中文摘要：

应用层组播采用终端主机转发数据的方式，在一对多的媒体内容分发方面具有广阔的应用前景．与IP组播相比，应用层组播具有灵活和易实施的特点，但是因为终端主机可以自由地退出组播树，应用层组播也存在数据传递易中断的缺点，这对实时性要求严格的视频直播应用的影响尤为严重．通过对超过1000万条实际视频直播系统的真实用户记录进行统计分析，发现用户平均剩余在线时间随着已经在线时间的增大而增大，并据此提出了一种适用于视频直播的应用层组播树生成算法．模拟结果表明，算法对减少视频直播应用下应用层组播树的数据传递中断次数有明显作用．

英文摘要：

Application layer multicast （ALM） which uses end hosts to relay data has a prosperous prospect in one-to-many media content distribution. Compared with IP multicast, ALM is more flexible and deployable. But data delivery in ALM tree can be easily interrupted by departure of end hosts, which may lead to degradation of QoS in time-sensitive applications such as live streaming. Proposed in this paper is a new ALM tree construction algorithm based on the analysis of over 10,000,000 real log traces from a popular live streaming system in China. The algorithm can significantly reduce the interruption times of ALM tree in live streaming and its effectivity has been verified through simulation.