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1、v1.0可编辑可修改华南理工大学计算机网络复习资料Network Topology:Layout of inter-connections （信道的分布方式）CH1.IntroductionWhotisComputerNetworks1BasicConceptofComputerNetworks:-AcaKectianofautonomouscomputersintetconnected.hkeroofmected：Beableroexchangeiflf&rmahon,AuDnDmojs:3cctictohandleindependently31LocalAreaNetworksOperat
2、emU】I”alimdeugecgraph杷jreaAhuwmullidccvtLuhigh-bdiidwidlhrnedidControlthtprival*lyundrlocalZEiniKtritiofiProvidefjli-timtconntirtyI。localmivpc+slConnie!y.irijarpniripvirpWideAreaNetworksrANsaredesignedto:OperateeverlargegHgraphlcalareaAllev/acctitov*ri2linlftffacatoperatingitloinrrfpAcltPmvtd且Tull-t
3、E*andpmrt41nl电c4nnftvHyCQnnvctcvrwidt.v*nglobalaz*CommunicationMode:Point4o-PointMulticastBuTofKilogyRinfjTopolQQryStarApplicationPresentationSessionTransportNetworkNetworkDataLinkPhysicalHirtrchicttTffPt（gyTbcralogyExWndedStwrTpualcgySessionITransportDataLinkPhysicalHostAHostBApplicationPresentatio
4、nfnmi BroadcastProtocolisthemostimportant!OSImodel5 Interhost communication 1 Binary transmition Wires, connectors, voitiges7NetworkprocessestoapplicationsPrwidesEwortceeiviceslnprocesses(suchdecfrunicmiI,filetransfer,andterminaletnukliun)6DatarepresentationInsured1aisftswdblebyreceMngs/stdnFOfTTWto
5、fdtft*。温dstnjctuFesdal4iuanferNd*forApplicationJayerEsUhksnes*rwn4qeK,&ferminatecveonbetweenappticdfttons3AddressesandbestpathProvidesconnectivityandpathsdecttnnhetwnentwoendsystemsDomainofroulinQ2Accesstomedia ProvidesieiidbietranferofcUt电across Physical4ddrHingTcGvmo山lopolowemoinE而cstkm.flowcontro
6、ldatanites4 End-to-end connections C onccmed *wfth dla trnpt imsuh betwmi End 患 Dta tnnaport 宿 ftcrnitidlvvihu*l cirturts* F *ult drtncfion and nxnwsy InfDfnutwm Dow comol Reducescomplexity Standardizesinterfaces Facilitatesmodularengineering Ensuresinteroperabletechnology Acceleratesevolution Simpl
7、ifitachingandkarningEncapsulation/de-encapsulation/TCP/IPmodelFourieSeries Any reasonably behaved periodic function, g(t), with period T can be constructed by summing a (possibly infinite) 口umber 0f 与ine and coine：CH2.PhysicalLayerBitRatevs.Harmonicsbitrateofbbits/secsend8bitstimeT-8/bsecf=1/T=b/8nf
8、crofbitsofatransmissionmediumiscalledbandwidth.NyquistsTheorem(noiselesschannel)-H:bandwidth-V:discretelevels-Maximumdatarate:2Hlog4Vbits/secShannontheory.%=，0喻目卜力N5McixDataRate=/logJ1+一)bits/sec Threemajortransmissionmediaarewidelyusedtoday:twistedpair,coaxialcableandopticalfiberExercisesolution Su
9、pposethatthebandwidthofachannelisbetween3MHzand4MHzandSN=24dB.g-(1)whalisIhemaximuLiidatarate? H=iMH? S/N=351 C=+251)=8Mbps(2)Beingabletoachievecapacity,howmanysignalinglevelsarerequired?*C=NHlo及VI奈米,隹根桐I线以螺前伏时用式求愤地镣门 乳.喻像 个DRA舒用 上所以林制根 调”酣缱在国国为两幄平忖的城会构成个晌大缝“，睛根域的在 黑厄.不 H电线产生的扰波史招汇掩涧,从而也“鲁啤/电鬻的*th点号
10、施带以两辕也线的电 伍整未承爨，这样对外部嘤立有变”的免嵯力.因为事声对两框由空的扰是相同的.W 它们的电田，却不余可变.UTPvs.STPandCOAX-advantages.- Itiseasytoinstall- islessexpensive- itsrealadvantageinitssize.disadvantagesismorepronetoelectricalnoiseandinterference-onceconsideredsl*werattransmittingdatathanothertypesofcable.today,irn*isconsideredthefaste
11、stcoppe”basedmedia.ThedistancebeHveensignalboostsisshorterforiinriii磔dedtwisted-pairthanitisforcoaxinlcable.V=j6Twistedpair*UTP(UnshieldedTwistedPair)*STPShieldedTwi5t巳dPair)Inpractice3fiberrequiresanactiverepeaterevery30km.copperevery5kmWireless TransmissionWave PropertiesRadio Transmissionshines)M
12、icrowave TransmissionMicrowaves-travel in straight lities* cati be narrowlyfnci.i8?fi (by n dish)* the transmitin and nxicivinx :interm；is nnwt be accurately aliened with each otlnbr.-do not pass through buildings well.-can be absorbed by water/rain-widely used for Inng-distance telephone eoniinunic
13、ation, cellular telephones, TV distributionInfrared and Millimeter Waves widtlv used Ibr slitM L-iaEigc conitTiLinication.-rlV reuiole、,口ntrolMr do not puss through solid ulyueh.-Bad: limited distance-GjkI: security candidate for indcor vrirckss I-AN* can nut be ustxl outdiHirs du 匕 to suit TheElect
14、romagneticSpectrum RadioTransmission,MicrowaveTransmission InfraredandMillimeterWaves LightwaveTransmissionJV,X-rays,andCrammaRayswouldbeevenbetterduetotheirhigherfrequencies-hardloproduceandmodulate-donotpropagateivellthroughbuildings-dangeroustolivingthingsRadiowaves-easytogenerate-cantravel加此dist
15、ances-piinetriiti1buildingse Endi side net* 恢 its own lasers nd its own pho lodelector. The laser s strength, a verv narrow bciim, is its wvtiknexs.-difficult aiming st for distancE offers hih bandwidth easy to install心ily-omnidiructional-atlowfrequencies,thepowerfallsoffsharplywithdistunecfiotnlhex
16、ourcr-alhighfrec|iiencieshradiowavestendtotrflvelinstraightlinesandbnunceoffobstuclrsLightwaveTransmissionPSTN(PublicSwitchedTelephoneNetwork)Transmissionlinessufferfromthreemajorproblems：Attenuation-Delaydistortion-NoiseBasicEncodingTechniquesDigitaldataioanalogsignalAmplilude-shiftkeying-Phase-shi
17、ftkeying(PSK),Phaseofcarriersexualshiftedquadraturephase-shiftkeying(QPSK四相/正交相移键控)利用四个相位090”辰示2个加1QAM-64(QuadratrueAmplitudeModulation正M幅度调制-64)DigitalSubscriberLines(DSL)Afixedtelephoneusingawirelesslocalloopisdiffergmfromamobilephoneinthreeways:-ThewinolcsslocalGusltMueroftenwant&high-speedIntcrn
18、elconnectivity.- AdirecUordlaiilennaisneedstobeinstalled.- TheuserdoesnotmoveInFDM(FrequencyDixdsionmultiplexing),thefrequencyspitlruniisdividedintofrequencybands.Furfiberopticchannels,WDM(WavelengthDivisionMultiplexing)isused.InTDM(TimeDivisionMultiplexing),theentirbandwidthisusedforachunkoftimeper
19、iod.DPCM(DifTcn!ntiulPlusCodeModulation)c=bxbg2nC：bitratetB：baudrate：n：discretelevelsTheMobileTelephoneSystemFirst-GenerationMobilephones：AnalogVoiceSecond-GenerationMobilePhones:DigitalVoice* IhirdCcncrationMobilePhones:DigitalVoiceandDataTypesofsatellitesGEO(istntionaryEarthOrbit)satflHtvsSwitcnin
20、q* (irniitswitchinKseek仆白1itpHicdlpitthfnnnridertoreceiver.Anend-to-endpnthmuktbe(conceptually)csTablishedbeforerlntaissent.* Messfl片年svitchiiifi-nopathisestablishedinadvnncp.IhemessageisstaredinthefirstswitchingofficeandtbnvardedlateronthopatatinirExumpk：stDrv-and-fitantinerYr。#-IfWrE：Nnrrstrirtinr
21、ofhlnckPncketKwitrhingplacearvtriilHmnnb1(w:ktriiillntvpnrkffiecr-Athunl工出二WNIt而iZfiMifnwiwQruflk*IrrpngvEtig-nwtHmtuhpil:LEO(LowEarthOrbit)satellitesCDMA:CodeDivisionMultipleAccessA.00011C11：0a1o111oC010111DOD：D10O1la%t-it-i+it+r7；(*t-i+t-i+i+1+i-nc；(-1+1T+1+1+1TfD：(-1+1-1-1T-1+1-1)Skexa/nCQS(1*1H*
22、1T*1*1*1卜8112+0+0钟+2+23+2心=01+1*3S*1-1+1-1MO=1(4T+2+0+2+0-2+2=142-29-2*Q-2-4。|用-1Sl=(-1+1T+1+1+13；-Z00。*2*3包=。a-2+2OF2S.+1+1=3*341-1瓦T0：Q+QIIPfcrtIrJIf132-120一*卜100-124(a)Binarychipsequencesforfourstations(b)Bipolarchipsequences(cSixexamplesoftransmissionsCH3.DatalinklayerMainFunctionsofDLLProviilea
23、welkdefinedscnicvinterlacetothenetworklayer.1苜】withtFHnniissionerrors. Kculutctheflowuf4。llmlreceiversarenotsivmrun-里igjheframe与ThataretransmittedoverthephyKicalliijtcr.Theuseofermr-corrwNnrodoKisoftenreferredtoa号forwarderrorcrrecilon(lf向纠错).Theerror-drlevtiiiganderror-corrcctinKpropertiesofacodedep
24、end(hiilsHammingdisiaiicc. Inordertodetect(*err。】，*weneedadistanceofd+L nordertocorrectderrors,weneedadistanceof2dTirrrtiijwhOHle傅urdV0111UUU1M,queMiut)li：ll瞳inkhturrwi事Lmnrrei TliteifllihlSSf-LmH.vimiik CcmUr：14+5=1L7+尸+1W2 UttUtt)thanitethehitrrmVttoI,CharactercountUs(ssaHeldintheheadertospecify1t
25、henumberofcharactersinthefhimc(SecFigure3,4(abFlagByteswithbytestuffingFlagByteswihbitstuffingXKheneverthesenderdatalinklayerenmujih?1八tconsecutiveKinthedata,itdUTonmticalhstuffsa0bitIntotheMiloingbitstream.PhysicallayercodingviolationsOnlyHppliciibhrlitnuluiin抑hid*tbverKudin(;nnthephdenimeiliuinran
26、tainssmngredundancy.CRC（CyclicRedundancyCheck,循环冗余校验码）CRCThetnsic|dnnfth?CRCmMbod: Ihi1KeiidL?rundrwiherjgrtuupimuiiLiicntlnrpftKnoniiuL（RtkinacKati. Thelitnderuppcndschecksumtvthvendofiherrmnvinsuchuwuythu（thi1pdyiiumiulnprcsriilcdttiethccksumiiiedframeiiliiitkb、GitJ. WhenTherccehrrrh,rheframeitri心
27、4diviriinuitbthesdinvG（k）*】lh#innurriiuindvi.ttbervtn。虱haschcenanerrorandirftran*missionv*illbereqiiH.Protocol1（utopia,乌托邦）DatatrailsmittvdinimkdirectiononlyBoththeTranmitrinEandreceivingnt*（worklayersareuImuysnudy（随时待命）口Pn“心管咤limen*nEh，iynnrfd（瞬间完成）口hiHnitebulTprisavailabte（无隈空间）rhecommunicationcha
28、nndbetweenthedatalinklayerneverorlosesofframes（完美通道）Protocol!SimplexStop-and-WaitProtocol发送方太快,以就接收方忙不过来.解决，按我方返何确认帧链路要姥辛系开1：的Protocol：SimplexProtocolforaNoisyChannelPositiveAckiiowfledgpnwiitwithRetrasmissionXuhinijlicR心nHjillllP2(lfl发送者有个timer,超时则歪传为了避免确仄帧丢失/量复传输.加入了帧序号.Protocol4：n=1basicideaofsli
29、dingwindowpiggybacking(捎带确认)窗口大小=1, channelcapacityisbbp号 fniiuvsizekbits round-trippropafiontimeRsecLineUtilizationRate二k(kbR)Increasemaximumsliding-windowsizeW:Lineutilization-W*T/(Ty+R|=U*k/(k+hR)Protocol6：SelectRepeat(选择性重传)W二(MAX_SEQ+l)/2tJnoEMMidinM计hidoM(p门H“cul4): (I=sizeofSendingwiiidowrWit
30、hFDM，二NT,效率极差，静态分配不好DynamicChannelAllocation5keyassumptions:LStationModeJ匕SingleChannelAssumption3.C4EHsionAumption%CoiUirw。向SlntledTimeSChrriier/NoCurrierSensePersistent CSMA (1-persistent) (nsTir conthiuaily)Advantage： Khwtcr delay than nun-pervistentprobkm： if 2 or more stations are wait at the s
31、ame time, oncePurALOHADangerousperiodofcollisionTimelength：2iGtJivraiedfraniv(mcaii)t21；口ProbabilityofnocolHsion；Po=eThroughput：S=G=Ge-2i口 Slotted ALOHA 旧曰)thechannelbecamtsidle,thetollisinnisluirivoidnbk.Frumc-iimurVIsdiscretvintervulhflngcroufiperkidiifcollidon：eithroughputtS=(randomtime,maybenoda
32、taLttransmitted)CSMA/CDchannelcanbinoneofthreestatesConteiidonTrartsiriiiimidleABit-MapProtocolBinaryCountdownlch conteitfidn period 0f 、Hot褊 nith oneqlot time bdn al leiistIf station i (K= !2匚l)h(huntuerimpriurU)BCon帕ntiMsqURCOLEAYOR Eflicitnqisid/(d+lu；i) Iffirstfirhloffrnminldrcs.thenBitlinn-Limi
33、ted-ContentionProtocol二WhnnJuwkm。,useconknlion,ennreduct，概率delayWhenhihload,usecontention-free,caniinarvFxoanentinlBackoffAfterithcollisioniWhunOviWlO.21-1)X2tiWhen10i16,giveupsendinggethighlint-utility(cOkitHcy)Localinternetworking1floodingalgnrithnij泛洪)bridgebackwardiciirriin(逆向学习)Porttimedomainre
34、flectometry(时间域反射计)Send口”加Timingthfintervalhctwccnendingandrecehing(heechoizethroriginoftb(echoinrr rCin|黜 modingOrdinan；iddnththigh-ftrderbitvalueisQ.Multicusiddilres:thehigh-orderbitvalueb1.BiuAdmuadfiros:allhitshavenvaliwnfl. LochLaddress:assignedbylocalnch*orkadministrator,dKtinguisht?dh,tbeseco
35、ndhighTirderbit(46value04Ferbit47,1)*iinlrsfuliimuddrwxiabuuv7Id11):assignedbyIEEEtovnsuievineldwideuniqiKnEx、*dhtinuishdb)(hrwrimdhh-orderbJi(46)vulurLMACAddress=ManufactureID(川lOrmlMiUaiillyUniqueIdffllificr)+NICD=24tit+24titLnI)1X,the【m(kid$u?cificwhichnzljurk-le、cprocesstogivtheframeto(fbrsuppor
36、tingmulti-prulocoh:ilneturk-layer).()PrcwmbkofSbjMchwithrhrNrpatterninIEEE8023,thMi:nthfieldisthelengthofth(Foriichrunku(IonbetevnIhtsenderiuidlherccrlviT,dat.fiddtb)Rrtunitilcof7bksaSluiloffritme1SOF)bvte,.-；._,Lr，Anynumberinthefieldlesnretiuakto1536(h6IMIconlHimnuIHIUlOlt1udrnoteHirMJtHufheanditil
37、_1.m-J,canbaii3LOBtotakemortthan2tinlime；CH5.NetworklayerMainfunctionis:transportpacket)fromsourcetodestinationalltheway.P343StructureofcommunicationsubnetVirtual-circuitsubnet Selectfipathwhenconncctitmisestablished Exthpackethas曲connection-number ConnectionisrrmovedwhencommunicationisDatagramsubne
38、t EachdalaramhasdeslinMtion-addrrss EachduhigramlookforpjifhindependentyRoutingtableentrythatisconfiguredhyadministratoriscattedstaticroutingRoutingtableentrythati号obtainedbyroutingoratficoliscalleddvnamicrmitinpClassificationofroutingalgorithmDijkstraalgorithmstepsJI(*,V)若与接连接0(V)=t8指廿与f小包接相连Z.look
39、foranodehicbisnotincludedincollectionwbobeD(h)ihlesit,andputintoN;Thunforallnodeswhichorcnotincludedin、usingminD(vUw)+Mh,、)|torrphccDvtDfv)minD(v),D(w)+l(w,v)Flooding(i/2)股二；itr)irjcominL；packetmientoutonI%，ervDQrunjntjtineeweptHimon*itarrisfdcm1不计算踏径，有踞就走A4dEnterinp4ckilhrMcrreduce1whenpu/nnMnpacke
40、thdhcMtdednhrilciuliterkzviv值描n*dfsetaptFtHt”tabMpukviisdlwardvd件henitirrivrsaMCklainHhiodjiij*、也四对* Static algori thin (nor self-adaptive) Dynamic algorithm ( self-adaptive )disHdiluplkalrpuckehurcImuiiujbtImiididlhachantagEfrcliahilihhigh*pathshortsuseinmilitanAfTAir5frequentlyDistoncaVectorRoutin
41、g门人-J距离矢:量路由选择：opcrulch?1】叫|甲Ehrnutermaintainariehasector)givingThebestkttotkdisiuncttueachi注、iMaliui】andv4dehlinv1usktnji?tthere1WorkingprincipleofDV(contd)LinkStateRoutingTheideabehindlinkstateroutingconsistsoffiveparts:D除,口vpr计工npiohhorsHndtcrntheirnrtunrkaddresses. Mensurethed曰小orcosttueachofits
42、ndglibor Constructapuc&ettUling1Jithasjuslkunitd. Sendthispackettoallotherrouters. Computetheshortestpnthtoevenotherroutenrt FitfnrhignehorkDadvantagesEachrvutrrequirebiet，lnr&*T|aceC|nPufing_rkloadisurcarOSPFMessagetypesmsTProblemswiththebasicalgorithm:htbvquenccnumbersinaroundscamsuigConfusion.Sol
43、ution:uwinmnqucnrHmimber.Withonepucktt|Krsiciind,itntmldIlike137yearstowrtparouiuhIfarouterevercrAsheii,itwilllosetrackofitsownqurncenumber,fit“*r抬ag曲inalthebequeocenumber0,Jienpackets琳iUberujeclcdlasobsokte/duplkatebotherrouters.IfaM?quantnumberrvercorrupted浦nd65tM0hreceivedInsteadof4(a1-biTerror),
44、packersS-6sMiIwiHhca，nlnnlefe.00000000000000100lOODOOOOOOOOOOlOO口TheMilutiontoroutercrashesandsequencenmnhercorruptionhfoussdciatvuhh二甘(e.g.60)hhesichsintrpekel布oi】iunvnnitrimddecreirtvnltheHgconcepersecond, Whentheagehitszero,theinformationfromthatrouterisdiscarded. NonniiHynneypacketcotneinei-ery1
45、Usecouds,mirouterinrrmathnnnhtiniernutwhenarvk1c ikstnutlon nHmirk Lmik up iDutini;-t4blv * re-tncup*ulti讣u un( forward Vfain Function Routing l-orward aThrr 172J6.2(k20(J is Class B ddr?ss二 Network portion: 172.16口 Host portion:20J00口 Nctnurk address: 172*16*0.0Broadcast address: 12J6,255,255Conges
46、tionControlvs.FlowControl Itmakessurethesubnetisable加srgJbeofTcredh?flk. ItIsaGlobalissueinvolvingthebehaviorofallth*hosts,洲Mtherouter,tfistore-and-fonsardinprocessingwithintherouters,etc.Flowfon(ro Itrelatestothepoint-to-pointtrafficbetweenagiycnsenderandagenreceiver* Itmake帛surethatafastrendercannotconlinually(ranmitdatafasterthan(hereceiverkabletdabsorbit.AhoMcangetaSlowdon,pniesageeilhrbeEUU学ethereceivercannothandletheloadorbecausethnetworkcannothandleit(confused).虚拟一路子忖的拥蠢控制小njq%iniiinntrnl(准入控制，simplebutcrude)AlternateRouting(绕过问题区域)Vqjutiukanagreementbc
