Design And Implementation Of A Packet Under The Unix System Dynamic Forwarding Gateway

Internet in China is primarily consisted of four networks at present: ChinaNET, CERNET, ChinaGBN and CSTNET. There is relatively high transmission time delay across such different networks, making it one of the main bottlenecks in the development of the domestic information high way.CERNET users are always affected by the communication bottleneck between CERNET and ChinaNET. Even if the users have access lines for the two networks at the same time, they also have to inconveniently switch the connection between the two networks by hand. The main purpose of this thesis is to realize a packet forwarding gateway server based on TCP/IP in the UNIX environment, which is able to help CERNET users access the Internet transparently. Different from traditional routers, the gateway proposed here focuses on the routing strategies rather than the routing protocol itself. It maximizes the utilization rate of each network access line by forwarding data packets according to the routing strategies of each network respectively.This thesis presents the design and implementation of a multi-functional dynamic packet forwarding gateway in the UNIX environment. The gateway is robust, efficient, secure, and completely transparent to its users. With the help of FreeBSD operating system, it is able to handle data packets faster and accept more users simultaneously. This thesis firstly introduces the bottleneck across networks, followed by the design of the dynamic packet forwarding gateway, as well as the analysis of the User Demand. The gateway software system is divided into four models, with each model's design and implementation discussed from Chapter 3 through 6 respectively. The functions and performances of the forwarding gateway are tested in chapter 7, where the testing data and results are generated. Chapter 8 is the conclusion of the whole thesis.