网络工程局域网中英文对照外文翻译文献Word文档格式.docx
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网络工程局域网中英文对照外文翻译文献Word文档格式.docx
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网络工程局域网中英文对照外文翻译文献@#@中英文对照外文翻译@#@(文档含英文原文和中文翻译)@#@1.COMPUTERNETWORKS@#@DATECOMMUNICATIONS@#@Theendequipmentwhicheithergeneratesthedigitalinformationfortransmissionorusesthereceiveddigitaldatacanbecomputer,printers,keyboards,CRTs,andsoon.Thisequipmentgenerallymanipulatesdigitalinformationinternallyinwordunits—allthebitsthatmakeupawordinaparticularpieceofequipmentaretransferredinparallel.Digitaldata,whentransmitted,areinserialform.Paralleltransmissionofan8-bitwordrequireeightpairsoftransmissionlines—notatallcost-effective.Dataterminal(DTE)isageneralphraseencompassingallofthecircuitrynecessarytoperformparallel-to-serialandserial-to-parallelconversionsfortransmissionandreceptionrespectivelyandfordatalinkmanagement.TheUART(UniversalAsynchronousReceiver/Transmitter)andUSART(UniversalAsynchronous/AsynchronousReceiver/Transmitter)arethedevicesthatperformtheparallel-to-serialandserial-to-parallelconversions.TheprimaryDTEincludesalinecontrolunit(LCUorLinCo)whichcontrolstheflowofinformationinamultipointdatalinksystem.Astationcontroller(STACO)isthecorrespondingthatbelongedtothesubscriberinadatalinksystem.BetweentheDTEs,startingwiththemodems,wascommunicationsequipmentownedandmaintainedbyTelcoproperty.@#@Datacommunicationsequipment(DCE)acceptstheserialdatastreamfromtheDTEandconvertsittosomeformofanalogsignalsuitablefortransmissiononvoice-gradelined.Atthereceiveend,theDCEperformsthereversefunctionofconvertingthereceivedanalogsignaltoaserialdigitaldatastream.ThesimplestformofDCEisamodem(modulator/demodulator)ordataset.Atthetransmitend,themodemcanbeconsideredaformofdigital-to-analogconverter,whileatthereceiveend,itcanconsideredaformofanalog-to-digitalconverter.Themostcommonofmodulationbymodemsarefrequencyshiftkeying(FSK),phaseshiftkeying(PSK),andquadratureamplitudemodulation(QAM).Thisisatypicallydatatransmissionmodeusingtheanalogtelephonelines.Ifyoutransmitdatabydigitalchannel(sometimesitiscalled“DigitalT-carrier”),apulseCodeModulation(PCM)equipmentmustbeused.Amicrowavetransmissionsystemcanalsobeusedforthedatacommunication.Finally,youcanusethesatellitecommunicationsystemfordatatransmission.@#@IfthecablesandsignallevelsusedtointerconnecttheDTEandDCEwereleftunregulated,thevariationsgeneratedwouldprobablybeproportionaltothenumberofmanufacturers.ElectronicsindustriesAssociation(EIA),anorganizationofmanufactureswithestablishingtheDTEandmodem.Thisisa25-pincablewhosepinshavedesignatedfunctionsandspecifiedsignallevels.TheRS-232Cisanticipatedtobereplacedbyanupdatestandard.@#@2.ARCHITECTUREOFCOMPUTERNETWORKS@#@Computernetworkisacomplexconsistingoftwoormoreconnedcomputingunits,itisusedforthepurposeofdatacommunicationandresourceresourcesharing.Designofanetworkanditslogicalstructureshouldcomplywithasetofdesignprinciples,includingtheorganizationoffunctionsandthedescriptionofdataformatsandprocedure.Thisisthenetworkarchitectureandsocalledasasetoflayersandprotocols,becausethearchitectureisalayer-based.@#@Inthenexttwosectionswewilldiscusstwoimportantnetworkarchitectures,theOSIreferencemodelandtheTCP/IPreferencemodel.@#@1.TheOSIReferenceModel@#@TheOSImodelisshowninFig.14-2(minusthephysicalmedium).ThismodelisbasedonaproposaldevelopedbytheInternationalStandardsOrganizations(OSI)asthefirststeptowardinternationalstandardizationoftheprotocolsusedinthevariouslayers.ThemodeliscalledtheISOOSI(OpenSystemInterconnection)ReferenceModelbecauseitdealswithconnectingopensystems--thatis,systemsthatareopenforcommunicationwithothersystems,WewillusuallyjustcallittheOSImodelforshort.@#@TheOSImodelhassevenhassevenlayers.NotethattheOSImodelitselfisnotanetworkarchitecturebecauseitdoesnotspecifytheexactservicesandprotocolstobeusedineachlayer.Itjusttellswhateachlayershoulddo.However,However,ISOhasalsoproducedstandardsforallthelayers,althoughthesearenotpartofthereferencemodelitself.Eachonehasbeenpublishedasaseparateinternationalstandard.@#@2.TheTCP/IPReferenceModel@#@TheTCP/IPreferencemodelisanearlytransportprotocolwhichwasdesignedbytheUSDepartmentofDefence(DOD)aroundin1978.ItisoftenclaimedthatitgaverisetheOSI“connectionless”modeofoperation.TCP/IPisstillusedextensivelyandiscalledasaindustrialstandardofinternetworkinfact,TCP/IPhastwoparts:
@#@TCPandIP.TCPmeansitisonthetransportlayerandIPmeansitisonthenetworklayerseparately.@#@1.Therearetwoend-to-en
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