【作者】 赵春芬；

【导师】 方旭明；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2003， 硕士

【摘要】 移动计算机的广泛应用推动了人们对移动计算机无线接入的研究，即对移动因特网的研究。移动IP是一种全球因特网上提供移动功能的网络层解决方案，它简单、可扩展，得到学术界的普遍认可。 移动IP中存在的一个重要问题就是三角路由，它带来了网络花费和性能问题。论文首先分析了两种移动IP路由优化技术——ROMIPv4和MIPv6，并通过仿真对其性能进行分析和比较。 移动IP中存在的另外一个问题就是：移动环境下TCP性能下降。论文通过仿真分析了移动IP切换造成TCP性能下降的原因，说明为了更好的满足用户需求，移动IP和TCP需要做进一步改进。 论文的第六章分三类阐述了现有的移动环境下TCP性能改进方案；之后提出了一种端到端的基于ROMIPv4的TCP改进方案一—TCP-BROMIPv4。这种方案利用ROMIPv4中的绑定更新消息以及新增的切换警告消息，调整发送TCP在移动节点切换过程中的操作。采用网络仿真工具NS2对TCP-BROMIPv4进行仿真，仿真结果表明：移动环境下TCP-BROMIPv4协议较传统的TCP协议在TCP性能上有了显著的改善。 移动环境下的TCP性能以及各种TCP改进方案在移动IP扩展协议下的性能还有待进一步研究，以便最终实现用户在网络间平滑切换，所进行的应用不中断，移动节点在网络切换过程中TCP性能对用户透明这一目的。更多还原

【Abstract】 Recent years there has seen an explosive growth in the number of laptop and notebook computers sold, which has driven the research in mobile host accessing Internet, i.e., mobile Internet. Mobile IP is thus a solution for mobility on the global Internet. It has gained universal acceptation in academia because of its simplicity and scalability.Triangle Routing is an important issue in Mobile IP, which also brings problems in network cost and performance. Firstly, this paper analyzes two of existing techniques of routing optimization in Mobile IP, which are ROMIPv4 and MIPv6. Subsequently, their performance is analyzed and compared with each other through simulation.Another issue in Mobile IP is that TCP performance in mobile environments is far from satisfied. In the following part, the thesis analyzes TCP performance in mobile environments. Some reasons causing negative effects on the TCP performance during Mobile IP handoff are described in detail. It concludes that both Mobile IP itself and TCP need to be improved in order to meet users’ requirements.Chapter 6 of the thesis analyzes three kinds of solutions for improving TCP performance in mobile environments and then presents an end-to-end solution for TCP performance improving, which is based on ROMIPv4. In this solution, sender TCP may adjust its operation when it receives Binding Update message and the Handoff Warning message newly ’ defined in ROMIPv4. The TCP-BROMIPv4 protocol is simulated using network simulator NS2.The simulation results show that TCP-BROMIPv4 has greatly improved TCP performance compared to the original TCP protocol in mobile environments.Both TCP performance in mobile network and the improving solutions’ co-operation with Mobil IP extensions are to be deeply researched in future. Our ideal is to realize that subscribers smoothly hand over in networks and that application ongoing isn’t interrupted. In the end TCP performance is transparent for users during mobile hosts handing over.更多还原