一种实时可靠多播协议延迟性能分析

现有的可靠多播协议种类繁多,但尚不能满足有些应用中的特殊实时性要求,即在新数据不断以固定时间步长到达之前,必须完成旧就数据的修复,否则旧数据将会失效.实时可靠多播协议正是针对这种特殊需求提出的,该协议采用了混合FEC、分层网络局部修复技术和一种主动NAK机制,可有效控制并降低修复时间,同时还采取了NAK抑制机制使协议具有较好的扩展性能.为了评价协议的性能,论文在建立协议传输模型的基础上,基于泊松理论,精确地量化了节点和端系统的处理延迟以及修复过程延迟,导出了其传输延迟的计算公式.仿真计算结果表明,该实时可靠多播协议的传输延迟性能稳健,且表现出较好的可扩展性,能够满足应用的要求.

Analysis of Delay Characteristic in a Real Time Reliable Multicast Protocol

There have been various reliable multicast protocols now,but they can't satisfy special real-time requirement in applications,that is,before new data reach continuously in a certain time step the old data must be recovered,otherwise,the old data are invalidated.A real time reliable multicast protocol is put forward for the special application requirement.It takes techniques of hybrid FEC,hierarchical network local recovery and an active NAK mechanism to control and reduce the recovery time effectively,and use NAK suppression mechanism to preserve its high scalability.For evaluating the performance of the protocol,the processing and recovery procedure delays in the node and end-system are quantitated accurately through the Passion theory on the basis of modeling the protocol communication in this paper.Then the transport delay calculating formula is presented.The simulated results show the transport delay of the protocol has good robustness and scalability.