完整版毕业设计外文文献翻译69267082.docx

完整版毕业设计外文文献翻译69267082.docx

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完整版毕业设计外文文献翻译69267082

毕业设计（论文）

外文文献翻译

专业

计算机科学与技术

学生姓名

班级

学号

指导教师

信息工程学院

1、外文文献

TheHistoryoftheInternet

TheBeginning-ARPAnet

TheInternetstartedasaprojectbytheUSgovernment.Theobjectoftheprojectwastocreateameansofcommunicationsbetweenlongdistancepoints,intheeventofanationwideemergencyor,morespecifically,nuclearwar.TheprojectwascalledARPAnet,anditiswhattheInternetstartedas.Fundedspecificallyformilitarycommunication,theengineersresponsibleforARPANet"Internet."

Bydefinition,an'Internet'isfourormorecomputersconnectedbyanetwork.

ARPAnetachieveditsnetworkbyusingaprotocolcalledTCPIP.Thebasicsaroundthisprotocolwasthatifinformationsentoveranetworkfailedtogetthroughononeroute,itwouldfindanotherroutetoworkwith,aswellasestablishingameansforonecomputerto"talk"toanothercomputer,regardlessofwhetheritwasaPCoraMacintosh.

Bythe80'sARPAnet,justyearsawayfrombecomingthemorewellknownInternet,itsnetwork.Bytheyear1984,ititsnetwork.

In1986ARPAnet（supposedly）shutdown,butonlytheorganizationshut

down,andtheexistingnetworksstillexistedbetweenthemorethan1000

computers.ItshutdownduetoafailiedlinkupwithNSF,whowantedto

connectits5countywidesupercomputersintoARPAnet.

WiththefundingofNSF,new1988.Bythattime,therewere28,174computersonthe（bythendecided）Internet.In1989therewere80,000computersonit.By1989,therewere.

Anothernetworkwasbuilttosupporttheincrediblenumberofpeople

joining.Itwasconstructedin1992.

Today-TheInternet

Today,theInternettheline'toexperiencethewealthofinformationoftheInternet.MillionsofpeoplenowusetheInternet,andit'spredictedthatbytheyear2003everysinglepersonontheplanetwillourtimeandera,andisevolvingsoquicklyitsvirtualInternetenvironments.

TheInternetisnota'thing'itself.TheInternetcannotjust"crash."Itfunctionsthesamewayasthetelephonesystem,onlythereisnoInternetcompanythatrunstheInternet.

TheInternetisacollectionofmillioinsofcomputersthatareallconnectedtoeachother,orofficenetwork,onlyitthingabout.HowdoesacomputerinHoustonknowacomputerinTokyotoviewawebpage?

Internetcommunication,communicationamongcomputersconnectedtotheInternet,isbasedonalanguage.ThislanguageiscalledTCPIP.TCPIPestablishesalanguageforacomputertoaccessandtransmitdataovertheInternetsystem.

ButTCPIPassumesthatthereisaphysicalconnecetionbetweenonecomputerandanother.Thisisnotusuallythecase.Therewouldthatisrequireedisestablishedbywayofmodems,phonelines,andothermodemcableconnections（likecablemodemsorDSL）.Modemsoncomputersreadandtransmitdataoverestablishedlines,whichcouldbephonelinesordatalines.Theactual.

Toexplainthisbetter,let'slookatInternetServiceProvider（ISP）.TheISPmightinturnbeconnectedtoanotherISP,orastraightconnectionintotheInternetbackbone.

2.TheuserlaunchesawebbrowserlikeNetscapeorInternetExplorerandtypesinaninternetlocationtogoto.

3.Here'swherethetrickypartcomesin.First,thecomputersendsdataaboutit'sdatarequesttoarouter.Arouterisaveryofroutersintheworldmakewhatiscalleda"backbone,"onwhichallthedataontheInternetistransferred.Thebackbonepresentlyoperatesataspeedofseveralgigabytesper-second.Suchaspeedcomparedtoanormalmodemislikecomparingthetotheice-cube.

Routerssimilarlytoenvelopes.So,whentherequestforthewebpagegoesthrough,itusesTCPIPprotocolstotelltherouterwhattodowiththedata,whereit'sgoing,andoverallwheretheuserwantstogo.

4.Theroutersendsthesepacketstootherrouters,eventuallyleadingtothetargetcomputer.It'slikewhisperdownthelane（onlytheinformationremainsintact）.

5.Whentheinformationreachesthetargetwebserver,thewebserverthenbeginstosendthewebpageback.Awebserveristhecomputerwherethewebpageisstoredthatisrunningaprogramthatpackets,sentthroughrouters,andarriveattheuserscomputerwheretheusercanviewthewebpageonceitisassembled.

Thepacketswhichcontainthedataalsocontainspecialinformationthatletsroutersandothercomputersknowtherightorder.

Withmillionsofwebpages,andmillionsofusers,usingtheInternetisnotalwayseasyforabeginninguser,especiallyforsomeonewhoisnotentirelycomfortalewithusingcomputers.BelowyoucanfindtipstricksandservicesoftheInternet.

Beforeyouaccesswebpages,youmustthesoftwaretheyusuallygivetocustomers;you.ThefactthatyouareviewingthispagemeansthatyoubefoundatandMSIEcanbefoundat

Thefactthatyou'rereadingthisrightnowmeansthatyouofinstructions（likeifitremarkmadebynewweb-users.

Sometimeswebsiteserroronawebsiteisnottheuser'sfault,ofcourse.

A404errormeansthatthepageyoutriedtogotodoesnotexist.Thiscouldbebecausethesiteisstillbeingconstructedandthepagecreatedyet,orbecausethesiteauthormadeatypointhepage.There'snothingmuchtodoabouta404errorexceptfore-mailingthesiteadministrator（ofthepageyouwantedtogoto）antellingtheJavascriptcodeofawebsite.NotallwebsitesutilizeJavascript,butmanydo.JavascriptisdifferentfromJava,andmostbrowsersnowsupportJavascript.Ifyouareusinganoldversionofawebbrowser（Netscape3.0forexample）,youmightgetJavascripterrorsbecausesitesutilizeJavascriptversionsthatyourbrowserdoesnotsupport.So,youcantrygettinganewerversionofyourwebbrowser.

E-mailstandsforElectronicMail,andthat'swhatitis.E-mailenablespeopletosendletters,andevenfilesandpicturestoeachother.

Tousee-mail,youmuste-mailclient,whichisjustlikeapersonalpostoffice,sinceitretrievesandstorese-mail.

Secondly,youmuste-mailaccount.MostInternetServiceProvidersprovidefreee-mailaccount（s）forfree.Someservicesofferfreee-mail,likeHotmail,andGeocities.

Afterconfiguringyoure-mailclientwithyourPOP3andSMTPserveraddress（youre-mailproviderwillgiveyouthatinformation）,youarereadytoreceivemail.

Anattachmentisafilesentinaletter.Ifsomeonesendsyouanattachmentandyoudon'tknowwhoitis,don'trunthefile,ever.Itcouldbeavirusorsomeotherkindofnastyprograms.Youcan'tgetavirusjustbyreadinge-mail,you'llputatextgraphic,yourbusinessinformation,anythingyouwant.

ImaginethatacomputerontheInternetisanislandinthesea.Theseaisfilledwithmillionsofislands.ThisistheInternet.Imagineanislandcommunicateswithotherislandbysendingshipstootherislandsandreceivingships.TheislandtheInternetanetwork（ortheInternet）.Thismethodissimilartotheislandoceansymbolismabove.

Telnetreferstoaccessingportsonaserverdirectlywithatextconnection.AlmosteverykindofInternetfunction,likeaccessingwebpages,"chatting,"ande-mailingisdoneoveraTelnetconnection.

TelnettingrequiresaTelnetclient.AtelnetprogramcomeswiththeWindowssystem,soWindowsuserscanaccesstelnetbytypingin"telnet"（withoutthe"'s）intherundialog.Linux,chatdaemon）canbeaccessedviatelnet,althoughtheyarenotusuallymeanttobeaccessedinsuchamanner.Forinstance,itispossibletoconnectdirectlytoamailserverandcheckyourmailbyinterfacingwiththee-mailserversoftware,butit'seasiertouseane-mailclient（ofcourse）.

TherearemillionsofWebPagesthatcomefromallovertheworld,yetdatabaseofwebsites.Forinstance,ifyouwantedtofindawebsiteondogs,you'dsearchfor"dog"or"dogs"or"doginformation."Hereareafewsearch-engines.

1.Altavista（

3.Excite（possiblyfind.ThismeansthatasearchenginecanliterallymapoutasmuchoftheInternetasit'sowntimeandspeedallowsfor.

AnindexedcollectionusesYahoo'ssite.YoucanclickonComputers&theInternet.ThenyoucanclickonHardware.ThenyoucanclickonModems,etc.,andalongthewaythroughsections,therearesitesavailablewhichrelatetowhatsectionyou'rein.

Metasearchsearchesmanysearchenginesatthesametime,findingthetopchoicesfromabout10searchengines,makingsearchingalotmoreeffective.

Onceyouareabletousesearchengines,youcaneffectivelyfindthepagesyouwant.

Withthearrivalofnetworkingandmultiusersystems,securityonthemindofsystemdevelopersandsystemoperators.SincethedawnofAT&Tanditsphonenetwork,knownbymany,.Whyshouldyoubecarefulwhilemakingpurchasesviaawebsite?

Let'slookattoawebpage.Lookssafe,right?

Notnecessarily.Astheusersubmitstheinformation,itisbeingstreamedthroughaseriesofcomputersthatmakeuptheInternetbackbone.Theinformationisinlittlechunks,inpackagescalledpackets.Here'stheproblem:

Whiletheinformationisbeingtransferredthroughthisbigbackbone,whatispreventinga".Therearemethodsofenforcingsecurity,likepasswordprotection,anmostimportantly,encryption.

Encryptionmeansscramblingdataintoacodethatcanonlybeunscrambledonthe"otherend."Browser'slikeNetscapeCommunicatorandInternetExplorerfeatureencryptionsupportformakingon-linetransfers.Someencryptionsworkbetterthanothers.ThemostadvancedencryptionsystemiscalledDES（DataEncryptionStandard）,anditwasadoptedbytheUSDefenseDepartmentbecauseitwasdeemedsodifficultto'crack'thattheyconsidereditasecurityriskifitwouldfallintoanothercountriestounlockanentiredocument.Thepr