Design And Implementation Of A Network Simulation System With Dynamic Routing

In recent years, with the continuous development of Internet technology and informatization, people’s life has been greatly improved, but the Internet technology has also brought us a lot of problems. On one hand, various kinds of network security problems continue to emerge, and information security incidents also happen now and then. On the other hand, the increased complexity and scale of network demand more on the existing protocols and algorithms, so researchers are supposed to do some prospective studies. Due to the advantages of low cost, high flexibility and large scale, network simulation has been widely used in the research of network behavior and network protocols.In the real network environment the quality of routing strategies can affect the performance of a network directly, and in the same way, how to simulate the process of packets forwarding in the real network environment will affect the authenticity and efficiency of the simulation directly. Therefore, it is of great importance to design a good routing strategy.Based on the above background, this article designed and achieved a network simulation system supporting dynamic routing based on the open source network simulation tool NS3. The main research contents are as follows:Firstly, this paper studies the dynamic routing protocols widely used in the current network, analyzes the advantages and disadvantages of each protocol, and then achieves the OSPF protocol on NS3, which mainly includes:obtaining of the link state advertisements, construction of the link state database, implementation of the shortest path first algorithm in the routing selection protocol, generation of the routing table, and realization of routing update process.Secondly, due to the increase of network information, network congestion has become the main factor restricting the performance of network. The widely used routing protocols such as OSPF, RIP and IGRP always choose the optimal routing when the packets being forwarded, so other free links will not be utilized while the optimal link is congested, which leads to the waste of a large amount of network resources. In order to control network congestion, this paper proposes a congestion perception queue model. In this model a periodic testing of queue buffer occupancy rate is performed to predict whether the link is going to be congested or not and when the queue buffer occupancy rate reaches a certain threshold, the link is considered more likely to be congested.Thirdly, to deal with the congestion problem mentioned above, this paper presents a congestion perception routing algorithm (CPRA). A local routing strategy is adopted in this algorithm, whose main idea is:when the queue buffer occupancy rate reaches a certain threshold, a Breadth First Search algorithm is performed to find an alternate path to the destination node, and then the packets will be forwarded along the alternate path when congestion occurs. Extensive simulation results on NS3show that, compared with OSPF, CPRA can greatly improve the network performance, which includes raising the network throughput by about50%and decreasing the average end-to-end delay by about0.3s.