计算机文化5

ComputerConcepts2013Chapter5LocalAreaNetworks5ChapterContentsSectionA:NetworkBuildingBlocks（网络积木）SectionB:WiredandWirelessTechnologies（有线和无线技术）SectionC:NetworkSetup（网络设置）SectionD:SharingFiles（共享文件）SectionE:WirelessSecurity（无线网络安全）Chapter5:LocalAreaNetworks25FastPollTrue/FalseQuestionsAnswerAforTrueandBforFalse050100ThenetworkstypicallyinstalledbyindividualsinhomesareclassifiedasLANs.050200Highbandwidthnetworks,suchascableTVandDSLarereferredtoasbroadband.050300Whenyousendane-mailmessageoveranetwork,itischoppedupintopackets.050400TheIPaddressassignedtoyourcomputerontheInternetisderivedfromyourcomputer’sMACaddress.050500Wirednetworkconnectionscanofferhigherspeedsthanwirelessconnections.Chapter5:LocalAreaNetworks35FastPollTrue/FalseQuestionsAnswerAforTrueandBforFalse050600ThemostpopulartypeofwiredconnectionisEthernet.050700Networkspeedsaremeasuredinmegabytesandgigabytes.050800Manywirelessconnectionsuseradiowavestotransmitdata.050900BluetoothisawirelesstechnologyusedforWANs.Chapter5:LocalAreaNetworks45FastPollTrue/FalseQuestionsAnswerAforTrueandBforFalse051000Awirelessinfrastructurenetworkusesacentralizedbroadcastingdevice,suchasawirelessaccesspointorrouter.051100Wirelessconnectionsarelesssecurethanwirednetworks.051200Ahubcanbeusedtoextendanetworkbyaddingadditionalwireddevices.051300Toconfigurearouter,youusuallyhavetostartabrowserandentertherouter’sIPaddress.Chapter5:LocalAreaNetworks55FastPollTrue/FalseQuestionsAnswerAforTrueandBforFalse051400Ahomegroupisatemporarynetworkofhandheldcomputers.051500Publickeyencryptionusesapublickeytoencryptmessages,butaprivatekeyisrequiredtodecryptmessages.Chapter5:LocalAreaNetworks65SectionA:NetworkBuildingBlocksNetworkClassifications/网络分类LANAdvantagesandDisadvantages/局域网优点和缺点NetworkDevices/网络设备NetworkLinks/网络连接CommunicationsProtocols/通信协议Chapter5:LocalAreaNetworks75Question052100Networkscomeinmanysizesandusemanydifferenttechnologies,yettheyallneedtocommunicatewitheachother.Whatisthekeytonetworkintercommunication?A.CircuitswitchingB.NetworkprotocolsC.NetworktopologyD.Peer-to-peertechnologyChapter5:LocalAreaNetworks85NetworkClassificationsPersonalAreaNetwork(PAN-个域网)–interconnectionofpersonaldigitaldevicesorconsumerelectronicsLocalAreaNetwork(LAN局域网)–usuallyconnectscomputersinasinglebuildingWirelessLocalAreaNetwork：（WLAN无线局域网）-利用电磁波在空气中发送和接，而无需线缆介质。WLAN的数据传输速率已经能够达到最高1000Mbps，传输距离可远至20km以上。无线联网方式是对有线联网方式的一种补充和扩展，使网上的计算机具有可移动性，网络联通问题。Metropolitan(城市)AreaNetwork(MAN城域网)–publichigh-speednetworkwithrangeofabout50milesWideAreaNetwork(WAN广域网)–coversalargegeographicalareaandtypicallyconsistsofseveralsmallernetworksChapter5:LocalAreaNetworks95LANAdvantagesandDisadvantagesLANsenablepeopletoworktogetherSharingnetworkedsoftwarecanreducecostsSharingdataonaLANcanincreaseproductivity（生产力）SharingnetworkedhardwarecanreducecostsSharingnetworkedhardwarecanprovideaccesstoawiderangeofservicesandspecializedperipheraldevices（共享网络硬件可以提供范围广泛的服务和专业的外围设备）Chapter5:LocalAreaNetworks105LANAdvantagesandDisadvantages（局域网的优缺点）OnedisadvantageofLANsisthatwhenanetworkmalfunctions,alltheresourcesyou’reaccustomedtoaccessingareunavailableuntilthenetworkisrepaired（局域网的缺点之一是，当网络出现故障，你习惯于访问资源在网络修复之前不可用）LANsarevulnerabletounauthorizedaccess（局域网容易受到未经授权的访问）LANsaremorevulnerabletomaliciouscode（局域网更容易受到恶意代码的攻击）Chapter5:LocalAreaNetworks115NetworkDevices（网络设备）Eachconnectionpointonanetworkisanode（节点）ToconnecttoaLAN,acomputerrequiresnetworkcircuitry,sometimesreferredtoasanetworkinterfacecard(NIC网络接口卡)Anetworkedperipheral,ornetwork-enabledperipheral,isanydevicethatcontainsnetworkcircuitrytodirectlyconnecttoanetwork（网络外围设备或网络使能的外围设备，是直接连接到网络的包含网络电路的任何设备）Anetworkdevice,ornetworkappliance,isanyelectronicdevicethatbroadcastsnetworkdata,boostssignals,orroutesdatatoitsdestination（网络设备，或是任何网络装置，是那些传输网络数据，增强信号，或路由数据到其目的地的任何电子设备）Chapter5:LocalAreaNetwor125NetworkDevicesChapter5:LocalAreaNetworksDSL(DigitalSubscriberLine数字用户专线)13DSL包括ADSL(AsymmetricDigitalSubscriberLine,非对称数字用户线)、RADSL()、HDSL和VDSL等等。5NetworkLinks（网络连接）Acommunicationschannel,orlink,isaphysicalpathorfrequencyforsignaltransmissions（通信信道或链接是信号传输一个物理路径或频率Bandwidthisthetransmissioncapacityofacommunicationschannel（带宽是通信信道的传输容量））Broadband（宽带:）Narrowband（窄带:）Chapter5:LocalAreaNetworks145CommunicationsProtocolsRulesforefficientlytransmittingdatafromonenetworknodetoanother（为有效地传输数据从一个网络节点到另一个节点的规则集):Dividemessagesintopackets（将信息转换成数据包）Affixaddressestopackets（给数据包加上地址）Initiatetransmission(启动传输)Regulateflowofdata(规范数据流)Checkfortransmissionerrors(检查传输误差)Acknowledgereceiptoftransmitteddata（承认发送数据的接收）Chapter5:LocalAreaNetworks155CommunicationsProtocolsApacketisa“parcel”ofdatathatissentacrossacomputernetwork（数据包是一个通过计算机网络进行发送的数据“包裹”）Circuit-switchingtechnologyvs.packetswitchingtechnology（电路交换技术和分组交换技术）电路交换分组交互:LocalAreaNetworks165CommunicationsProtocolsEverypacketthattravelsov