| 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.
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