多源交互式应用层组播路由协议

摘要

Application layer multicast (ALM) without expanding the basic underlying network can support greater range of multicast communications, which makes it a popular mechanism for multicast applications.However, compared with the traditional IP multicast, ALM has larger network delay and the node stability is poor, which makes it become a unique and challenging problem to implement multi-source interactive multicast application.In this paper, an ALM protocol called Thunder is proposed.According to the roles of members in the group, Thunder divides the interactive group into core-network and peripheral-tree.The core-network consists of the multicast data sources.By using Mesh-Tree structure, it constructs an optimal distribution tree for each data source and pursues fast forwarding to optimize the interactive process.The peripherals-tree is a tree structure composed by the unstable members which just receive data or only produce a small amount of data.Additionally,Peripherals-tree structure allows more members to receive multicast data.Those unstable nodes will not influence the interaction process of core-network, so the response speed and the protocol scalability of the interactive process are improved.Experiments demonstrate that Thunder can decrease network delay of interactive ALM and improve the scalability, which makes the multi-source interactive multicast applications be deployed and implemented more easily.%应用层组播无需扩充底层基础网络就可以实现较大范围的组播通信,已成为倍受瞩目的组播实现机制.但相对于传统的IP组播,应用层组播的网络延迟大,节点稳定性差,使得采用应用层组播来实现多源交互式组播应用成为一个独特的具有挑战性的问题.Thunder协议将组播结构分为核心网和外围树两部分:核心网通过Mesh-Tree结构追求快速转发以优化交互式过程;外围树允许更多的成员接收组播数据,却不会对交互过程产生影响,可提高协议的扩展性.实验表明,Thunder协议能够减小交互式应用层组播的网络延迟,具有较好的扩展性和容忍延迟变化特性,适用于各种不同规模网络.