应用层组播算法研究

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1、中国科学技术大学博士学位论文应用层组播算法研究姓名：李婧申请学位级别：博士专业：计算机软件与理论指导教师：顾乃杰20070501获得了很好的扩展性和路由效率。最后，研究组播服务的QoS保证，提出两种有效的平衡算法PB—B和PB．R来获得流媒体播放连续性和实时性之间的平衡，使端到端延迟和延迟抖动都不超出用户所能接受的限度范围。所提的两种算法PB．B和PB．R都需要利用探测机制获得即时的网络状态，然后根据所获得的信息分别做出相应处理。PB．B引入一个大小可调的缓存，根据即时网络状态对缓存大小进行调整；PB—R引入缓存大小和流速都可调的流量整形器，根据网络状态的变化对缓存大小和流速同时进行

2、合适的调整。两种算法的设计目的都是为了在播放连续性和实时性之间获得较好的平衡，实验表明与经典算法相比，算法PB。B和PB．R在减小网络延迟和减小延迟抖动之间获得了较好的平衡。关键词：互联网；组播；应用层组播；覆盖网络；QoSⅡAbstraetAbstractWithnlerapiddevelopmentofInteract。multicastcommunicationisrequiredbymoreandmoreapplications．1Pmulticastisanativemulticastmeanswhichimplementsmuhicast{nthenet、vorklaye

3、r．However,itsinherentdrawbacksincurtheseriousdeploymentlimitationsofIPmultieast．Inthissituation，application—layermulticastisproposedunderholdingthepromiseforrealizationoflargescaleIntemetmulticastservices．Application—layermulticastissuchadatasttucturethatprovidesmulticastFunctionalityintheoverl

4、aynetworksthroughunicastconnectionsamonggroupmembersintheunderlyinglayers．1ncontrastedtotheIPmulticast．themulticastfunctionsinapplication-layermulticastareimplementedbyendhostsinsteadofintermediaterouters．Thereforethedeploymentiseasyforapplication—layermulticast．However,theresourceandthemultica

5、st{mplementationinthecontextofoverlaynetworksaredifferentfromthatintheconventionnetworksthatpresentsnewchallengesandnewproblemstosolve．Howtoimprovethemulticast-relatedperformanceofapplication-layermulticastisimportantforrealizationoflargescaleIntemetmulticastservices．Thisdissertationfocusesonho

6、wtoimprovetheperformancepenaltyofapplication·layermulticastbasedontwooverlaytopolo画es：treeandm—Dmesh，Ourobjectivesinthisdissertationaretheefficientintermsofshortmulticastdelay，scalableintermsofgroupsize，fullydistributedandqualityofserviceguaranteedapplication-layermulticastservices．Firstly，this

7、dissertationstudiedtheapplication—layermulticastprotocolbasedonthetreeoverlaytopology．Focusingtheimprovementofefficiencyandscalability，aFibooacciseriesbasedhierarchicalapplication—layermulticastprotocolisproposedinthecontextoftree