外文翻译--网络的诞生.doc

BirthoftheNetTheInternethashadarelativelybrief,butexplosivehistorysofar.Itgrewoutofanexperimentbeguninthe1960sbytheU.S.DepartmentofDefense.TheDoDwantedtocreateacomputernetworkthatwouldcontinuetofunctionintheeventofadisaster,suchasanuclearwar.Ifpartofthenetworkweredamagedordestroyed,therestofthesystemstillhadtowork.ThatnetworkwasARPANET,whichlinkedU.S.scientificandacademicresearchers.ItwastheforerunneroftodaysInternet.In1985,theNationalScienceFoundation(NSF)createdNSFNET,aseriesofnetworksforresearchandeducationcommunication.BasedonARPANETprotocols,theNSFNETcreatedanationalbackboneservice,providedfreetoanyU.S.researchandeducationalinstitution.Atthesametime,regionalnetworkswerecreatedtolinkindividualinstitutionswiththenationalbackboneservice.NSFNETgrewrapidlyaspeoplediscovereditspotential,andasnewsoftwareapplicationswerecreatedtomakeaccesseasier.CorporationssuchasSprintandMCIbegantobuildtheirownnetworks,whichtheylinkedtoNSFNET.AscommercialfirmsandotherregionalnetworkprovidershavetakenovertheoperationofthemajorInternetarteries,NSFhaswithdrawnfromthebackbonebusiness.NSFalsocoordinatedaservicecalledInterNIC,whichregisteredalladdressesontheInternetsothatdatacouldberoutedtotherightsystem.ThisservicehasnowbeentakenoverbyNetworkSolutions,Inc.,incooperationwithNSF.HowtheWebWorksTheWorldWideWeb,thegraphicalportionoftheInternet,isthemostpopularpartoftheInternetbyfar.OnceyouspendtimeontheWeb,youwillbegintofeellikethereisnolimittowhatyoucandiscover.TheWeballowsrichanddiversecommunicationbydisplayingtext,graphics,animation,photos,soundandvideo.Sojustwhatisthismiraculouscreation?TheWebphysicallyconsistsofyourpersonalcomputer,webbrowsersoftware,aconnectiontoanInternetserviceprovider,computerscalledserversthathostdigitaldataandroutersandswitchestodirecttheflowofinformation.TheWebisknownasaclient-serversystem.Yourcomputeristheclient；theremotecomputersthatstoreelectronicfilesaretheservers.Hereshowitworks:LetssayyouwanttopayavisittothetheLouvremuseumwebsite.FirstyouentertheaddressorURLofthewebsiteinyourwebbrowser(moreaboutthisshortly).ThenyourbrowserrequeststhewebpagefromthewebserverthathoststheLouvressite.TheLouvresserversendsthedataovertheInternettoyourcomputer.Yourwebbrowserinterpretsthedata,displayingitonyourcomputerscreen.TheLouvreswebsitealsohaslinkstothesitesofothermuseums,suchastheVaticanMuseum.Whenyouclickyourmouseonalink,youaccessthewebserverfortheVaticanMuseum.The"glue"thatholdstheWebtogetheriscalledhypertextandhyperlinks.ThisfeatureallowelectronicfilesontheWebtobelinkedsoyoucaneasilyjumpbetweenthem.OntheWeb,younavigatethroughpagesofinformationbasedonwhatinterestsyouatthatparticularmoment,commonlyknownasbrowsingorsurfingtheNet.ToaccesstheWebyouneedwebbrowsersoftware,suchasNetscapeNavigatororMicrosoftInternetExplorer.HowdoesyourwebbrowserdistinguishbetweenwebpagesandotherfilesontheInternet?WebpagesarewritteninacomputerlanguagecalledHypertextMarkupLanguageorHTML.SomeWebHistoryTheWorldWideWeb(WWW)wasoriginallydevelopedin1990atCERN,theEuropeanLaboratoryforParticlePhysics.ItisnowmanagedbyTheWorldWideWebConsortium,alsoknownastheWorldWideWebInitiative.TheWWWConsortiumisfundedbyalargenumberofcorporatemembers,includingAT&T,AdobeSystems,Inc.,MicrosoftCorporationandSunMicrosystems,Inc.ItspurposeistopromotethegrowthoftheWebbydevelopingtechnicalspecificationsandreferencesoftwarethatwillbefreelyavailabletoeveryone.TheConsortiumisrunbyMITwithINRIA(TheFrenchNationalInstituteforResearchinComputerScience)actingasEuropeanhost,incollaborationwithCERN.TheNationalCenterforSupercomputingApplications(NCSA)attheUniversityofIllinoisatUrbana-Champaign,wasinstrumentalinthedevelopmentofearlygraphicalsoftwareutilizingtheWorldWideWebfeaturescreatedbyCERN.NCSAfocusesonimprovingtheproductivityofresearchersbyprovidingsoftwareforscientificmodeling,analysis,andvisualization.TheWorldWideWebwasanobviouswaytofulfillthatmission.NCSAMosaic,oneoftheearliestwebbrowsers,wasdistributedfreetothepublic.ItleddirectlytothephenomenalgrowthoftheWorldWideWeb.UnderstandingWebAddressesYoucanthinkoftheWorldWideWebasanetworkofelectronicfilesstoredoncomputersallaroundtheworld.Hypertextlinkstheseresourcestogether.UniformResourceLocatorsorURLsaretheaddressesusedtolocatethesefiles.TheinformationcontainedinaURLgivesyoutheabilitytojumpfromonewebpagetoanotherwithjustaclickofyourmouse.WhenyoutypeaURLintoyourbrowserorclickonahypertextlink,yourbrowserissendingarequesttoaremotecomputertodownloadafile.WhatdoesatypicalURLlooklike?Herearesomeexamples:http:/english.chinaschool.net/Thehomepageforstudyenglish.ftp:/rtfm.mit.edu/pub/AdirectoryoffilesatMIT*availablefordownloading.news:rec.gardens.rosesAnewsgrouponrosegardening.ThefirstpartofaURL(beforethetwoslashes*tellsyouthetypeofresourceormethodofaccessatthataddress.Forexample:http-ahypertextdocumentordirectorygopher-agopherdocumentormenuftp-afileavailablefordownloadingoradirectoryofsuchfilesnews-anewsgrouptelnet-acomputersystemthatyoucanlogintoovertheInternetWAIS*-adatabaseordocumentinaWideAreaInformationSearchdatabasefile-afilelocatedonalocaldrive(yourharddrive)Thesecondpartistypicallytheaddressofthecomputerwherethedataorserviceislocated.Additionalpartsmayspecifythenamesoffiles,theporttoconnectto,orthetexttosearchforinadatabase.YoucanentertheURLofasitebytypingitintotheLocationbarofyourwebbrowser,justunderthetoolbar.MostbrowsersrecordURLsthatyouwanttouseagain,byaddingthemtoaspecialmenu.InNetscapeNavigator,itscalledBookmarks.InMicrosoftExplorer,itscalledFavorites.OnceyouaddaURLtoyourlist,youcanreturntothatwebpagesimplybyclickingonthenameinyourlist,insteadofretypingtheentireURL.MostoftheURLsyouwillbeusingstartwithhttpwhichstandsforHypertextTransferProtocol*.httpisthemethodbywhichHTMLfilesaretransferredovertheWeb.HerearesomeotherimportantthingstoknowaboutURLs:AURLusuallyhasnospaces.AURLalwaysusesforwardslashes(/).IfyouenteraURLincorrectly,yourbrowserwillnotbeabletolocatethesiteorresourceyouwant.Shouldyougetanerrormessageorthewrongsite,makesureyoutypedtheaddresscorrectly.YoucanfindtheURLbehindanylinkbypassingyourmousecursoroverthelink.ThepointerwillturnintoahandandtheURLwillappearinthebrowsersstatusbar,usuallylocatedatthebottomofyourscreen.DomainNamesWhenyouthinkoftheInternet,youprobablythinkof".com."JustwhatdothosethreelettersattheendofaWorldWideWebaddressmean?EverycomputerthathostsdataontheInternethasauniquenumericaladdress.Forexample,thenumericaladdressfortheWhiteHouseis198.137.240.100.Butsincefewpeoplewanttorememberlongstringsofnumbers,theDomainNameSystem(DNS)*wasdeveloped.DNS,acriticalpartoftheInternetstechnicalinfrastructure*,correlates*anumericaladdresstoaword.ToaccesstheWhiteHousewebsite,youcouldtypeitsnumberintotheaddressboxofyourwebbrowser.Butmostpeopleprefertouse"www.whitehouse.gov."Inthiscase,thedomainnameiswhitehouse.gov.Ingeneral,thethree-letterdomainnamesuffix*isknownasagenerictop-leveldomainanddescribesthetypeoforganization.Inthelastfewyears,thelineshavesomewhatblurred*betweenthesecategories.com-business(commercial).edu-educational.org-non-profit.mil-military.net-networkprovider.gov-governmentAdomainnamealwayshastwoormorepartsseparatedbydotsandtypicallyconsistsofsomeformofanorganizationsnameandthethree-lettersuffix.Forexample,thedomainnameforIBMis"ibm.com"；theUnitedNationsis"un.org."Ifadomainnameisavailable,andprovideditdoesnotinfringe*onanexistingtrademark,anyonecanregisterthenamefor$35ayearthroughNetworkSolutions,Inc.,whichisauthorizedtoregister.com,.netand.orgdomains.Youcanusetheboxbelowtoseeifanameisaavailable.Dontbesurprisedifthe.comnameyouwantisalreadytaken,however.Oftheover8milliondomainnames,85%are.comdomains.ICANN,theInternetCorporationforAssignedNamesandNumbers,managestheDomainNameSystem.Asofthiswriting,thereareplanstoaddadditionaltop-leveldomains,suchas.weband.store.Whenthatwillactuallyhappenisanybodysguess.Tocheckfor,orregisteradomainname,typeitintothesearchbox.Itshouldtakethisform:myname.comInadditiontothegenerictop-leveldomains,244nationaltop-leveldomainswereestablishedforcountriesandterritories*,forexample:.au-Australia.ca-Canada.fr-France.de-Germany.uk-UnitedKingdomForUS$275pername,youcanalsoregisteraninternationaldomainnamewithNetNames.Beawarethatsomecountrieshaverestrictionsforregisteringnames.Ifyouplantoregisteryourowndomainname,whetheritsa.comornot,keepthesetipsinmind:Theshorterthename,thebetter.(Butitshouldreflectyourfamilyname,interestorbusiness.)Thenameshouldbeeasytoremember.Itshouldbeeasytotypewithoutmakingmistakes.Remember,theInternetisglobal.Ideally,adomainnamewill"read"inalanguageotherthanEnglish.