Access Control And Domain Filtering Techniques In The National Tax System

The main purpose of Access Control, a major technique of network security prevention and protection, is to safeguard network resources from being illegally visited and used. The Access Control is one of the core strategies of the network security, as well as a major component of information safety technology. The major function of a domain name system is to resolve the URL address, which has been developed for more than 20 years, and is still developing and exploring new functions.The network of the National Taxes System is a typical Intranet structure. Networks at different levels are connected with routers. Within each level of network, there are some severs and work stations, and provide the services of domain name resolving and other office applications. The large structure, multiple levels, rapid development, huge number of computers, as well as the Windows operation system installed in most of computers, cause some problems gradually, with the continuous development of network construction. One of the prominent problems is the junk flow caused by the access to invalid or illegal domain name in the network system. These accesses always result in the network jam, which decreases the efficiency of network application, and even worse, constrains normal work.Based on the access control and domain system and integrated with problems in the development of National Taxes Network system, this article studies and analyzes the functional characteristics of Package Filter and Domain Name Filter techniques in detail, and applies the combination of these two techniques to proposes a comprehensive plan in practice. On one hand, access control function based on package filter was achieved in CISCO and Bay routers. On the other hand, domain name filter function based on conditional forwarding was accomplished in the DNS servers applied Windows and Unix operation systems. In addition, a hole in the Microsoft DNS server setup was found from application researches. A solution was suggested after analyses and tests. The application of this comprehensive plan at various levels of network effectively decreased the junk flow related to the domain name searches, and improved the usage and work efficiency of the network.This article makes a further research on the base of conditional forwarding, puts forward a concept of domain name filter, shows us a reconstructive resolving process of domain name, programming of filter function, and the result of elementary research. That makes a good basement for expanding and perfecting DNS service on the function of domain name filtering.