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基于opnet的TCPVeno性能研究和仿真.docx

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基于opnet的TCPVeno性能研究和仿真 Introduction TCPVenoisacongestioncontrolalgorithmthatwasdevelopedtoprovidebetterperformanceunderacertainsetofnetworkconditions.ItwasdesignedtobeanimprovementontheexistingTCPRenoalgorithm,whichhadbeenthedefactostandardformanyyears.ThepurposeofthispaperistoexaminetheperformanceofTCPVenoinasimulatednetworkenvironment,usingtheOPNETsoftwarepackage. Background BeforediscussingTCPVeno,it'simportanttounderstandhowTCPRenoworks.TCPRenoidentifiescongestionbyusingatimeoutorbydetectingthreeduplicateACKs,whichareindicationsthatapacketmayhavebeenlostintransit.Whencongestionisdetected,TCPRenoperformsabinarysearchtodeterminethemaximumwindowsizethatcanbeusedwithoutcausingfurthercongestion.Thisapproachiseffectiveinmostsituations,butit'snotalwaysefficient.Inparticular,whencongestionoccursinanetworkwithalargebandwidth-delayproduct(BDP),TCPRenomaynotbeabletoachieveoptimalperformance. TCPVenowasdevelopedtoaddressthisproblem.Itusestwomechanismstoachievebetterperformance:abandwidthestimationalgorithmandacongestioncontrolmechanismbasedontheestimatedbandwidth.Thebandwidthestimationalgorithmisusedtoestimatetheavailablebandwidthofthenetwork,takingintoaccountboththecurrentcongestionlevelandthesizeofthecongestionwindow.Thecongestioncontrolmechanismthenadjuststhecongestionwindowsizebasedontheestimatedbandwidth,inordertoachieveoptimalperformance. Methodology ToevaluatetheperformanceofTCPVeno,weusedtheOPNETsoftwarepackagetosimulateanetworkenvironment.Thenetworkconsistedofasinglesourcenodeandasingledestinationnode,witharouterinbetween.Wevariedthebandwidthanddelayofthenetworktosimulatedifferentnetworkconditions,andmeasuredtheperformanceofTCPVenoundereachcondition.WealsocomparedtheperformanceofTCPVenowiththatofTCPReno,toseehowtheydiffered. Results WefoundthatTCPVenoperformedbetterthanTCPRenoincertainsituations,particularlywhenthebandwidthdelayproductwashigh.Undertheseconditions,TCPRenowasunabletoachieveoptimalperformance,whileTCPVenowasabletomaintainahighdatatransferrate.However,