telemedia networks and systems group

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1、TheACTIVEIPOptionDavidJ.WetherallandDavidL.TennenhouseTelemediaNetworksandSystemsGroupLaboratoryforComputerScienceMassachusettsInstituteofTechnologyAbstractInthispaper,wediscussourworkonanactivenetworkarchitectureinwhichpassivepacketsarereplacedwithactivecapsules

2、encapsulatedprogram

3、fragmentsthatareexecutedateachswitchtheytraverse.Thisapproachallowsapplication-specicprocessingtobeinjectedintothenetwork.Theaccessibilityofcomputa-tionandstoragewithin"thenetworkprovidesasubstratethatcanbetailoredtobuildglobalapplications,includingthosethatinvokecustomizedmulticas

4、tandmergeprocessing.WedescribeanextensiontotheIPoptionsmechanismthatsupportstheembeddingofprogramfragmentsindatagramsandtheevaluationofthesefragmentsastheytraversetheInternet.TheactiveoptionprovidesagenericapproachtotheextensionoftheIPnetworkservice.1ActiveNetworksTraditionaldatanetw

5、orkspassivelytransportbitsfromoneendsystemtoanother.Ideally,theuserdataistransferredopaquely,withtheroleofcomputationwithinsuchnetworksbeingextremelylimited,e.g.,headerprocessinginpacket-switchednetworksandsignalinginconnection-orientednetworks.ActiveNetworks[TW96]breakwithtraditionb

6、yallowingthenetworktoperformcustomizedcomputationsontheuserdata.Forexample,auserofanactivenetworkcouldsendacustomizedvideotranscodingprogramtoanodewithinthenetwork(e.g.,arouter)andrequestthatthenodeexecutethatprogramwhenprocessingtheirpackets.Thesenetworksareactive"intwoways:switch

7、eswithinthenetworkperformcomputationsontheuserdata owingthroughthem;individualscaninjectprogramsintothenetwork,therebytailoringthenodeprocessing.InteroperabilityTraditionalpacketnetworksachieveinteroperabilitybystandardizingthesyntaxandsemanticsofpack-ets.Internetroutersallsupportth

8、eagreedIPspecications;althoughrouterimplementationsmaydier,theyimplementequivalent"programs.Incontrast,activenodescanexecutemanydierentprograms.fdjw,dltg@lcs.mit.edu.http://www.tns.lcs.mit.edu/Interoperabilityisachievedatahigherlevelofabstraction

9、insteadofstandardizingthecomputa

10、tionper-form