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1、AComparisonofafewSimpleMulticastSchemesforDe
ectionNetworksW.OlesinskiandP.GburzynskiDepartmentofComputingScience615GSB,UniversityofAlberta,Edmonton,AB,CanadaT6G2H1tel:(403)492-2347(oce),(403)492-1071(fax)e-mail:[wladek,pawel]@cs.ualberta.caURL:http://www.cs.ualberta.ca/~[wladek
2、,pawel]Keywords:de
ectionnetworks,multicast,performance,simulation.AbstractMulticastinginde
ectionnetworksismoredicultthaninstore-and-forwardnetworks,becauseofthedicultiesinsendingmultiplecopiesofthesamepacketonseveraloutputports.Ontheotherhand,de
ectedpacketsstrayfromtheiropti
3、malpathsandmayvisitthemulticastrecipientsaccidentally,"notnecessaryintheorderenvisionedbythesender.Wecompareanumberofnaturalmulticaststrategiesforde
ectionnetworksbasedonafewsimplerulesandassumptions.Inparticular,weneverbuerpacketsthatcannotberelayedimmediately.1IntroductionWec
4、onsiderpurede
ectionnetworks
5、onesthatneverlosepacketsbecauseofalimitedbuerspace.Packetsthatatthemomentofarrivalcannotberelayedviatheirpreferredroutes(becausethoseroutesarebusy)arede
ected,i.e.,relayedviasuboptimalroutes.Thisconcept,traditionallyillustratedbytheManhattan-streetne
6、tworks(MSN)introducedandanalyzedbyMaxemchukin[6,7,8,9,10],worksundertheassumptionthattheamountofbuerspaceavailableataswitchissucienttodeterminetheroutepreferenceofanincomingpacketbeforethepacketisrelayedviaoneoftheoutgoinglinks.Nobuerspaceisrequiredforstoringpacketsthatcannotb
7、eimmediatelyrelayedviatheiroptimalroutes,althoughitmaymakesensetostoresuchpacketstemporarilybeforede
ectingthemrightaway[7].Inade
ectionnetwork,asourceconnectedtoaswitchmaysenditspacket,onlyifatleastoneincomingslotisempty.Inaheavilyloadednetwork,manyslotswillbenon-emptyandthesour
8、cemaynotbeallowedtotransmitthepacketimmediately.De
ectionnetworksaregoodcandidatesforhigh-speedMANs.In[1]and[12],wearguethattheirperformanceforsynchronousandisochronoustracmaybequiteacceptable,despitetheapparentunpredictabilityofroutes.Oneimportantfeatureofacontemporarynetworkis
9、themul-ticastcapability,widelyusedinmany