计算机英语毕业论文.doc

计算机英语论文Newtechniqueofthecomputer networkNewtechniqueofthecomputernetworkAbstractThe21centuryisanagesoftheinformationeconomy,beingthecomputernetworktechniqueofrepresentativetechniquesthisages,willbeatveryfastspeeddevelopsoonincontinuouslycreatively,andwillgodeepintothepeople#39;swork,lifeandstudy.Therefore,controlthistechniqueandthenseemtobemoretodelivertheimportance.NowImainlyintroducethenewtechniqueofafewnetworksinactualityliveofapplication.keywordsInternetDigitalCertificatesDigitalWalletsGridStorage1.ForewordInternetturns36,stillaworkinprogressThirty-sixyearsaftercomputerscientistsatUCLAlinkedtwobulkycomputersusinga15-footgraycable,testinganewwayforexchangingdataovernetworks,whatwouldultimatelybecometheInternetremainsaworkinprogress.Universityresearchersareexperimentingwithwaystoincreaseitscapacityandspeed.ProgrammersaretryingtoimbueWebpageswithintelligence.Andworkisunderwaytore-engineerthenetworktoreducespam(junkmail)andsecuritytroubles.Allthewhilethreatsloom:Criticswarnthatcommercial,legalandpoliticalpressurescouldhinderthetypesofinnovationsthatmadetheInternetwhatitistoday.StephenCrockerandVintonCerfwereamongthegraduatestudentswhojoinedUCLAprofessorLenKleinrockinanengineeringlabonSept.2,1969,asbitsofmeaninglesstestdataflowedsilentlybetweenthetwocomputers.ByJanuary,threeothernodesjoinedthefledglingnetwork.Thencamee-mailafewyearslater,acorecommunicationsprotocolcalledTCP/IPinthelate70s,thedomainnamesysteminthe80sandtheWorldWideWeb-nowthesecondmostpopularapplicationbehinde-mail-in1990.TheInternetexpandedbeyonditsinitialmilitaryandeducationaldomainintobusinessesandhomesaroundtheworld.Today,CrockercontinuesworkontheInternet,designingbettertoolsforcollaboration.AndassecuritychairmanfortheInternet#39;skeyoversightbody,heistryingtodefendthecoreaddressingsystemfromoutsidethreats.HeacknowledgestheInternethehelpedbuildisfarfromfinished,andchangesareinstoretomeetgrowingdemandsformultimedia.Networkprovidersnowmakeonlybesteffortsatdeliveringdatapackets,andCrockersaidbetterguaranteesareneededtopreventtheskipsandstuttersnowcommonwithvideo.Cerf,nowatMCIInc.,saidhewishedhecouldhavedesignedtheInternetwithsecuritybuilt-in.MicrosoftCorp.,YahooInc.andAmericaOnlineInc.,amongothers,arecurrentlytryingtoretrofitthenetworksoe-mailsenderscanbeauthenticated-awaytocutdownonjunkmessagessentusingspoofedaddresses.Manyfeaturesbeingdevelopedtodaywouldn#39;thavebeenpossibleatbirthgiventheslower2.DigitalCertificates DigitalcertificatesaredatafilesusedtoestablishtheidentityofpeopleandelectronicassetsontheInternet.Theyallowforsecure,encryptedonlinecommunicationandareoftenusedtoprotectonlinetransactions.Digitalcertificatesareissuedbyatrustedthirdpartyknownasacertificationauthority(CA).TheCAvalidatestheidentityofacertificateholderand“signs”thecertificatetoattestthatithasntbeenforgedoralteredinanyway.NewUsesForDigitalCertificatesDigitalcertificatesarenowbeingusedtoprovidesecurityandvalidationforwirelessconnections,andhardwaremanufacturersareoneofthelatestgroupstousethem.Notlongago,VeriSignInc.announceditsCableModemAuthenticationServices,whichallowhardwaremanufacturerstoembeddigitalcertificatesintocablemodemstohelppreventthepiratingofbroadbandservicesthroughdevicecloning.UsingVeriSignsoftware,hardwaremakerscangeneratecryptographickeysandcorrespondingdigitalcertificatesthatmanufacturersorcableserviceproviderscanusetoautomaticallyidentifyindividualmodems.Thisast-mileauthenticationnotonlyprotectsthevalueofexistingcontentandservicesbutalsopositionscablesystemoperatorstobringabroadnewrangeofcontent,applicationsandvalue-addedservicestomarket.WhenacertificateisdigitallysignedbyaCA,itsownercanuseitasanelectronicpassporttoprovehisidentity.ItcanbepresentedtoWebsites,networksorindividualsthatrequiresecureaccess.Identifyinginformationembeddedinthecertificateincludestheholdersnameande-mailaddress,thenameoftheCA,aserialnumberandanyactivationorexpirationdataforthecertificate.WhenausersidentityisverifiedbytheCA,thecertificateusestheholderspublicencryptionkeytoprotectthisdata.PublickeysarealsoemployedbycertificatesthataWebserverusestoconfirmtheauthenticityofaWebsiteforausersbrowser.WhenauserwantstosendconfidentialinformationtoaWebserver,suchasacredit-cardnumberforanonlinetransaction,thebrowserwillaccessthepublickeyintheserversdigitalcertificatetoverifyitsidentity.RoleofPublic-KeyCryptographyThepublickeyisonehalfofapairofkeysusedinpublic-keycryptography,whichprovidesthefoundationfordigitalcertificates.Public-keycryptographyusesmatchedpublicandprivatekeysforencryptionanddecryption.Thesekeyshaveanumericalvaluethatsusedbyanalgorithmtoscrambleinformationandmakeitreadableonlytouserswiththecorrespondingdecryptionkey.Apersonspublickeyisusedbyotherstoencryptinformationmeantonlyforthatperson.Whenhereceivestheinformation,heuseshiscorrespondingprivatekey,whichiskeptsecret,todecryptthedata.Aperson#39;spublickeycanbedistributedwithoutdamagingtheprivatekey.AWebserverusingadigitalcertificatecanuseitsprivatekeytomakesurethatonlyitcandecryptconfidentialinformationsenttoitovertheInternet.TheWebserverscertificateisvalidatedbyaself-signedCAcertificatethatidentifiestheissuingCA.CAcertificatesarepreinstalledonmostmajorWebbrowsers,includingMicrosoftInternetExplorerandNetscapeNavigator.TheCAcertificatetellsuserswhethertheycantrusttheWebservercertificatewhenitspresentedtothebrowser.IfthevalidityoftheWebservercertificateisaffirmed,thecertificatespublickeyisusedtosecureinformationfortheserverusingSecureSocketsLayer(SSL)technology.DigitalcertificatesareusedbytheSSLsecurityprotocoltocreateasecure“pipe”betweentwopartiesthatseekconfidentialcommunication.SSLisusedinmostmajorWebbrowsersandcommercialWebservers.3.DigitalWallets-AdigitalwalletissoftwarethatenablesuserstopayforgoodsontheWebItholdscredit-cardnumbersandotherpersonalinformationsuchasashippingaddressOnceentered，thedataautomaticallypopulatesorderfieldsatmerchantsites-Whenusingadigitalwallet，consumersdontneedtofilloutorderformsoneachsitewhentheypurchaseanitembecausetheinformationhasalreadybeenstoredandisautomaticallyupdatedandenteredintotheorderfieldsacrossmerchantsitesConsumersalsobenefitwhenusingdigitalwalletsbecausetheirinformationisencryptedorprotectedbyaprivatesoftwarecodeAndmerchantsbenefitbyreceivingprotectionagainstfraud-Digitalwalletsareavailabletoconsumersfreeofcharge，andtheyrefairlyeasytoobtainForexample，whenaconsumermakesapurchaseatamerchantsitethatssetuptohandleserver-sidedigitalwallets，hetypeshisnameandpaymentandshippinginformationintothemerchantsownformAttheendofthepurchase，oneconsumerisaskedtosignupforawalletofhischoicebyenteringausernameandpasswordforfuturepurchasesUserscanalsoacquirewalletsatawalletvendorssite-Althoughawalletisfreeforconsumers，vendorschargemerchantsforwallets-Digitalwalletscomeintwomaintypes:client-sideandserver-sideWithinthosedivisionsarewalletsthatworkonlyonspecificmerchantsitesandthosethataremerchantagnostic-Client-baseddigitalwallets，theolderofthetwotypes，arefallingbythewayside，accordingtoanalysts，becausetheyrequireuserstodownloadandinstallsoftwareAuserdownloadsthewalletapplicationandinputspaymentandmailinginformationAtthatpoint，theinformationissecuredandencryptedontheusersharddriveTheuserretainscontrolofhiscreditcardandpersonalinformationlocally-Withaserver-basedwallet，auserfillsouthispersonalinformation，andacookieisautomaticallydownloaded（Acookieisatextfilethatcontainsinformationabouttheuser）Inthisscenario，theconsumerinformationresidesontheserverofafinancialinstitutionoradigitalwalletvendorratherthanontheusersPC-Server-sidewalletsprovideassuranceagainstmerchantfraudbecausetheyusecertificatestoverifytheidentityofallpartiesWhenapartymakesatransaction，itpresentsitscertificatetotheotherpartiesinvolvedAcertificateisanattachmenttoanelectronicmessageusedtoverifytheidentityofthepartyandtoprovidethereceiverwiththemeanstoencodeareply-Furthermore，thecardholderssensitivedataistypicallyhousedatafinancialinstitution，sotheresanextrasenseofsecuritybecausefinancialenvironmentsgenerallyprovidethehighestdegreeofsecurity-Buteventhoughwalletsprovideeasyshoppingonline，adoptionhasntbeenwidespread-Standardsarepivotaltothesuccessofdigitalwallets-Lastmonth，majorvendors，includingMicrosoftCorp，SunMicrosystemsIncandAmericaOnlineIncannouncedtheirendorsementofanewstandardcalledEMCL，orE-CommerceModelingLanguage，togiveWebmerchantsastandardizedwaytocollectelectronicdataforshipping，billingandpayment4.GridStorageDefinition:Gridstorage,analogoustogridcomputing,isanewmodelfordeployingandmanagingstoragedistributedacrossmultiplesystemsandnetworks,makingefficientuseofavailablestoragecapacitywithoutrequiringalarge,centralizedswitchingsystem.Agridis,infact,ameshednetworkinwhichnosinglecentralizedswitchorhubcontrolsrouting.Gridsofferalmostunlimitedscalabilityinsizeandperformancebecausetheyarentconstrainedbytheneedforever-largercentralswitches.Gridnetworksthusreducecomponentcostsandproduceareliableandresilientstructure.Applyingthegridconcepttoacomputernetworkletsusharnessavailablebutunusedresourcesbydynamicallyallocatinganddeallocatingcapacity,bandwidthandprocessingamongnumerousdistributedcomputers.Acomputinggridcanspanlocations,organizations,machinearchitecturesandsoftwareboundaries,offeringpower,collaborationandinformationaccesstoconnectedusers.UniversitiesandresearchfacilitiesareusinggridstobuildwhatamountstosupercomputercapabilityfromPCs,MacintoshesandLinuxboxes.Aftergridcomputingcameintobeing,itwasonlyamatteroftimebeforeasimilarmodelwouldWhatIsGridStorage? Basedoncurrentandproposedproducts,itappearsthatagridstoragesystemshouldincludethefollowing:Modularstoragearrays:ThesesystemsareconnectedacrossastoragenetworkusingserialATAdisks.Thesystemscanbeblock-orientedstoragearraysornetwork-attachedstoragegatewaysandservers.Commonvirtualizationlayer:Storagemustbeorganizedasasinglelogicalpoolofresourcesavailabletousers.Dataredundancyandavailability:Multiplecopiesofdatashouldexistacrossnodesinthegrid,creatingredundantdataaccessandavailabilityincaseofacomponentfa