiredtoconnectsites,butbecausemostcorporationsnowhaveInternetaccess,theseconnectionscanbereplacedwithsite-to-siteVPNs.
Site-to-siteVPN
Inasite-to-siteVPN,hostssendandreceivenormalTCP/IPtrafficthroughaVPNgateway,whichcanbearouter,firewall,CiscoVPNConcentrator,orCiscoASA5500SeriesAdaptiveSecurityAppliance.TheVPNgatewayisresponsibleforencapsulatingandencryptingoutboundtrafficfromaparticularsiteandsendingitthroughaVPNtunnelovertheInternettoapeerVPNgatewayatthetargetsite.UponreceIPt,thepeerVPNgatewaystrIPstheheaders,decryptsthecontent,andrelaysthepackettowardthetargethostinsideitsprivatenetwork.
Remote-AccessVPN
Remote-accessVPNsareanevolutionofcircuit-switchingnetworks,suchasplainoldtelephoneservice(POTS)orISDN.Remote-accessVPNscansupporttheneedsoftelecommuters,mobileusers,andextranetconsumer-to-businesstraffic.Remote-accessVPNssupportaclient/serverarchitecturewhereaVPNclient(remotehost)requiressecureaccesstotheenterprisenetworkviaaVPNserverdeviceatthenetworkedge.
Inthepast,corporationssupportedremoteusersbyusingdial-innetworksandISDN.WiththeadventofVPNs,amobileusersimplyneedsaccesstotheInternettocommunicatewiththecentraloffice.Inthecaseoftelecommuters,theirInternetconnectivityistypicallyabroadbandconnection.
Inaremote-accessVPN,eachhosttypicallyhasCiscoVPNclientsoftware.WheneverthehosttriestosendtrafficintendedfortheVPN,theCiscoVPNClientsoftwareencapsulatesandencryptsthattrafficbeforesendingitovertheInternettotheVPNgatewayattheedgeofthetargetnetwork.UponreceIPt,theVPNgatewaybehavesasitdoesforsite-to-siteVPNs.
Anemergingremote-accesstechnologyisCiscoIOSSSLVPN.Thistechnologyprovidesremote-accessconnectivityfromalmostanyInternet-enabledhostusingawebbrowseranditsnativeSecureSocketsLayer(SSL)encryption.SSLVPNsallowuserstoaccesswebpagesandservices,includingtheabilitytoaccessfiles,sendandreceiveemail,andrunTCP-basedapplicationswithoutIPSecVPNClientsoftware.Theyprovidetheflexibilitytosupportsecureaccessforallusers,regardlessofthehostfromwhichtheyestablishaconnection.Thisflexibilityenablescompaniestoextendtheirsecureenterprisenetworkstoanyauthorizeduserbyprovidingremote-accessconnectivitytocorporateresourcesfromanyInternet-enabledhost.
SSLVPNcurrentlydeliverstwomodesofaccess:
clientlessandthinclient.WithclientlessSSLVPN,aremoteclientneedsonlyanSSL-enabledwebbrowsertoaccessHTTP-orHTTPS-enabledwebserversonthecorporateLAN.InathinclientSSLVPNenvironment,aremoteclientmustdownloadasmall,Java-basedappletforsecureaccessofTCPapplicationsthatusestaticportnumbers.UDPisnotsupportedinathinclientenvironment.
SSLVPNsareappropriateforuserpopulationsthatrequireper-applicationorper-serveraccesscontrol,oraccessfromnon-enterprise-owneddesktops.SSLVPNsarenotacompletereplacementforIPSecVPNs.IPSecVPNsallowsecureaccesstoallofanorganization'
sclient/serverapplications.Additionally,SSLVPNsdonotsupportthesamelevelofcryptographicsecuritythatIPSecVPNssupport.WhileSSLVPNscannotreplaceIPSecVPNs,inmanycases,theyarecomplementarybecausetheysolvedifferentproblems.Thiscomplementaryapproachallowsasingledevicetoaddressallremote-accessuserrequirements.
TheprimarybenefitofSSLVPNsisthattheyarecompatiblewithDynamicMultIPointVPNs(DMVPNs),CiscoIOSFirewalls,IPSec,intrusionpreventionsystems(IPSs),CiscoEasyVPN,andNetworkAddressTranslation(NAT).
中文译文:
解决方案,如各种加密方法和PKI,使企业能够安全地通过互联网扩展其网络,实现这一企业网络扩展的方式之一就是通过虚拟专用网。
VPN通常是通过公共网络建立隧道的专用网络,VPN不是使用专用的物理连接,而是使用一个虚拟链路通过互联网实现远程站点到本地网络的连接,起初VPN的IP隧道中并不包含对身份验证和加
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