组播协议在OPNET中的建模与仿真

该文以IP组播技术为重点，结合网络仿真软件OPENT Modeler，分析该软件环境下IP组播网络的建模机制，包括参考标准、组的管理、支持的应用、组播路由协议的选择，节点加入组播组与发送源发送组播数据的流程。以校园网视频会议和FTP传输应用为例，构建网络仿真模型，一方面比较单播与组播方式下的网络性能，分析了视频流量的发送情况、视频会议分组的端到端延时，FTP传输的响应时间，骨干网络点到点链路吞吐量；另一方面比较了组播方式采用共享树机制和由共享树切换到最短路径树在网络性能上的改进，包括分组延迟的降低、汇合点路由器上拥塞发生的减少等。同时，也对无线移动通信网络环境下的组播技术提出更多需要考虑的因素。

Multicast Protocol Modeling and Simulation in OPNET

This article puts emphasis on IP multicast, using network simulation tool OPNET Modeler, to analyse the modeling mechanism for IP multicast network, including recommend standards, group management, supported applications, multicast routing protocol, processes of joining a multicast group and sending traffic to a group. A video conference and FTP data transmission in the campus network is chosen as an instance, simulation network model is built up. Results of performance tests with unicast and multicast are compared.We analyze video conferencing traffic sent, packet end to end delay, FTP upload response time and point to point link throughput of backbone network. What's more, the improvements of network performance by switching RP tree to Short Path Tree in multicast simulation are explained, such as reducing of packet end to end delay and congestion on the RP router. At the same time, some factors which should be taken into account in multicast under wireless and mobile communication networks are put forward.