Lessons2NetworkClassificationModule3ConsolidationExercise（鞏固練習(xí)）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（練習(xí)鞏固）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個(gè)域網(wǎng) CSMA/CD:CarrierSenseMultipleAccesswithCollisionDetection帶沖突檢測的載波監(jiān)聽多路訪問 MAN:MetropolitanAreaNetwork城域網(wǎng)WPA:Wi-FiProtectedAccessWi-Fi保護(hù)接入U(xiǎn)TP:UnshieldedTwistedPaired無屏蔽雙絞線LAN:LocalAreaNetwork局域網(wǎng)WLAN:WirelessLocalAreaNetwork無線局域網(wǎng)RFID:RadioFrequencyIdentification無線射頻識別WEP:WiredEquivalentPrivacy有線等效加密WAN:WideAreaNetwork廣域網(wǎng)III.TranslatethefollowingsentencesintoChinese.1.Tohelptheseusers,somecompaniesgottogethertodesignashort-rangewirelessnetworkcalledBluetoothtoconnectthesecomponentswithoutwires.為幫助這些用戶，有些公司共同設(shè)計(jì)了一個(gè)名為“藍(lán)牙”的短程無線網(wǎng)絡(luò)來無線連接這些部件。2.Knowingthisboundmakesitpossibletousecertainkindsofdesignsthatwouldnototherwisebepossible.知道該范圍（指最長傳輸時(shí)間）就可以使用某些原本不可能使用的特殊設(shè)計(jì)。3．Ethernetwasdesignedtoaccommodatemultiplecomputersthatwereinterconnectedonasharedbustopology.設(shè)計(jì)以太網(wǎng)就是為了接入通過共享總線拓?fù)浠ミB的多臺計(jì)算機(jī)。4．AsignificantdevelopmentthatenhancedLANperformancewastheintroductionofswitchestoreplacehubsinEthernet-basednetworks.提高局域網(wǎng)性能的一項(xiàng)重大發(fā)展就是引入了交換機(jī)來取代基于以太網(wǎng)的網(wǎng)絡(luò)中的集線器。5.WirelessLANshavebecomepopularinthehomeduetoeaseofinstallationanduse,andincommercialcomplexesofferingwirelessaccesstotheircustomers,oftenforfree.

因?yàn)橐子诎惭b和使用，無線局域網(wǎng)已在家庭中流行，也在向顧客提供無線接入（通常免