enhancing transport networks with internet protocols abstract

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1、EnhancingTransportNetworkswithInternetProtocolsAlanChapman,NortelH.T.Kung,HarvardUniversityMarch1998AbstractTransportnetworksarefacingnewchallengesandopportunitiesbecauseoftheexplosivegrowthofdatatraffic.Besideshavingtomeettheeverincreasingbandwidthdemand,transportnetworksneedtoprovidenew

2、functionalitiesforthesupportofdataapplications.Forexample,theyshouldprovideelasticdatapipeswhichguaranteeminimumbandwidthsbutalsoallowexpansionwhenextrabandwidthisavailable.Theyshouldsupportinstantandautomaticdiscoveryandconfigurationoflayer-3nodeswhich,traditionally,ispossibleonlyforLANs

3、.Enhancedtransportsystemswithinherentpacketmultiplexingcanmeetthesechallenges.ItwillbenaturaltouseInternetprotocolsandtechnologiestoimplementthesepackettransportsystems,andtherebyre-usemuchoftheexistingInternetinfrastructurealreadywidelydeployed.IntroductionTransportsystemssuchastheNorthA

4、mericanSONETnetworksarearrangementsofmultiplexers,switches(oftencalledcross-connects)andtransmissionlinksthatprovidevirtual“pipes”betweenservicepoints.Thepipesareadministeredandrelativelystaticandthecomplexityofprovidingthemishiddenfromthehigherlayerservices.Mostofthetrafficcarriedonthetr

5、ansportnetworkwillsoonbedata.Theincreasingproportionofdatatrafficwillrequirethetransportsystemschangetohandledatapacketflowsmoreefficiently,andalsotoworkwellwithfeaturesofdatatrafficsuchashigh-levelend-systemprotocolslikeTCP.Existingtransportsystemsarecircuit-basedandhavedevelopedasawayof

6、efficientlymanagingnetworksbasedonthetimedivisionmultiplexing(TDM)voicebandwidthhierarchy.TheyprovidethesamefixedbandwidthTDMpipesforbothvoiceanddata.Thiscausesinefficiencyfordataapplicationswhichareinherentlybursty.TheTDMhierarchyhasacoarsegranularityathighbandwidthsresultinginunder-util

7、izationandyetdataflowsareunabletoexploittheleftoverbandwidthofotherdatapipes.Asdatatrafficbecomesthedominantloadfortransportsystems,highefficiencyincarryingdataiscritical.Afewpercentofefficiencyincreasecantranslateintoalargecostsavingbyavoidingnewinvestmentorbycaptu