计算机专业英语（第3版）-练习及情境对话 课件 6 chapter6 Reading Material（阅读材料）

阅读材料ReadingMaterial计算机专业英语chaptersix

ComputerNetworkTechnologyMissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?1.VarietiesofEthernet计算机专业英语FastEthernet100BASE-T:Atermforanyofthethreestandardsfor100

Mbit/sEthernetovertwistedpaircables,Including100BASE-TX,100BASE-T4and100BASE-T2.Asof2009,100BASE-TXhastotallydominatedthemarket,andisoftenconsideredtobesynonymouswith100BASE-Tininformalusage.100BASE-TX:100

Mbit/sEthernetoverCategory5cables(usingtwooutoffourpairs).Similarstar-shapedconfigurationto10BASE-T.100BASE-T4:100

Mbit/sEthernetoverCategory3cables(asusedfor10BASE-Tinstallations).Usesallfourpairsinthecable,andislimitedtohalf-duplex.Nowobsolete,asCategory5cablesarethenorm.100BASE-T2:100

Mbit/sEthernetoverCategory3cables.Usingonlytwopairs,andsupportingfull-duplex,itisfunctionallyequivalentto100BASE-TX,butsupportsoldcable.Noproductssupportingthisstandardwasevermanufactured.100BASE-FX:100

Mbit/sEthernetoverfiber.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?1.VarietiesofEthernet计算机专业英语GigabitEthernet1000BASE-T:1

Gbit/soverunshieldedtwistedpaircoppercabling(atleastCategory5cables,withCategory5estronglyrecommended).1000BASE-SX:1

Gbit/sovershortrangemulti-modefiber.1000BASE-LX:1

Gbit/soverlongrangesingle-modefiber.1000BASE-CX:Ashort-haulsolution(upto25

m)forrunning1

Gbit/sEthernetoverspecialcoppercable.Predates1000BASE-T,andnowobsolete.

10-gigabitEthernetThe10gigabitEthernetfamilyofstandardsencompassesmediatypesforsingle-modefibre(longhaul),multi-modefibre(upto300

m),copperbackplane(upto1

m)andcoppertwistedpair(upto100

m).ItwasfirststandardisedasIEEEStd802.3ae-2002,butisnowincludedinIEEEStd802.3-2008.MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?1.VarietiesofEthernet计算机专业英语10GBASE-SR:designedtosupportshortdistancesoverdeployedmulti-modefibercabling,ithasarangeofbetween26

mand82

mdependingoncabletype.Italsosupports300

moperationoveranew2000

MHz·kmmulti-modefiber.10GBASE-LX4:useswavelengthdivisionmultiplexingtosupportrangesofbetween240

mand300

moverdeployedmulti-modecabling.Alsosupports10

kmoversingle-modefiber.10GBASE-LRand10GBASE-ER:thesestandardssupport10

kmand40

kmrespectivelyoversingle-modefiber.10GBASE-SW,10GBASE-LWand10GBASE-EW.ThesevarietiesusetheWANPHY,designedtointeroperatewithOC-192/STM-64SONET/SDHequipment.Theycorrespondatthephysicallayerto10GBASE-SR,10GBASE-LRand10GBASE-ERrespectively,MissLi:AsalesgirlinComputerTownMr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?1.VarietiesofEthernet计算机专业英语andhenceusethesametypesoffiberandsupportthesamedistances.(ThereisnoWANPHYstandardcorrespondingto10GBASE-LX4.)10GBASE-T:designedtosupportcoppertwistedpairandwasspecifiedbytheIEEEStd802.3an-2006whichhasbeenincorporatedintotheIEEEStd802.3-2008.MissLi:AsalesgirlinComputerTownPreviously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.Mr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?2.ARPANET计算机专业英语TheARPANET(AdvancedResearchProjectsAgencyNetwork),createdbytheARPAoftheUnitedStatesDepartmentofDefenseduringtheColdWar,wastheworld’sfirstoperationalpacketswitchingnetwork,andthepredecessoroftheglobalInternet.Packetswitching,nowthedominantbasisforbothdataandvoicecommunicationworldwide,wasanewandimportantconceptindatacommunication.Previously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.MissLi:AsalesgirlinComputerTownPreviously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.Mr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?2.ARPANET计算机专业英语Withpacketswitching,asystemcoulduseonecommunicationlinktocommunicatewithmorethanonemachinebydisassemblingdataintodatagrams,thengathertheseaspackets.Notonlycouldthelinkbeshared(muchasasinglepostboxcanbeusedtopostletterstodifferentdestinations),buteachpacketcouldberoutedindependentlyofotherpackets.AformofpacketswitchingdesignedbyLincolnLaboratoryscientistLawrenceRobertsunderlaythedesignofARPANET.BackgroundofARPANETTheearliestideasofacomputernetworkintendedtoallowgeneralcommunicationbetweenusersofvariouscomputerswereformulatedbyJ.C.R.LickliderofBolt,BeranekandNewman(BBN)inAugust1962,inaseriesofmemosdiscussinghis“IntergalacticComputerNetwork”concept.TheseideascontainedalmosteverythingthattheInternetistoday.MissLi:AsalesgirlinComputerTownPreviously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.Mr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?2.ARPANET计算机专业英语InOctober1963,LickliderwasappointedheadoftheBehavioralSciencesandCommandandControlprogramsatARPA(asitwasthencalled),theUnitedStatesDepartmentofDefenseAdvancedResearchProjectsAgency.HethenconvincedIvanSutherlandandBobTaylorthatthiswasaveryimportantconcept,althoughheleftARPANETbeforeanyactualworkonhisvisionwasperformed.ARPAandTaylorcontinuedtobeinterestedincreatingacomputercommunicationnetwork,inparttoallowARPA-sponsoredresearchersinvariouslocationstousevariouscomputerswhichARPAwasproviding,andinparttomakenewsoftwareandotherresultswidelyavailablequickly.Taylorhadthreedifferentterminalsinhisoffice,connectedtothreedifferentcomputerswhichARPAwasfunding:onefortheSDCQ-32inSantaMonica,oneforProjectGenieattheUniversityofCalifornia,Berkeley,andoneforMulticsatMIT.Taylorlaterrecalled:MissLi:AsalesgirlinComputerTownPreviously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.Mr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?2.ARPANET计算机专业英语“Foreachofthesethreeterminals,Ihadthreedifferentsetsofusercommands.SoifIwastalkingonlinewithsomeoneatS.D.C.andIwantedtotalktosomeoneIknewatBerkeleyorM.I.T.aboutthis,IhadtogetupfromtheS.D.C.terminal,gooverandlogintotheotherterminalandgetintouchwiththem.Isaid,oh,man,it’sobviouswhattodo:Ifyouhavethesethreeterminals,thereoughttobeoneterminalthatgoesanywhereyouwanttogo.ThatideaistheARPANET.”Somewhatcontemporaneously,anumberofpeoplehad(mostlyindependently)workedoutvariousaspectsofwhatlaterbecameknownas“packetswitching”,withthefirstpublicdemonstrationbeingmadebytheUK’sNationalPhysicalLaboratory(NPL)on5August5,1968.ThepeoplewhocreatedtheARPANETwouldeventuallydrawonallthesedifferentsources.MissLi:AsalesgirlinComputerTownPreviously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.Mr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?3.Hotmail计算机专业英语InDecember1995,SabeerBhatiaandJackSmithvisitedtheInternetventurecapitalistDraperFisherJurvetsonandproposeddevelopingafreeWeb-basedE-mailsystem.TheideawastogiveafreeE-mailaccounttoanyonewhowantedone,andtomaketheaccountsaccessiblefromtheWeb.WithWeb-basedE-mail,anyonewithaccesstotheWeb——say,fromaschoolorcommunitylibrary——couldreadandsendE-mails.Furthermore,web-basedE-mailwouldoffergreatmobilitytoitssubscribers.Inexchangefor15percentofthecompany,DraperFisherJurvetsonfinancedBhatiaandSmith,whoformedacompanycalledHotmail.Withthreefull-timepeopleand12～14part-timepeoplewhoworkedforstockoptions,theywereabletodevelopandlaunchtheserviceinJuly1996.Withinamonthafterlaunchtheyhad100

000subscribers.Thenumberofsubscriberscontinuedtogrowrapidly,withalloftheirsubscribersbeingexposedtoadvertisingbannerswhilereadingtheirE-mail.MissLi:AsalesgirlinComputerTownPreviously,datacommunicationwasbasedontheideaofcircuitswitching,asintheoldtypicaltelephonecircuit,whereadedicatedcircuitistiedupforthedurationofthecallandcommunicationisonlypossiblewiththesinglepartyontheotherendofthecircuit.Mr.Zhang:AcomputerconsumerwhoknowslittleaboutcomputerLi:CanIhelpyou,Sir?Zhang:Yes.I’dliketobuyacomputer,butIknowlittleaboutit.Li:Doyoulikeabrandmachineoracompatiblemachine?3.Hotmail计算机专业英语withalloftheirsubscribersbeingexposedtoadvertisingbannerswhilereadingtheirE-mail.InDecember1997,lessthan18monthsafterlaunchingtheservice,Hotmailhadover12millionsubscribersandwasacquiredbyMicrosoft,reportedlyfor$400milliondollars.

ThesuccessofHotmailisoftenattributedtoits“first-moveradvantage”andtotheinherent“viralmarketing”ofE-mail.Hotmailhadafirst-moveradvantagebecauseitwasthefirstcompanytoofferWeb-basedE-mail.Othercomp