計算機專業(yè)英語（第3版）-練習(xí)及情境對話 課件 3.8　Reading and Comparing（對照閱讀）

對照閱讀ReadingandComparing

計算機專業(yè)英語chapterthree

FoundationofComputerNetworkMissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?AreWirelessNetworksSecure?計算機專業(yè)英語無線網(wǎng)絡(luò)安全嗎？Nocomputernetworkistrulysecure,buthowdoeswirelessnetworksecuritystackupwiththatoftraditionalwirednetworks?Unfortunately,nocomputernetworkistrulysecure.It’salwaystheoreticallypossibleforeavesdropperstoviewor“snoop”thetrafficonanynetwork,andit’softenpossibletoaddor“inject”unwelcometrafficaswell.However,somenetworksarebuiltandmanagedmuchmoresecurelythanothers.Forbothwiredandwirelessnetworksalike,therealquestiontoanswerbecomes—isitsecureenough?沒有哪個計算機網(wǎng)絡(luò)是真正安全的，那么無線網(wǎng)絡(luò)與傳統(tǒng)有線網(wǎng)絡(luò)相比又如何呢？遺憾的是，沒有一個計算機網(wǎng)絡(luò)是真正安全的。從理論上講，任何網(wǎng)絡(luò)上的信息總是可能被偷看或探聽的，并且網(wǎng)絡(luò)中經(jīng)?？赡軙惶砑踊蜃⑷胍恍┎皇軞g迎的信息。然而，一些更安全的網(wǎng)絡(luò)已經(jīng)建立并運行起來了。有線網(wǎng)絡(luò)和無線網(wǎng)絡(luò)都一樣，它們真正要回答的問題是——它是足夠安全的嗎？MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?AreWirelessNetworksSecure?計算機專業(yè)英語無線網(wǎng)絡(luò)安全嗎？Wirelessnetworksaddanextralevelofsecuritycomplexitycomparedtowirednetworks.Whereaswirednetworkssendelectricalsignalsorpulsesoflightthroughcable,wirelessradiosignalspropagatethroughtheairandarenaturallyeasiertointercept.SignalsfrommostwirelessLANs(WLANs)passthroughexteriorwallsandintonearbystreetsorparkinglots.與有線網(wǎng)絡(luò)相比，無線網(wǎng)絡(luò)增加了一個額外的復(fù)雜的安全級別。主要是鑒于有線網(wǎng)絡(luò)是通過電纜來傳送電信號或光波的，而無線電信號卻是在空氣中傳播，自然容易被截取。大多數(shù)無線網(wǎng)絡(luò)發(fā)出的信號都是通過外墻進(jìn)入附近的街道或停車場的。MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?AreWirelessNetworksSecure?計算機專業(yè)英語無線網(wǎng)絡(luò)安全嗎？Networkengineersandothertechnologyexpertshavecloselyscrutinizedwirelessnetworksecuritybecauseoftheopen-airnatureofwirelesscommunications.Thepracticeofwardriving,forexample,exposedthevulnerabilitiesofhomeWLANsandacceleratedthepaceofsecuritytechnologyadvancesinhomewirelessequipment.由于無線通信的開放環(huán)境，網(wǎng)絡(luò)工程師和其他技術(shù)專家已經(jīng)對無線網(wǎng)絡(luò)的安全性進(jìn)行了細(xì)致的考察。對無線電感應(yīng)（比如，家用無線局域網(wǎng)所暴露出的弱點）防護(hù)措施的推進(jìn)，加速了家用無線局域網(wǎng)設(shè)備安全技術(shù)的步伐。MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?AreWirelessNetworksSecure?計算機專業(yè)英語無線網(wǎng)絡(luò)安全嗎？Overall,conventionalwisdomholdsthatwirelessnetworksarenow“secureenough”touseinthevastmajorityofhomes,andmanybusinesses.Securityfeatureslike128-bitWEPandWPAcanscrambleor“encrypt”networktrafficsothatitscontentscannoteasilybedecipheredbysnoopers.Likewise,wirelessroutersandaccesspoints(APs)incorporateaccesscontrolfeaturessuchasMACaddressfilteringthatdenynetworkrequestsfromunwantedclients.總的來看，大家普遍認(rèn)為，對于廣大家庭和眾多的商家而言，無線網(wǎng)絡(luò)現(xiàn)在已經(jīng)是足夠安全的了。像128位的WEP協(xié)議和WPA協(xié)議加密網(wǎng)絡(luò)信息的安全特性就使得窺探者不容易解密。同樣的，無線網(wǎng)絡(luò)路由器和訪問點混合存取控制的特性（如物理地址過濾）也能拒絕非法用戶的網(wǎng)絡(luò)請求。MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?AreWirelessNetworksSecure?計算機專業(yè)英語無線網(wǎng)絡(luò)安全嗎？Obviously,everyhomeorbusinessmustdetermineforthemselvesthelevelofrisktheyarecomfortableintakingwhenimplementingawirelessnetwork.Thebetterawirelessnetworkisadministered,themoresecureitbecomes.However,theonlytrulysecurenetworkistheoneneverbuilt!顯然，當(dāng)使用無線網(wǎng)絡(luò)時，每個家庭用戶和商家都必須確定他們自己的安全級別，以獲得最合適的網(wǎng)絡(luò)信息。當(dāng)然一個更有效的無線網(wǎng)絡(luò)管理，也會使它變得更安全些。然而，一個絕對安全的網(wǎng)絡(luò)還從未建立起來。MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?Notes計算機專業(yè)英語Notes1．WEP：ShortforWiredEquivalentPrivacy,asecurityprotocolforwirelesslocalareanetworks(WLANs)definedinthe802.11bstandard.WEPisdesignedtoprovidethesamelevelofsecurityasthatofawiredLAN.（WEP：等有線秘密的縮寫，在802.11