Design And Implementation Of An ARM9-Based Network Access Control Gateway

With the rapid development of Internet technology and the popularization of network application, Internet has more and more important influence on people's living and work, whereas problems caused by network occur. Online chatting of employees results in low efficiency, and the secret information of enterprise may be spread via Internet, which will cause severe economic losses. At the same time, adolescent are addicted to on-line chatting and playing games, even accessing undesirable site, which do serious harm to them. In order to improve work efficiency, ensure the safety of enterprise secrets and adolescents'healthy development, network users hope to establish an access control system which will promote the standardized, institutionalized and procedured working environment. Therefore, an ARM9-Based Network Access Control Gateway is designed and. implemented.The system is based on ARM9 processor, connected with some kinds of memories. To satisfy various kinds of application requirements, it also integrates many network interfaces. And debugging can be done through JTAG interface, exchanging information between users and system can be implemented by RS232 interface, and system upgrading and maintenance can be implemented by loading program image through network interface. Linux operating system is embedded in the system. To control the network access of client PC in LAN, the network access control system is designed based on Netfilter/Iptables which is the framework of Linux firewall, and it is implemented by Iptables. The Network Access Control system interacts with users in the form of Web pages. Apache server and CGI technique are applied to design the access control Web pages, and the function of NAT, Route Configuration, IP restriction, and network access control are implemented.Background and practical significance of the system are introduced at the beginning of this thesis. Comparing different embedded microprocessor, different embedded operating system, and according to practical demands, the whole design solution of the system is given. Furthermore, the design and implementation of hardware and software are introduced. The whole structure of hardware is given, and the detail circuits of each hardware module are introduced. Then the function, design and relevant problems of Bootloader are stuyed and discussed. And, the specific porting process of. Linux kernel in the hardware is described. After a brief description about the working process of software part, detailed discussions on each function module are given. Finally, the testing methods are given, and according to the testing result, the system could fulfill the demand.