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第一章1、Datacommunication:isthetransferofdataformonedevicetoanotherviasomeformoftransmissionmedium.2、数据通讯五个方面：protocol、message、medium、sender、receiverprotocolisasetofsulesthatgoverndatacommunication。Itrepresentsanagreementbetweenthecommunicationdevices。themessageistheinformationtobecommunication。itconsistsoftext，number，picture，sound，orvideo-oranycombinationofthere。sendercanbeacomputer，workstation，telephonehandset，television，andsoon。thetransmissionmediumisthephysicalpathbywhichamessagetravelsfromsendertoreceiver。thereceiveisthedevicethatreceivesthemassage，itcanbeacomputer，3、networks网络：Anetworkisasetofdevices(oftenrefferredtoasnodes)connectedbymedialinks.4、networkcriteria网络指标：performance（性能）、reliable（可靠性）、security（安全性）5、reliable三个方面：frequentlyoffailure（故障时间间隔）、recoverytimeafterafailure（故障修复时间）、catastrophe（灾难性事故预防）6、protocol：aprotocolisasetofrulethatgoverndatacommunication，workstation，telephonehandset，television，andsoon。三要素：syntax（语法）semantics（语言）timing（时序）7、standardDefocto（byfactorbyconvention）实施标准standardDejure（bylaworbyregulation）法定标准8、STANDARDORGANIZATION标准组织standardcreationcommittees标准化委员会ISO:theinternationalstandardsorgnization国际化标准化组织ANSI：theAmericannationalstandardinstitute美国国家标准化协会IEEE:theinstituteofelectricalandelectronicengineers电气电子工程师协会EIA：theelectronicindustriesassociation电子工业联合会Bellcore：thebellcoreisanimportantsourceofdraftstandardstoANSI第二章1、lineconfiguration：piont-to-piont、multipoint、2、拓扑结构topology：mesh（网状）star（星形）bus（总线型）tree（树形）ring（环形）3、共享链路两种方式：（1）peer-to-peer（对等方式）：网状、环形（2）primary-secondary（主从方式）：树形、星形4、n个设备使用电缆条数：网状n(n-1)/2星形n5、传输方式transmissonmode:simplex（单工）、half-duplex（半双工）、full-duplex（全双工）simplex：onestationcantransmit，theothercanonlyreceive。Thecommunicationisundirectional单向传输half-duplex：eachstationcanbothtransmitandreceive，butnotatsametime双向传输，但不同时full-duplex：bothstationcantransmitandreceive。可同时双向传输6、网络的三种分类：LAN：cocalareanetwork。局域网MAN：metropolitanareanetwork。城域网WAN：wideaeranetwork万维网第三章1、对OSI模型解释：OSI（opensysteminterconnection）tofaciletatethedevelopmentofinteractivesystem。TheOSIisnotaprotocol，itisamodelforunderstandinganddesigninganetworkarchitecture。2、7层模式：physical物理层、datalink数据链路层、network网络层、transportation传输层、session会话层、persentation表示层、application应用层3、peer-to-peerprocess对等过程：theprocessesonsechmachinethatcommunicateatagivenlayerarecalledpeer-to-peerprocesses。4、物理层考虑的七个问题：（1）线路配置（2）数据传输模式（3）拓扑（4）信号（5）编码（6）接口（7）媒介5、七层各层的功能：（1）物理层：totransmitbits，toprovidemechanicalandelectricalspecifications。（2）数据链路层：toorganizebitsintoframs，toprovidenode-to-nodedelivery点到点。（3）网络层：tomovepacketsfromsourcetodestination，toprovideinternetworking。（4）传输层：toprovideend-to-endmessagedeliveryanderrorrecovery。（5）会话层：toestablish、manage、andterminatesession。（6）表示层：totranslate，encryptandcompressdata。（7）应用层：toallowaccesstonetworkresource。第四章1、频率单位：HZKHZGHZTHZ周期单位：smsusps2、频谱frequencyspectrum：thefrequencyspectrumofasignalisthecombinationofallsinewavesignalsthatsignal。带宽bandwidth：bandwidthofasignalisthewidthofthefrequencyspectrum。3、有效频谱：significantspectrum：istheportionofthesignalsspectrumthatcanadequatelyreproducetheoriginalsignal。有效带宽：thesignificantbandwidth：thebandwidthofthesignificantspectrum介质带宽：mediumbandwidth：thebandwidthofasignalwhichissentonatransmissionmedium。4、信道容量channelcapacity：isthemaximumbitrateatransmissionmediumcantransfer。决定因素：dependsonthetypeofencodingtechniqueandthesignal-to-noiseratioofsystem第五章1、编码的四种类型：digital/digital、analog/digital、digital/analog、analog/analog2、digital/digitalencoding的三种类型：unipolar单极性编码、bipolar双极性编码、polar极性编码3、bipolarencoding分类：AMI(bipolaralternatemarkinversion)信号交替反转码B8ZS（bipolar8-zerosubstitution）8零替换编码HDB3（high-densitybipolar3）高密度双极性3零编码4、PAM：pulseamplitudemodulation脉冲振幅调制PCM：pulsecodemodulation脉冲编码制（A-D）5、analog-PCM编码四步骤：（1）PAM：连续-离散采样保持（2）quantization量化：isamethodofassigningintegralvaluseinaspecificrange（3）binaryencoding二进制编码（4）digital/digitalencoding6、采样定理：thesamplingratemustbeatleast2timesthehighestfrequency7、digital/analogencoding四种方法：（1）ASK：amplitudeshiftkeying幅移键控（2）FSK：frequencyshiftkeying频移键控（3）PSK：phaseshiftkeying相移键控（4）QAM：quadratureamplitudemodulation正交调幅8、bitrate比特率：isthenumberofbitspersecond（bps）baudrate波特率：isthenumberofsignalunitspersecond（Bd）波特率小于等于比特率9、贷款公式psk：BW=NbaudASK:BW=（1+d)*Nbaud=NbaudFSK：BW=|fc1-fc0|+Nbaud带宽BW=波特率=比特率10、PSKconstellation：Adiagramcalledconstellationorphase-statediagramisusedtoshowtherelationshipbetweenphaseinPSK11、波特率和比特率的关系：ASK,FSK,2-PSK:baudrate=bitrate4-PSK，4-QAM:bitrate=2baudrate8-PSK，8-QAM：bitrate=3baudrate16-QAM：bitrate=4baudrate第六章1、digitaldatatransmission分类：parallel并行传输、serial串行传输（asynchronous异步，synchronous同步）2、异步传输解释：Inanasynchronoustransmissionmodewesendonestartbit（0）atthebeginningandoneormorestepbit（1）attheendofeachbyte。theremaybegapsbetweeneachbyte。3、串行同步：Insynchronoustransmissionwesendbitsoneafteranotherwithoutstart/stopbitsorgaps，itistheresponsibilityofthereceivetogroupthebitsintomeaningfulframe。4、DTE：dataterminalequipment（数据终端设备）ADTEisanydevicethatisasourceofordesitinationforbinarydigitaldata。DCE：datacircuit-terminationequipment（数