实现组播模式下连续数据流的可靠传输

IMPLEMENTATION OF RELIABLE MULTICAST TRANSPORT OF CONTINUOUS DATA STREAM

非实时大批量数据的组播传输是当前国际上重点研究的重要网络研究课题．文中针对点对多点通信模式下实现连续数据流可靠组播的问题，对目前存在的组播传输协议在实现可靠组播方面的优缺点进行了分析，在ＲＭＴＰ协议（一种可靠组播协议）的基础上，将需要传输的连续数据流划分为数据块（每个数据块由一定数量的数据包组成），并以数据块为单位通过ＲＭＴＰ协议进行可靠的组播传输，从而实现整个数据流的可靠组播传输．在构造组播树的过程中，按层次将组播组分为多个局部组，并在每个组中指定特定的接收者分级地承担本组内确认包的处理，从而将发送者从沉重的确认包处理中解脱出来，提高了系统的性能．文中分析了ＲＭＴＰ协议的理论性能，实现了该协议并在实际环境中测试和统计了吞吐量，同时也研究了理论值和试验数据之间的差异，解释了造成此种差异的原因．

The multicast transport of non-realtime bulk data is currently a hot research project in the field of network. In order to solve the problem of implementing the reliable transportation of continuous data stream, virtues and shortcomings of various existing reliable multicast protocols are analyzed in the present paper. Then, based on RMTP, an implementation scheme divides continuous data stream into data blocks, each block consisting of several packets, Through reliable multicasting each block, the whole data stream can be reliably multicast. It also adopts negative confirming to reduce the burden of sender. Also analyzed is the theoretic performance of RMTP. This protocol is implemented and the performance is tested and calculated in real environment. Finally, the reason of producing the difference between the result of test and that of the theoretic performance is studied.