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1、CharacterizingSessionInitiationProtocol(SIP)NetworkPerformanceandReliabilityVijayK.Gurbani,LalitaJ.Jagadeesan,andVeenaB.MendirattaBellLaboratories,LucentTechnologiesNaperville,Illinois{vkg,lalita,veena}@lucent.comAbstract.TheSessionInitiationProtocol(SIP)hasemergedastheprefe
2、rredInternettelephonysignalingprotocolforcommunicationsnetworks.Inthiscapacity,itbecomesincreasinglyessentialtocharacterizeboththeperformanceandthereliabilityofthesignalingentitiesutilizingtheprotocol.WeprovideananalyticallookattheperformanceofaSIPnetworkaswellasareliability
3、modelofSIPservers.Keywords:SIP,StochasticProcesses,QueueingAnalysis,PerformanceAnalysis,ReliabilityAnalysis.1IntroductionThePublicSwitchedTelephoneNetwork(PSTN)hasevolvedoveracenturytobecomeanintegralpartofhumancommunications.Overtheyears,thenetworkhasbeentunedforperformance
4、andhasevolvedtobecomehighlyreliable,withindividualswitchesexperiencingonlyafewsecondsofdowntimeperyear.Asthetelecommunicationsindustrymovestowardsanewnetwork(theInternet)withanewsetofsignalingprotocols,mediabehaviorsandroutingprotocols–whicharemarkedlydifferentfromthePSTNmod
5、el–isitreasonabletoassumethattheperformanceandreliabilitymetricsestablishedinthePSTNareapplicableandachievableinthenewenvironment?Performanceanalysisandreliabilityofcircuit-basedcommunicationnetworkshasbeenwellstudied.ModelsexistinthePSTNthatcharacterizeperformanceintelecomm
6、unicationswitches.OnemeasureofperformanceinthePSTNistheBusyHourCallAttempt(BHCA)metric,whichisdefinedasthenumberofcallattemptsduringthebusiesthouroftheday.TheBHCAmeasuresthecapacityofaPSTNcallprocessingswitchintermsofthetotalnumberofcallsarrivingataswitchduringpeakperiods.In
7、commercialPSTNswitches,itrangesfrom1millionto2millioncallsperhour.Anothermeasureofperformanceistheswitchcross-officedelay,whereatypicalvalueis100-300milliseconds(ms);thepreciserequirementsforthismetricarespecifiedbysignalingmessagetype.Circuitswitchesforvoicemeetstringentreq
8、uirementsforreliabilitywithexpectedswitchavailabilitygreaterthan0.99999ande
