Abstract: Application Layer Multicast（ALM） has resolved the issue of deployment，but effectiveness inferiors to IP multicast.To build a high efficient multicast tree，the research is focused upon the influence on the communication efficiency of the multicast tree using three kinds of node selection strategy，which are based on Min-delay，Max-bandwidth，and Nearest network topology.The degree of nodes is limited to build the multicast tree at different network scale.Simulation experiments show that the strategy based on Min-delay is the lowest in average delay and average joining time，and is much more suitable for the delay-sensitive application.

Key words: computer network, Application Level Multicast（ALM）, multicast trees

摘要： 应用层组播解决了网络层组播难于部署的问题，但是效率不及网络层组播。针对如何构建一棵高效的应用层组播转发树的问题，重点研究了基于最小路径延迟、基于最大链路带宽、基于最近网络拓扑三种父母节点选择策略对转发树通信效率的影响。仿真实验结果证明，在约束节点度前提下，不同的网络规模中，基于最小路径延迟方法生成树的平均延迟、平均加入时间最小，更适合于延迟敏感型的应用。

关键词: 计算机网络, 应用层组播, 组播树