計算機導論課件：Chapter06 The Internet

Chapter6

TheInternetChapterContentsSectionA:InternetTechnologySectionB:FixedInternetAccessSectionC:PortableandMobileInternet AccessSectionD:InternetServicesSectionE:InternetSecurityChapter6:TheInternet2SectionA:InternetTechnologyChapter6:TheInternet3BackgroundTheARPANET,createdin1969,connectedcomputersatUCLA,StanfordResearchInstitute,UniversityofUtah,andUniversityofCaliforniaatSantaBarbaraEarlyInternetpioneersusedprimitivecommand-lineuserinterfacestosende-mail,transferfiles,andrunscientificcalculationsonInternetsupercomputersWithanestimated500millionnodesandmorethan2billionusers,theInternetishugeChapter6:TheInternet4InternetInfrastructureTheInternetisnotownedoroperatedbyanysinglecorporationorgovernmentTheInternetbackboneisanetworkofhigh-capacityroutersandfiber-opticcommunicationslinksthatprovidesthemainroutesfordatatrafficacrosstheInternetBackbonelinksandroutersaremaintainedbynetworkserviceproviders(NSPs)NSPequipmentandlinksaretiedtogetherbynetworkaccesspoints(NAPs)AnInternetserviceprovider(ISP)isacompanythatoffersInternetaccesstoindividuals,businesses,andsmallerISPsChapter6:TheInternet5InternetInfrastructureChapter6:TheInternet6InternetInfrastructureTocommunicatewithanISP,yourcomputerusessometypeofcommunicationsdevice,suchasamodemChapter6:TheInternet7InternetInfrastructureInternetProtocols,

Addresses,andDomainsAcomputercanhaveapermanentlyassignedstaticIPaddressoratemporarilyassigneddynamicIPaddressChapter6:TheInternet9InternetProtocols,

Addresses,andDomainsChapter6:TheInternet10AdomainnameisakeycomponentofWebpageaddressesande-mailaddressesInternetProtocols,

Addresses,andDomainsChapter6:TheInternet11InternetProtocols,

Addresses,andDomainsChapter6:TheInternet12InternetProtocols,

Addresses,andDomainsConnectionSpeedDatatravelsovertheInternetatanincrediblespeedTheelapsedtimefordatatomakearoundtripfrompointAtopointBandbacktopointAisreferredtoaslatencyPingTracerouteUpstreamvs.downstreamspeedChapter6:TheInternet14ConnectionSpeedChapter6:TheInternet15ConnectionSpeedWhenupstreamspeedsdifferfromdownstreamspeeds,youhaveanasymmetricInternetconnectionWhenupstreamanddownstreamspeedsarethesame,youhaveasymmetricInternetconnectionInternetconnectionoptionsFixedInternetaccessPortableInternetaccessMobileInternetaccessChapter6:TheInternet16ConnectionSpeedChapter6:TheInternet17QuestionOnereasontheInternetworksisbecauseTCP/IPoffersaglobaladdressingstandard.WhichoneofthefollowingisaccurateinthecontextofInternetaddresses?A.IPv6addressessuchasarededicated

toeducationalinstitutions.B.TopleveldomainslikeEarthLinkorAOLareadequate

formostconsumers.C.Adomainname,suchascorrespondsto

auniqueIPaddress.D.AdynamicIPaddressbeginswithwww.Chapter6:TheInternet18AnswerCChapter6:TheInternet19SectionB:FixedInternetAccessChapter6:TheInternet20Dial-upConnectionsAdial-upconnectionisafixedInternetconnectionthatusesavoicebandmodemandtelephonelinestotransportdatabetweenyourcomputerandyourISPChapter6:TheInternet21Dial-upConnectionsAvoicebandmodemconvertsthesignalsfromyourcomputerintoaudibleanalogsignalsthatcantravelovertelephonelinesModemspeedismeasuredinbitspersecondChapter6:TheInternet22Dial-upConnectionsDSLDSLisahigh-speed,digital,always-onInternetaccesstechnologythatrunsoverstandardphonelinesThespeedofaDSLconnectionvariesDSLmodemDSLfilterChapter6:TheInternet24DSLChapter6:TheInternet25CableInternetServiceCableInternetserviceisameansofdistributingalways-onbroadbandInternetaccessoverthesameinfrastructurethatofferscabletelevisionserviceChapter6:TheInternet26DSL,ISDN,and

DedicatedLinesCableInternetServiceCablemodemsconvertyourcomputer’ssignalintoonethatcantravelovertheCATVnetworkAlways-onconnectionDOCSIS-compliantcable

modemsChapter6:TheInternet28SatelliteInternetServiceSatelliteInternetservicedistributesalways-on,high-speedasymmetricInternetaccessbybroadcastingsignalstoandfromapersonalsatellitedishAsatellitemodemisadevicethatmodulatesdatasignalsfromacomputerintoafrequencybandthatcanbecarriedtothesatellitedishwhereitisconvertedtoanotherfrequency,amplified,andtransmittedChapter6:TheInternet29FixedWirelessServiceFixedwirelessInternetservicebroadcastssignalsinordertoofferInternetaccesstolargeareasWiMAXAWiMAXsystemtransmitsdata

toandfromWiMAXantennas

mountedontowersUnderidealconditions,WiMAX

cantransmitdataat70MbpsChapter6:TheInternet30FixedInternetConnectionRoundupChapter6:TheInternet31QuestionAlthoughISPsofferInternetaccessthroughdial-up,satellites,WiMAX,andDSL,cableInternetiscurrentlythepreferredaccessmethod.Why?A.Itistheleastexpensive.B.Itisthefastestandmostwidelyavailable

technology.C.Ithasthehighestlatency.D.ItwastheoriginalInternetaccesstechnology.Chapter6:TheInternet32AnswerBChapter6:TheInternet33SectionC:PortableandMobileInternetAccessChapter6:TheInternet34InternetToGoPortableInternetaccesscanbedefinedastheabilitytoeasilymoveyourInternetservicefromonelocationtoanotherMobileInternetaccessoffersacontinuousInternetconnectionasyouarewalkingorridinginabus,car,train,orplaneChapter6:TheInternet35Wi-FiHotspotsAWi-FihotspotisanareainwhichthepubliccanaccessaWi-FinetworkthatoffersInternetserviceWi-FidoesnottypicallyprovideacceptablemobileInternetaccessbecauseyoucanonlyremainconnectedwithinrangeofthenetwork’shotspotChapter6:TheInternet36PortableandMobileWiMAXWiMAXcanbeusedasaportabletechnologybecauseInternetaccessisavailabletosubscribersanywherewithinatower’scoverageareaYouusethesameInternetserviceproviderwhetheryouareathomeorontheroadMobileWiMAXChapter6:TheInternet37PortableSatelliteServiceChapter6:TheInternet38CellularDataServicesUsingcellphonetechnologytoaccesstheInternetoffersmobilitythatisnotyetpossiblewithmostoftoday’swiredorwirelesscomputernetworktechnologiesChapter6:TheInternet39CellularDataServices4Gtechnologyprovidespeakdataratesof100Mbpswhileadeviceisinmotion,or1GbpsrateswhenadeviceisstationaryWAP(WirelessApplicationProtocol)isacommunicationsprotocolthatprovidesInternetaccessfromhandhelddevicesFortherealInternet,cellularserviceprovidersofferdataservices,sometimesreferredtoasmobilebroadbandMostcellularserviceprovidersofferwirelessmodemsforbroadbanddataaccessChapter6:TheInternet40CellularDataServicesMiFiisabrandnameforacompact,mobile,wirelessrouterofferedbyNovatelWirelessSomecellphones,suchastheDroidsandiPhones,canactasaWi-FihotspotbybecomingtherouterforawirelessnetworkTetheringChapter6:TheInternet41QuestionWhatisthedifferencebetweenportableInternetaccessandmobileInternetaccess?A.Withportableaccessyoucannotworkonlinewhile

movingveryfar.B.Mobileaccessislessexpensivethanportableaccess.C.Portableaccessrequirescables,whereasmobile

accessdoesnot.D.Portableaccessrequiresacellphone,whereas

mobileaccessrequiresanotebookcomputer.Chapter6:TheInternet42AnswerAChapter6:TheInternet43SectionD:InternetServicesChapter6:TheInternet44CloudComputingCloudcomputingdependsonagridofservers,storagedevices,andprotocolsthatofferInternet-accessiblecomputingservicesrangingfromconsumer-levelmediasharingtoofficeproductivityapplicationsandcomplexcorporatedataprocessingSoftwareasaService(SaaS)Chapter6:TheInternet45CloudComputingChapter6:TheInternet46Real-TimeMessagingAnetworked-based,real-timemessagingsystemallowspeopletoexchangeshortmessageswhiletheyareonlineInstantmessaging(IM)ChatChapter6:TheInternet47VoiceoverIPVoIP(VoiceoverInternetProtocol)orVoiceoverIP,isatechnologyinwhichabroadbandInternetconnectionisusedtoplacetelephonecallsinsteadoftheregularphonesystemIfyouwanttosetupfreecomputer-to-computerVoIP,youandthepeopleyoucommunicatewithcandownloadandinstallfreewareoropensourceVoIPclientsChapter6:TheInternet48Forums,Wikis,Blogs,

andTweetsAnInternetforumisaWeb-basedonlinediscussionsitewhereparticipantspostcommentstodiscussionthreadsAwikiallowsparticipantstomodifypostedmaterialAblog(shortforWeblog)issimilartoanonlinediary;itismaintainedbyonepersonandcontainsaseriesofentriesononeormoretopicsAtweetisashortmessageof140charactersorless,postedtotheTwitterWebsiteChapter6:TheInternet49Forums,Wikis,Blogs,

andTweetsChapter6:TheInternet50GridComputingAgridcomputingsystemisanetworkofcomputersharnessedtogethertoperformprocessingtasksSETI@homeprojectChapter6:TheInternet51FTPChapter6:TheInternet52FTPChapter6:TheInternet53FileSharingNetworksFilesharing,sometimescalledP2Pfilesharing,allowsuserstoobtainfilesfromotheruserslocatedanywhereontheInternetBitTorrentisafilesharingprotocolthatdistributestheroleoffileserveracrossacollectionofdispersedcomputersChapter6:TheInternet54QuestionOntheInternet,applicationprotocolsprovideconsumerswithmanyusefulservices.WhichoneofthefollowingcorrectlydescribesanInternet-basedapplicationprotocol?A.ChatandInstantmessaginguseInternetVoIP

protocol.B.FilescanbesharedovertheInternetusingFTPor

BitTorrentprotocols.C.CloudprotocolssuchasSETIcontroldistributed

processinggrids.D.P2Pisusedtoencryptpersonalinformationtokeepit

private.Chapter6:TheInternet55AnswerBChapter6:TheInternet56SectionE:InternetSecurityIntrusionAttemptsSecuringPortsNATVirtualPrivateNetworksChapter6:TheInternet57IntrusionAttemptsAnintrusionisanyaccesstodataorprogramsbyhackers,criminals,orotherunauthorizedpersonsAcommunicationsportisthedoorwaythatallowsacomputertoexchangedatawithotherdevicesAportprobe(orportscan)usesautomatedsoftwaretolocatecomputersthathaveopenportsandarevulnerabletounauthorizedaccessChapter6:TheInternet58IntrusionAttemptsChapter6:TheInternet59SecuringPortsChapter6:TheInternet60SecuringPortsAfirewallissoftwareorhardwaredesignedtofilteroutsuspiciouspacketsattemptingtoenterorleaveacomputerSharingprintersorfilesonaLANortheInternetrequiresopenportssothedatacanbetransferredtoandfromyourcomputerChapter6:TheInternet61NATRoutersareintendedtoworkwithinLANstomonitoranddirectpacketsbeingtransportedfromonedevicetoanotherAroutableIPaddressisonethatcanbeaccessedbypacketsontheInternetAprivateIPaddressisanon-routableIPaddressthatcanbeusedwithinaLAN,butnotforInternetdatatransportChapter6:TheInternet62NATChapter6:TheInternet63NATNetworkaddresstranslation(NAT)istheprocessyourrouterusestokeeptrackofpacketsandtheircorrespondingprivateorpublicIPaddressesChapter6:TheInternet64VirtualPrivateNetworksItispossibletosecureremoteconnectionsbysettingupvirtualprivatenetwork(VPN)accesstoaremoteaccessserverinthecorporateofficeAccesstoaVPNisusuallybyinvitationonly;employeeswhoneedtoaccessaVPNaregiventhenecessaryinstructions,addresses,andpasswordstomakeconnectionsChapter6:TheInternet65VirtualPrivateNetworksChapter6:TheInternet66QuestionSecuringyourcomputerfromInternet-basedintrusionsisanimportantaspectofcomputersecurity.WhichoneofthefollowingisNOTausefulsecuritytechnique?A.SettingupNATonarouterB.ActivatingfirewallsoftwareC.CheckingthestatusofsoftwareportsD.Activatingyourcomputer’sfilesharingoptionsChapter6:TheInternet67AnswerDChapter6:TheInternet68FastPollTrue/FalseQuestions

AnswerAforTrueandBforFalse（1）NAPssuchasEarthlinkandComcastofferdial-upandcableInternetaccess.（2）TCP,IP,UDP,HTTP,andFTPareexamplesofprotocolsusedontheInternet.（3）00isanexampleofanIPaddress.（4）.eduand.caareexamplesoftop-leveldomains.Chapter6:TheInternet69FastPollTrue/FalseQuestions

AnswerAforTrueandBforFalse（5）TheDomainNameSystemstoresIPaddressesandtheirequivalentdomainnames.（6）UtilitiessuchasPingandTraceroutehelpyougaugethespeedofyourInternetconnection.（7）10MbpsisanarrowbandInternetconnection.（8）Dial-upandDSLprovideInternetaccessusingtelephonecabling.