计算机网路原理讲义Chapter1pdf下载(3)

下节课介绍影响网路功耗的一个重要诱因：分组交换网中的数据分组的推迟和遗失。主要教学环节：地理介质绞合线同轴电缆线光纤无线电波ISP和主干网教学过程：地理介质时间分配：分钟教学方式：讲授教学内容：本次课教与上海交通学院计算机大学计算机网路原理mdashmdash第一章‰Bit:propagatesbetweensphysicallink:whatliesbetweentransmitterreceiveredia:nsolidmedia:copper,fiber,coax‰gnalspropagatefreely,eg,radio双教学wistedPair(TP)transmitterrcvrpair‰‰guidedm‰signalspropagatei‰unguidedmedia:si绞线时间分配：分钟方式：讲授教学内容：Tcopperwiresditionalphonewires,MbpsEthernetnet‰twoinsulated‰Category:tra‰Category:MbpsEther上海交通学院计算机大学计算机网路原理mdashmdash第一章PAIR重点：绞合线的特性及适用范围同轴电缆线分钟教学方式：教学内容：PhysicalMedia:coax,时间分配：讲授Coaxialcable:‰uctors‰‰‰‰‰multiplechanneloncable‰HFC重点：同轴电缆线的特性及适用范围twoconcentriccoppercondbidirectionalbaseband:‰singlechanneloncablelegacyEthernetbroadband:PAIRPAIRPAIRPAIRTRTRTRTREIATAPAIRPAIRPAIRPAIRTRTRTRTREIATBPAIRPAIRPAIRPAIRTRTRTRTREIATAPAIRPAIRPAIRTRTRTRTREIATAPAIRPAIRPAIRTRTRTRTREIATAPAIRPAIRPAIRPAIRTRTRTRTREIATBPAIRPAIRPAIRPAIRTRTRTRTREIATB上海交通学院计算机大学计算机网路原理mdashmdash第一章光纤时间分配：分钟教学方式：讲授教学内容：Fiberopticcable:‰glassfibercarryinglightpulses,eachpulseabithighspeedpointtopointtransmission(eg,Gps)owerrorrate:repeatersspacedfarapartimmunetoelectromagneticnoise‰highspeedoperation:‰l上海交通学院计算机大学计算机网路原理mdashmdash第一章重点：光纤的特性及适用范围．无线电波单膜、多膜光纤的特征及适用范围室外、室外光纤的构造时间分配：分钟教学方式：讲授教学内容：Physicalmedia:radio‰signalcarriedinelectromagneticspectrum‰nophysicalldquowirerdquo‰bidirectional‰propagationenvironmenteffects:‰reflection‰obstructionbyobjects‰interferenceRadiolinktypes:‰terrestrialmicrowaveeguptoMbpschannels‰LAN(eg,Wifi)Mbps,Mbps上海交通学院计算机大学计算机网路原理mdashmdash第一章‰widearea(eg,cellular)egG:hundredsofkbps‰satelliteuptoMbpschannel(ormultiplesmallerchannels)msecendenddelaygeosynchronousversuslowaltitude范围ISP和主干网分钟networkofnetworks重点：无线信道的特性及适用无线信道和有线信道的异同点时间分配：教学方式：讲授教学过程：Internetstructure:yhierarchicalSPs(eg,UUNet,BBNGenuity,Sprint,ATT),reateachotherasequals‰roughl‰atcenter:ldquotierrdquoITierprovidersalsointerconnectatpublicnetworkaccesspoints(NAPs)Tierprovidersalsointerconnectatpublicnetworkaccesspoints(NAPs)Tierprovidersalsointerconnectatpublicnetworkaccesspoints(NAPs)nationalinternationalcoveragetTierISPTierISPTierISPTierprovidersinterconnect(peer)privatelyNAPTierISPTierISPTierISPTierprovidersinterconnect(peer)privatelyTierprovidersinterconnect(peer)privatelyNAPNAPNAPIntroductionTierISP:eg,SprintSprintUSbackbonenetwork上海交通学院计算机大学计算机网路原理mdashmdash第一章Internetstructure:networkofnetworks‰ldquoTierrdquoISPs:smaller(oftenregional)ISPsConnecttooneormoretierISPs,possiblyothertierISPsTierISPsalsopeerprivatelywitheachother,interconnectatNAPTierISPTierISPTierISPNAPTierISPTierISPTierISPpaystierISPforconnectivitytoTierISPTierISPTierrestofInternettierpror‰tierISPiscustomerofvideISPInternetstructure:networkofnetworks‰ldquoTierrdquoISPsandlocalISPslasthop(ldquoaccessrdquo)network(closesttoendsystems)TierISPTierISPTierISPNAPTierISPTierISPTierISPTierISPTierISPlocalISPTierISPlocalISPlocalISPlocalISPLocalandtierhighertierISPsarecustomersoflocalISPlocalISPlocalISPlocalISPofInternetISPsconnectingthemtorestInternetstructure:networkofnetworks‰apacketpassesthroughmanynetworks!TierISPTierISPTierISPNAPTierISPTierISPTierISPTierISPTierISPlocalISPlocalISPlocalISPlocalISPlocalISPTierISPlocalISPlocalISPlocalISP重点：了解NBP、NAP、ISP之间的关系以及运作模式。

上海交通学院计算机大学计算机网路原理mdashmdash第一章总结：本次课程的主要内容地理介质ISP和主干网上次课程的主要内容：分组交换网的推迟和遗失作业previewquestion上海交通学院计算机大学计算机网路原理mdashmdash第一章第章第学时学时遗失形成推迟和遗失的成因课和后续课的关系：运用数学介质接入互联网的技术这节继续介绍影响网路功耗重要诱因：分组交换网中的数据分组的推迟和遗失要求把握分组交换网的推迟种类和估算方式以及导致分组遗失的成因。下节课介绍理解网路合同的层次结构以及服务模型理解合同的分层结构对于后续几章的学习是至关重要的。主要教学环节：推迟的种类排队推迟和分组遗失互联网的推迟和路由教学内容推迟的种类时间分配：分钟教学方式：提问讲授教学过程：提问本次课计划课时：教学要领：分组交换网的推迟和与前续上节课了解了的一个络上海交通学院计算机大学计算机网路原理mdashmdash第一章Howdolossanddelayoccurbufferspacketarrivalratetolinkexceedsoutputlinkcapacitysqueue,waitforturnpacketsqueueinrouter‰‰packetpacketbeingtransmitted(delay)Foursourcesofpacketdelay‰nodalprocessing:timewaitingatoutputlinkfortransmissionncongestionlevelofrouter‰checkbiterrors‰determineoutputlink‰queueingdependsoABpacketbeingtransmitted(delay)packetsqueueing(delay)free(available)buffers:arrivingpacketsdropped(loss)ifnofreebuffersABpacketbeingtransmitted(delay)packetsqueueing(delay)packetsqueueing(delay)free(available)buffers:arrivingpacketsdropped(loss)ifnofreebuffersfree(available)buffers:arrivingpacketsdropped(loss)ifnofreebufferstransmissionABpropagationnodalprocessingqueueingtransmissionABpropagationnodalprocessingqueueing上海交通学院计算机大学计算机网路原理mdashmdash第一章‰Transmissiondelay:‰R=linkbandwidth(bps)‰L=packetlength(bits)Propagationdelay:‰d=lengthofphysicallink‰s=propagationspeedinmedium(~xmsec)‰propagationdelay=ds以下例子说明推迟的含意Caravananalogy‰Carsldquopropagaterdquoatkmhr‰Tollboothtakessectoserviceacar(transmissiontime)‰car~bitcaravan~packendtollboothrCaravananalogy(more)t‰Q:Howlonguntilcaravanislinedupbefore‰Timetoldquopushrdquoentirecaravanthroughtollboothontohighway=*=sectcartopropagatefromsttondtollboth:km(kmhr)=h‰Timeforlas‰A:minutes‰Carsnowldquopropagaterdquoatkmhr‰Tollboothnowtakesmintoserviceacar‰Q:Willcarsarridboothbeforeallcarsservicedatstbooth‰Yes!AfterndcarsstillatstboothNote:sandRareverydifferentquantities!vetonmin,stcaratboothandtollboothtollboothtencarcaravankmkmtollboothtollboothtollboothtollboothtencarcaravankmkm上海交通学院计算机大学计算机网路原理mdashmdash第一章‰stbitofpacketcanarriveatndrouterbeforepacketisfullyouter!ebsiteNodaldelaytransmittedatstr‰SeeEthernetappletatAWLW‰dprop=propagationdelay‰afewmicrosecstohundredsofmsecs重点：推迟的种类各式推迟形成的成因推迟时间的估算方式‰dproc=processingdelyas‰typicallyafewmicrosecsorles‰dqueue=queuingdelay‰dependsoncongestion‰dtrans=transmissiondelay‰=LR,significantforlowspeedlinks排队推迟和分组遗失时间分配：分钟教学方式：讲授教学过程：Queueingdelay(revisited)‰R=linkbandwidth(bps)‰L=packetlength(bits)‰a=averagepacketarrivalrateproptransqueuedddprocnodaldd=trafficintensity=LaR‰LaR~:averagequeueingdelaysmall上海交通学院计算机大学计算机网路原理mdashmdash第一章‰LaR:delaysbecomelarge‰LaR:moreldquoworkrdquoarrivingthancanbeserviced,averagedelayinfinite!重点:理解流量密度的含意互联网的推迟和路时间分配：分钟由教学方式：提问讲授教学过程：ysandroutesldquoRealrdquoInternetdeladelaylosslooklike:‰WhatdoldquorealrdquoInternet‰TracerouteprogramprovidesdelaymeasurementfromsourcetorouteralongtpathtowardsdestinationForalli:routerionpathtowardsdestinationsmissionandreplyendendInterne‰sendsthreepacketsthatwillreach‰routeriwillreturnpacketstosender‰sendertimesintervalbetweentran上海交通学院计算机大学计算机网路原理mdashmdash第一章ldquoRealrdquoInternetdelaysandroutestraceroute:gaiacsumassedutowwweurecomfrcsgw()msmsmsborderrtfagwumassedu()msmsmschtvbnsgwumassedu()msmsmsnet()msmsmsnet()msmsmsaidedu()msmsmsnycmwashabileneucaidedu()msmsms)msmsmsantnet()msmsmsnet()msmsmsantnet