网络工程局域网中英文对照外文翻译文献Word文档格式.docx

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