The Design And Implementation Of Firewall Module In MoIP Gateway

With the rapid development of Internet technology, the contradiction between requirement and implementation of information sharing has been effectively resolved, but the security of the opening information resource is becoming increasingly a problem of society and technology. As a safety barrier between local network and external network, firewall is an efficient model which can isolate the connection from unsafe network but not interfere with the access. Linux is an open source operating system and has good network performance; furthermore, the firewall subsystem Netfilter/iptables in Linux kernel 2.4/2.6 is concise, having high efficiency and good extensibility, which is chosen as the base of a firewall by many developers. It has good reference meaning and practical value using Linux Netfilter/iptables to implement the firewall in residential gateway.This thesis analyzes the implementation mechanism of Linux Netfilter/iptables after introduced the problem of network security and discussed the development of firewall technology. Based on requirement of residential gateway, the author designs the firewall module and depicts the course of realization in detail. The firewall includes a basic firewall and an extended one. The basic firewall has fixed rules according to the network application of gateway, while the extended firewall enhances the filtration functions of netfilter, and combines with web technique to let users custom the firewall rules, control the action time and check logs. Finally, the author designs test scheme to validate firewall's capability, the result on different test topology present this solution of firewall matches the requirement of residential gateway quite well.This method of building firewall has been adopted in residential gateway. The result and practice prove it a portable solution and applicable in various situations.