摘要： 由于配置困难以及控制技术的复杂性，IP 组播(IP Mmulticast，IPM)至今仍未在Internet 上得到推广。而以Overlay 方式在Internet中提供灵活有效的组播服务则成为近年来网络研究的一个热点。如何在基于Overlay 的Internet 组播(Overlay Multicast，OM)中实现有效的QoS 和可靠性保证，这已成为OM 研究的新课题。该文通过建立组播QoS 的数学模型，对基于Overlay 实现Internet 组播的QoS 和拥塞控制的机制进行了分析和探讨。

关键词: 组播QoS；拥塞控制；Overlay；Internet

Abstract: Due to complex implementation and difficult deployment, IP multicast has not been widely deployed on Internet till now. While up to now, overlay technology, by which multicast can be surported flexibly and effectively on Internet, has become a research focus. However, how to utilize overlay schemes to achieve efficient QoS and reliability guarantee for Internet multicast applications, it remains to be an open issue. This paper makes efforts to analyze the mechanisms of implementing QoS and congestion control in Internet multicast by overlay. All the analysis base on some math models of multicast QoS, and several meaningful results have been given: OM can effectively utilize various control functions implemtnted in upper layer, and provides more flexible and efficient QoS as well as reliability assurement than IPM in hop-by-hop fashion.

Key words: Multicast QoS; Congestion control; Overlay; Internet