网络工程局域网中英文对照外文翻译文献.docx

网络工程局域网中英文对照外文翻译文献.docx

《网络工程局域网中英文对照外文翻译文献.docx》由会员分享，可在线阅读，更多相关《网络工程局域网中英文对照外文翻译文献.docx（8页珍藏版）》请在冰豆网上搜索。

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