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1、©2003IEEE.Personaluseofthismaterialispermitted.However,permissiontoreprint/republishthismaterialforadvertisingorpromotionalpurposesorforcreatingnewcollectiveworksforresaleorredistributiontoserversorlists,ortoreuseanycopyrightedcomponentofthisworkinotherworksmustb
2、eobtainedfromtheIEEE.SCALABILITYINIP-ORIENTEDNETWORKSScalabilityandQualityofService:ATrade-off?MichaelWelzl,LeopoldFranzensUniversityofInnsbruckMaxMühlhäuser,DarmstadtUniversityofTechnologyABSTRACTmorefacultymembers.Asalogicallayerbetweenstudentsandus,thetutorsag
3、gregatedDuringthelastdecade,twobigeffortsonthequestionsandbroughtthemtous.Ourser-Internetqualityofserviceweremade.Thefirst,vicehadacoarsergranularity,but,fromourper-IntServ,promisespreciseper-flowserviceprovi-spective,thenumberofstudentswehadtosioningbutneverreal
4、lymadeitasacommer-communicatewithwasreduced.Thetotalsystemcialend-userproduct,whichwasmainlyworked—itwasscalable.Notably,thequalityofaccreditedtoitslackofscalability.Itssucces-serviceexperiencedbyindividualstudentssuf-sor,DiffServ,ismorescalableatthecostofferedbe
5、causewecouldnotanswereachques-coarserservicegranularity—whichmaybethetionpersonally.reasonwhyitisnotyetcommerciallyavailableAsimilarthinghappenedontheInternet.Totoenduserseither.Thisleavesuswiththestaywithourmetaphor,earlyqualityofservicequestion:isthereafundamen
6、taltrade-off(QoS)provisioningconceptssimplyassignedbetweenQoSandscalability?Atrade-offthat,somestudentsahigherprioritythanothers;inthelongrun,couldpreventdeploymentofthesestudentswouldobtainbettertreatmentQoSforendusersaltogether?frommycolleagueormyself(e.g.,whil
7、eotherswouldonlybeallowedtopayusavisitatspecif-SCALEVS.SERVICEicofficehours,questionsfromthesestudentswouldbeansweredatanytime).DependingonTwoyearsago,Iwasfacedwithapeculiarsitu-thenumberofhigh-andlow-prioritystudents,ationattheUniversityofLinz:Iwasoneofthismetho
8、dmayormaynotyieldanacceptabletwofacultymemberswhowereinchargeofservice;sincethequalityoftheservicedegradesteachingapproximately300studentshowtoinalinearmannera