Performance Analysis of Reactive Congestion Contro

1、PerformanceAnalysisofReactiveCongestionControlBaseduponQueueLengthThresholdValuesM.KatoaY.OiebM.MuratacH.MiyaharacaDepartmentofElectronicsandInformationEngineering,AriakeNationalCollegeofTechnology,Omuta,836JapanbInformationTechnologyCenter,NaraInstituteofTechnology,Ikoma,630-01JapancDepartmentofInformationandComputerSciences,FacultyofEngineeringScience,OsakaUniversity,Toyonaka,560JapanAbstractReactivecongestioncontrolbasedupontwothresholdsisanalyzed.Underthecongestioncontroltreatedhere,amultip。

2、lexerortransitnodeinthenetworkrecog-nizescongestionwhenitsqueuelengthreachessomepre-determinedthresholdvalue,denotedbyH.Thecongestednodethenexplicitlyinformsthesourcessharingthenodeofitscongestioninsomewaytomarkaforwardcongestionnotiﬁcationbitintheheaderofcellsifprovided,ortodirectlysendcontrolcellstothosesources.Thesourcesthenstopthecelltransmissionaccordingtothefeedbackinformationreceived.Thereliefofcongestionisrecognizedbythenodewhenitsqueuelengthdecreasestosomelow-threshold,L,andinformstheso。

3、urcesthatthesourcescanagainstartthecelltransmission.Inthispaper,weinvestigatethissortofcongestioncontrolbyformingaqueueingnetwork,inwhichmultiplesourcesandasinglenodeareexplicitlymodeled.Throughananalysis,wediscusstheimpactofthosetwothresholdstoperformanceofthecongestioncontrol.Keywords:ATM,ATMLAN,congestioncontrol,reactivecongestioncontrol,explicitcongestionnotiﬁcation,performanceanalysis1IntroductionInbroadbandintegratedservicesdigitalnetworks(B-ISDN),asynchronoustransfermode(ATM)isemployedtoo。

4、ﬀerawidevarietyofservices(forex-ample,data,voice,videoetc).InATMnetworks,congestioncontrolisveryimportantforachievinghighutilizationofthenetworkandguaranteeingtheQOS(QualityOfService)requiredbyvariousservices.CongestioncontrolinATMnetworksisdividedintotwocategories:preventivecontrolandreactivePreprintsubmittedtoElsevierScience9June2000control.InwideareaATMnetworks,preventivecontrolhasbeenemployedbecauseitisrecognizedasamethodtoeﬃcientlytreatcongestion[3].Underthepreventivecongestioncontrol,users。

5、arerequiredtodeclarethecharacter-isticsoftheirtraﬃcinadvanceforconnectionsetup,andthenthenetworkdetermineswhetheritpermitstherequestedcallornot.Afterthecallestab-lishmentrequestisadmitted,theuserisnotallowedtoviolateitsdeclaredtraﬃcparametersduringtransmission.Bythis“traﬃccontract”mechanism,QOScanbeattainedforeachuser.Thus,itshouldbesuitabletorealtimetraﬃcsuchasvoiceorvideoinwhichitstraﬃccharacteristicscanbeknowninadvance.Ontheotherhand,whendatacommunicationsisconsidered,itisnotverylikelythatuse。

6、rsknowthecharacteristicsoftheirtraﬃcinadvance.Amoreimportantproblemisthatinpreventivecongestioncontrol,theusersnevertransmitcellsexceedingthetraﬃccontractevenwhenthenetworkisnotcon-gested.Therefore,itisapparentthathighspeeddatacommunicationisnotachieved.Thus,inATMlocalareanetworks(LANs),anotherkindofcon-gestioncontrolhasbeenstudied,i.e.,reactivecongestioncontrol[5].Underthereactivecongestioncontrol,atransitnodeinthenetworkrecognizescon-gestionoccurringbydetectingthatitsqueuelengthreachessomehigh。

7、-levelthresholdH.Thecongestednodetheninformsthesources,whichsharethelinkofthatnode,inoneofthefollowingtwoways.Thenodemarksaforwardcongestionnotiﬁcationbitintheheaderofcellsifprovided,andthosecellsarriveattheirdestinations.Eachdestinationtheninformsitscorrespondingsourceofthecongestionbymarkingabackwardcongestionnotiﬁcationbitofthebackwardcells.ThistypeofcontroliscalledFECN(ForwardExplicitCongestionNotiﬁcation)basedcongestioncontrol.Analternativeapproachisthatthecongestednodegeneratesanddirectlys。

8、endscontrolcellstothesources,whichiscalledtheBECN(BackwardECN)basedcongestioncontrol.Thereliefofcongestionisnotiﬁedwhenthequeuelengthdecreasestosomelow-levelthreshold,L.Notethatthesetwowaysarediﬀerentonlyinthedelayexperiencedbyfeedbackinformationinthecurrentstudy.In[1,2,4,7],reactivecongestioncontrolshavebeenstudied.Kawaharaetal.haveanalyzedin[7]theimpactofburstytraﬃctotheperformanceofthereactivecongestioncontrolwhereasthelow-levelthresholdvalueisﬁxedatH−1.Ontheotherhand,Wangetal.[1]haveanalyzed。

9、thereactivecongestioncontrolbasedupontwothresholds.However,cellsareassumedtobealwaystransmittedaccordingtoaPoissondistributioninavailableslotsfromeachsource.Referto[7]forotherrelatedstudies.Inthispaper,wedevelopaqueueingnetworkmodeltoanalyzethereactivecongestioncontrolbasedonECNschemesdescribedabove.Ourmodelisde-velopedinawaytoextendthemodelof[1]totreatmorerealisticcaseinwhicheachsourceisequippedwithbuﬀerstostorecellswhenthecelltransmission2isprohibited.Furthermore,themodelenablesustodiscussthee。

10、ﬀectoftwothresholdsontheperformanceandalsotoevaluatetheamountofcontrolcellsrequiredintheBECNscheme.Theremainderofthispaperisorganizedasfollows.InSection2,wedescribetheanalyticalmodelandthereactivecongestioncontrolschemeconsideredhere.Section3presentsouranalysisofthereactivecongestioncontrolandthederivationofthecelllossprobabilityandtheaveragecyclelength.InSection4,wediscusstheperformanceofthecongestioncontrolthroughnumericalresults.Finally,Section5summarizesthepaper.2ReactiveCongestionControlSche。