随着信息技术的发展，网络结构和规模越来越复杂，使得网络的规划和设计、网络设备的研发以及网络协议的开发变得越加困难，因而急需一种科学的手段来反映和预测网络的性能，网络仿真技术应运而生。借助仿真技术，可以非常有效地提高网络规划和设计的可靠性和准确性，明显地降低网络投资风险，减少不必要的投资浪费，因此网络仿真已经成为数据网络领域的热点问题。 本论文主要是借助OPNET其强大的网络建模功能对数据包传输网络的建模方法进行研究并给出了实现过程。本文首先介绍了OPNET网络仿真软件及仿真步骤，探讨了OPNET的工作机制、通信机制、仿真系统的核心技术。接着在OPNET网络仿真的理论基础上，深入地讨论了仿真建模技术，描述了使用OPNET进行网络仿真研究的工作流程。本文在基于OPNET网络仿真软件提供的开发环境基础上，建立了一个中心节点和八个外围节点的数据包网络，其网络性能可以由链路利用率及经过网络的通信量产生的端到端延迟来判断。模型的八个外围节点产生信息流，这些信息流由中心节点传送到网络相应目的地，通过使用仿真编辑器对不同的数据包到达时间间隔创建五个不同仿真来研究数据包生成速率对于网络性能的影响。最后在所建立的仿真网络的基础上，增加第二个子网络，在相同的数据包发送间隔时间的前提下，选择在同一条链路上的相同两个节点仿真得到网络的链路利用率与同一个子网的端到端延迟，并与网络扩展前的端到端延迟的结果来进行对比，仿真结果表明网络扩展计划可以实施。

Withing the development of information technology, the network structures and scales are becoming complicated. It is difficult to program and design the network, the development of the network protocols, and the design of the network equipments also. So there has an urgent need of means in science urgently to reflect and predict the function of the network, the system simulation technique emerges with the tide of the times. The application of system simulation techniques can raise the credibility and accuracy of the network programming and designs; furthermore it can lower the network investment risk clearly, and reduce the investment waste. The network simulation becomes hot issues of the data network domain. The paper focuses on research the solution of establishing the model of packet transmitted network and implement of it , withing the powerful simulation of network modeling of OPNET. First, the paper introduces a new network simulation software ——OPNET, it has powerful function in network modeling and simulation, discuss its simulation steps, work system、communication system、the core technology of simulation system, on the theory base of OPNET, discuss the simulation modeling technology, the working program of OPNET in network simulation is studied. Based on the development environment for the simulation of network which the OPNET software provides, the goal is to set up a packet network, which has one hub node and eight peripheral nodes. In a simple packet transmitted network, the performance of the network can be measured by the link utilization and the end-to-end delay experienced by traffic on the network. The eight peripheral nodes of model generate traffic while a central hub node relays the traffic to the appropriate destination within the network. To see the effect of the packet generation rate on the performance of the network, using the Simulation Editor to create five simulation sets for different packet interarrival time. In this last part of the lesson, it interested in discovering how adding a second network affects the link utilization of the same link and the end-to-end delays of the same subnet, comparing with the foregoing result, it indicates the plan of expanding the network can bring into effect.