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In recent years, with the rapid development of Internet and the popularity of the Internet has produced many new applications, such as network video conferencing, video broadcast, multimedia, distance education, tele-consultation, etc., which makes the rapid consumption of the bandwidth, network congestion brought problem. In order to alleviate network bottlenecks have been proposed and application layer multicast IP multicast technology, IP multicast routers to construct the multicast forwarding tree, when the data packets from the root of the tree that the data source is issued, the data packet forwarding along tree at different nodes distributed on the router, and finally reach each receiving terminal. Application Layer Multicast multicast function will transfer from the router to the end system, to complete all by the end system multicast group communication features, easier to deploy, can support a large number of groups, scalability, and can be a good solution to the multicast group address inadequate allocation problems, to carry out a wide range of multicast and application opens up new avenues. In this paper, the existing application layer multicast conducted in-depth research, the main research content and innovative work is divided into the following aspects: (1) in-depth study of existing application layer multicast protocols, the current application layer multicast protocol implementations preferred method is divided into a mesh topology, tree topology preferred method and implicit method three categories. For live streaming systems-oriented application background, focusing on analysis method based on implicit application layer multicast - University of Maryland's NICE. University of Maryland NICE protocol is a scalable application layer multicast protocols, mainly for a large number of recipients of low-bandwidth, data streaming applications, NICE in scalability, low latency and robustness, etc. can meet the large-scale streaming media transmission. (2) For the NICE network heterogeneity problem has been improved, the main method is proposed bandwidth constraints model, for improved protocol for a detailed design and analysis. (3) application of NS-2 对 The improved protocol simulation, simulation experiment was divided into two aspects, one simulation to examine improved protocol multicast tree relative delay consideration of two simulation comparison is improved protocol and NICE maximum delay, average delay and degree of stretching ratio of the two simulation results show that as the population continues to expand, the superiority of the improved protocol is more obvious. (4) designed and implemented based on application layer multicast streaming system, the system including the streaming media server, the multicast data sources, gathering point, the client four parts. And each of the major functional modules are implemented on the client side, the main achievement of the client user management module, multicast management module, streaming data processing module, forwarding and receiving streaming media data transmission module, the control packet transmission. The system is able to provide large-scale real-time multimedia data transmission services. The system and its various functional modules were tested and evaluated, the main contents of the tests, including the creation of a multicast group, the multicast group join and exit as well as the processing node failure, the test results show that the system basically meet the design requirements.
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