计算机网络专业英语 习题答案K2

Lessons2NetworkClassificationModule3ConsolidationExercise（巩固练习）I.Answerthefollowingquestionsaccordingtothepassage.1.Whatisoneimportantcriterionforclassifyingnetworks?2.WhatdoyouknowaboutthefirstversionofEthernet?3.WhywereswitchesintroducedtoreplacehubsinEthernet-basednetworks?4.WhatstandardsaremostmodernWLANsbasedon?5.Whatbasicmodesofoperationdoesthe

IEEE802.11

have?6.Whydidthe802.11designersalsoincludeencryptionmechanismslike

WiredEquivalentPrivacyandWi-FiProtectedAccess?7.WhatcausesablurringofthedistinctionbetweenLANsandWANs?8.WhydoprivateorganizationslikebigsoftwarecompanieshavetheirownWANsconstructednowadays?II.GivethemeaningofthefollowingabbreviatedtermsbothinEnglishandinChinese.PAN CSMA/CDMAN WPAUTPLANWLANRFIDWEP WANIII.TranslatethefollowingsentencesintoChinese.Tohelptheseusers,somecompaniesgottogethertodesignashort-rangewirelessnetworkcalledBluetoothtoconnectthesecomponentswithoutwires.Knowingthisboundmakesitpossibletousecertainkindsofdesignsthatwouldnototherwisebepossible.Ethernetwasdesignedtoaccommodatemultiplecomputersthatwereinterconnectedonasharedbustopology.AsignificantdevelopmentthatenhancedLANperformancewastheintroductionofswitchestoreplacehubsinEthernet-basednetworks.WirelessLANshavebecomepopularinthehomeduetoeaseofinstallationanduse,andincommercialcomplexesofferwirelessaccesstotheircustomers,oftenforfree.

Ininfrastructuremode,mobileunitscommunicatethroughan

accesspoint

thatservesasabridgetoothernetworks(suchas

Internet

or

LAN).Manyaccesspointswillalsooffer

Wi-FiProtectedSetup,aquick(butnowinsecure)methodofjoininganewdevicetoanencryptednetwork.AlldatathatistransmittedontheInternetisalwayslabeledwiththedestinationaddresswhichisanumericalnameassignedtoeverycomputerconnectedonthenetwork.Key

to

the

ExercisesLesson2Module3Practice&Consolidation（练习巩固）I.Answerthefollowingquestionsaccordingtothepassage.1.Whatisoneimportantcriterionforclassifyingnetworks?Oneimportantcriterionforclassifyingnetworksistheirscale(physicalsize).2.WhatdoyouknowaboutthefirstversionofEthernet?ThefirstversionofEthernetincorporatedamediaaccessmethodknownasCarrierSenseMultipleAccesswithCollisionDetection(CSMA/CD).CSMA/CDmanagedtheproblemsthatarosewhenmultipledevicesattemptedtocommunicateoverasharedphysicalmedium.3.WhywereswitchesintroducedtoreplacehubsinEthernet-basednetworks?TheintroductionofswitchestoreplacehubsinEthernet-basednetworkshelpcontroltheflowofdatabyisolatingeachportandsendingaframeonlytoitsproperdestination(ifthedestinationisknown),ratherthansendeveryframetoeverydevice.4.WhatstandardsaremostmodernWLANsbasedon?MostmodernWLANsarebasedon

IEEE802.11

standards,marketedunderthe

Wi-Fi

brandname.5.Whatbasicmodesofoperationdoesthe

IEEE802.11

have?The

IEEE802.11

hastwobasicmodesofoperation:

infrastructure

and

adhoc

mode.6.Whydidthe802.11designersalsoincludeencryptionmechanismslike

WiredEquivalentPrivacyandWi-FiProtectedAccess

?BecausewirelesscommunicationusesamoreopenmediumforcommunicationincomparisontowiredLANs,the802.11designersalsoincludedencryptionmechanismtosecurewirelesscomputernetworks.7.WhatcausesablurringofthedistinctionbetweenLANsandWANs?Theincreasedcablingdistancesenabledbytheuseoffiber-opticcableinEthernet-basednetworkshasresultedinablurringofthedistinctionbetweenLANsandWANs.8.WhydoprivateorganizationslikebigsoftwarecompanieshavetheirownWANsconstructednowadays?Nowadays,privateorganizationslikebigsoftwarecompanieshavetheirownWANsconstructed,becauseitmakestheirinternalcommunicationsimplerandmoresecure.II.GivethemeaningofthefollowingabbreviatedtermsbothinEnglishandinChinese.PAN:PersonalAreaNetwork个域网 CSMA/CD:CarrierSenseMultipleAccesswithCollisionDetection带冲突检测的载波监听多路访问 MAN:MetropolitanAreaNetwork城域网WPA:Wi-FiProtectedAccessWi-Fi保护接入UTP:UnshieldedTwistedPaired无屏蔽双绞线LAN:LocalAreaNetwork局域网WLAN:WirelessLocalAreaNetwork无线局域网RFID:RadioFrequencyIdentification无线射频识别WEP:WiredEquivalentPrivacy有线等效加密WAN:WideAreaNetwork广域网III.TranslatethefollowingsentencesintoChinese.1.Tohelptheseusers,somecompaniesgottogethertodesignashort-rangewirelessnetworkcalledBluetoothtoconnectthesecomponentswithoutwires.为帮助这些用户，有些公司共同设计了一个名为“蓝牙”的短程无线网络来无线连接这些部件。2.Knowingthisboundmakesitpossibletousecertainkindsofdesignsthatwouldnototherwisebepossible.知道该范围（指最长传输时间）就可以使用某些原本不可能使用的特殊设计。3．Ethernetwasdesignedtoaccommodatemultiplecomputersthatwereinterconnectedonasharedbustopology.设计以太网就是为了接入通过共享总线拓扑互连的多台计算机。4．AsignificantdevelopmentthatenhancedLANperformancewastheintroductionofswitchestoreplacehubsinEthernet-basednetworks.提高局域网性能的一项重大发展就是引入了交换机来取代基于以太网的网络中的集线器。5.WirelessLANshavebecomepopularinthehomeduetoeaseofinstallationanduse,andincommercialcomplexesofferingwirelessaccesstotheircustomers,oftenforfree.

因为易于安装和使用，无线局域网已在家庭中流行，也在向顾客提供无线接入（通常免