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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,P2P,流媒体系统的若干关键属性的优化方案,指导教师：陈贵海 教授,1,提纲,2,P2P,流媒体系统,P2P,研究的重要子领域,典型系统,Skype,UUCall,PPLive,PPStream,新浪,UUSee,激烈竞争,3,研究意义,2008,年,1,月,17,日中国互联网发展状况统计报告,中国内地网民观看网络视频的几种主要方式中，通过,P2P,流媒体下载软件的比率达到,29.91%,，接近三分之一！,学术界,SIGCOMM07,：微软研究院（华人,1,、,2,作）,SIGCOMM08,：,PPLive,公司,+,香港中文大学（华人,all,）,Rank1,：,INFOCOM,、,ICNP,、,ICDCS,、,Rank2,：,IPDPS,、,ICPP,、,NOSSDAV,、,4,概念,功能分类：,实时播放（,Live Streaming,）,点播（,VoD,，,Video on Demand,）,工作方式分类：,树状多播,网状多播（基于,Gossip,协议）,5,比较,网状多播已成为,P2P,流媒体的主流,6,P2P,流媒体系统的属性,7,关键属性,选取依据,1,、直接影响用户体验，,2,、或对系统性能至关重要，,3,、可优化空间大，,4,、优化涉及到的人为因素少,关键属性,播放连续度,、启动时延、,源切换时延,、,系统容错性,、可扩展性。,8,本文的工作,9,优化方案,1,：具有高播放连续度的,P2P,流媒体系统的设计,10,背景与动机,Gossip,多播的固有缺陷：,随机性、不确定性,前人工作多从优化数据调度算法着手,光优化数据调度算法是不够的！,11,我们的工作,12,ContinuStreaming,系统架构,13,数据预取：紧迫界限机制,动态预测,自适应调整,14,性能评价,播放连续度从,80%,左右提升到,95%,左右（左图），额外开销低于,4%,（右图）。,15,优化方案,2,：流媒体发布源的快速切换,16,背景,多个媒体发布源，串行工作,17,动机,同样的带宽，不同的源切换算法，源切换时间不同,18,我们的工作,19,过程建模,优化目标：最小化,T,2,20,快速源切换算法,优化目标：最小化,T,2,21,快速源切换算法,相比传统源切换算法，源切换时间减少,20-30%,，额外开销没有增加,22,优化方案,3,：底层覆盖网的拓扑优化,23,背景与动机,底层覆盖网对,P2P,流媒体系统的至关重要性：只要覆盖网分割，流媒体系统就陷于中断,底层覆盖网拓扑关键点的存在：割点,分点,C,7,6,5,C,1,2,3,4,D,TTL,TTL,C,C,1,2,3,4,5,6,7,24,我们的工作,25,分点定义,定位,可达,分点,TTL,3,2,1,4,TTL,TTL,TTL,3,2,1,4,C,7,6,5,C,2,3,4,1,26,分点检测,6,7,C,C,1,5,2,3,4,Msg_Response,Msg_Init,6,7,C,C,1,5,2,3,4,Msg_Probe,7,5,3,1,6,7,C,C,1,5,2,3,4,1,7,5,3,1,Msg_Probe,6,7,C,C,1,5,2,3,4,Msg_Arrival,5,7,1,3,6,7,C,C,1,5,2,3,4,Yes!,7,C,C,1,5,3,（,0,）网络初始状态 （,1,）启动检测 （,2a,）探测可达性,I,（,2b,）探测可达性,II,（,3,）收集可达关系,（,4,）划分子集、判定分点,27,性能评价,28,总结,(1),Book:,Guihai Chen,and,Zhenhua Li.,Peer-to-Peer Network: Structure, Application and Design (,对等网络：结构、应用与设计,). Tsinghua University Press, Sep. 2007. About 400K characters in Chinese.,Journal Paper:,Huan Chen, Guihai Chen, Zhenhua Li and Xiaomei Cao. A Market Model based Reputation management Mechanism for Peer-to-Peer Networks. Accepted by,Journal of Chinese Computer Systems,(,小型微型计算机系统,) 2008, in Chinese with English abstract.,Ruifeng Yuan, Zhenhua Li and Guihai Chen. Enhancing Overlays Performance with Virtual Node Switch Mechanism. Accepted by,Computer Science,(,计算机科学,) 2008, in Chinese with English abstract.,Zhenhua Li, Guihai Chen and Tongqing Qiu. Partition Node: the Topologically Critical Nodes of Unstructured P2P Network. Accepted by,Chinese Journal of Software,(,软件学报,) 2007, in Chinese with English abstract.,29,总结,(2),Conference Paper:,Zhenhua Li, Jiannong Cao, Guihai Chen and Yan Liu. Fast Source Switching for Gossip-based Peer-to-Peer Streaming. The 37th International Conference on Parallel Processing,(ICPP 2008),September 8-12, 2008 in Portland Oregon, USA.,Zhenhua Li, Jiannong Cao and Guihai Chen. ContinuStreaming: Achieving High Playback Continuity of Gossip-based Peer-to-Peer Streaming. The 22nd IEEE International Parallel and Distributed Processing Symposium,(IPDPS 2008),April 14-18, 2008 in Miami Florida, USA.,Zhenhua Li,and Guihai Chen. Detecting and Reducing Partition Nodes in Limited-routing-hop Overlay Networks. The 6th International Conference on Grid and Cooperative Computing,(GCC 2007),pages 19-25, August 16-18, 2007 in Urumchi, Xinjiang, China.,Junfeng Xie,Zhenhua Li,and Guihai Chen. A Semantic Overlay Network for Unstructured Peer-to-Peer Protocols. The 13th International Conference on Parallel and Distributed Systems,(ICPADS 2007),pages 1-8, December 5-7, 2007 in Hsinchu, Taiwan.,Zhiyu Liu, Ruifeng Yuan,Zhenhua Li, Hongxing Li and Guihai Chen. Survive under High Churn in Structured P2P Systems: Evaluation and Strategy.,Lecture Notes in Computer Science (Proceedings of,ICCS 2006,),Volume 3994, pages 404-411, May 28-31, 2006 in Reading, UK.,30,展望,展望,1,、实时系统的研究趋于成熟，,P2P,点播系统的研究非常有价值：,SIGCOMM07/08,的两篇论文都是关于,P2P,点播系统,2,、,P2P,流媒体系统的多个属性间关系的研究,3,、,P2P,流媒体领域的研究空间仍然很大，并非某些学者认为的“大势已去”、“穷途末路”。,31,谢谢！,感谢各位参与答辩的老师和同学！,32,
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