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1、SCALABILITYINIP-ORIENTEDNETWORKSScalabilityandQualityofService:ATrade-off?MichaelWelzl,LeopoldFranzensUniversityofInnsbruckMaxMühlhäuser,DarmstadtUniversityofTechnologyABSTRACTmorefacultymembers.Asalogicallayerbetweenstudentsandus,thetutorsaggregatedDuringthelast
2、decade,twobigeffortsonthequestionsandbroughtthemtous.Ourser-Internetqualityofserviceweremade.Thefirst,vicehadacoarsergranularity,but,fromourper-IntServ,promisespreciseper-flowserviceprovi-spective,thenumberofstudentswehadtosioningbutneverreallymadeitasacommer-com
3、municatewithwasreduced.Thetotalsystemcialend-userproduct,whichwasmainlyworked—itwasscalable.Notably,thequalityofaccreditedtoitslackofscalability.Itssucces-serviceexperiencedbyindividualstudentssuf-sor,DiffServ,ismorescalableatthecostofferedbecausewecouldnotanswer
4、eachques-coarserservicegranularity—whichmaybethetionpersonally.reasonwhyitisnotyetcommerciallyavailableAsimilarthinghappenedontheInternet.Totoenduserseither.Thisleavesuswiththestaywithourmetaphor,earlyqualityofservicequestion:isthereafundamentaltrade-off(QoS)prov
5、isioningconceptssimplyassignedbetweenQoSandscalability?Atrade-offthat,somestudentsahigherprioritythanothers;inthelongrun,couldpreventdeploymentofthesestudentswouldobtainbettertreatmentQoSforendusersaltogether?frommycolleagueormyself(e.g.,whileotherswouldonlybeall
6、owedtopayusavisitatspecif-SCALEVS.SERVICEicofficehours,questionsfromthesestudentswouldbeansweredatanytime).DependingonTwoyearsago,Iwasfacedwithapeculiarsitu-thenumberofhigh-andlow-prioritystudents,ationattheUniversityofLinz:Iwasoneofthismethodmayormaynotyieldanac
7、ceptabletwofacultymemberswhowereinchargeofservice;sincethequalityoftheservicedegradesteachingapproximately300studentshowtoinalinearmannerasthenumberofstudentswritesimpleprogramsinJava.With150stu-grows,theprocessobviouslydoesnotscalewelldentsforeachofus,thiscouldh
8、avebecomea(Fig.1).severeproblem:bydefault,eachofthesestu-Thenetworkcounterpartofourstudentsdentsfeltthatweweretheoneswhowouldbeingend-to-endtrafficflows(source
