防火墙是一种重要的网络安全技术 .对防火墙的核心技术——规则和推理机进行了研究 ,提出了增强型包过滤防火墙的规则形式化定义、推理机的抽象模型和推理算法 .据此 ,设计和实现了相应的推理机 ,同时给出了防火墙的设计实例 ,以此做为对上述工作的验证 .最后 ,总结了该防火墙的优点 ,并指出了进一步的研究目标 Firewall is an important network security technology.Study on the core technology of firewall - rule and reasoning engine, put forward the formal definition of rules, the abstract model of reasoning engine and reasoning algorithm of enhanced packet filtering firewall.Accordingly, Designed and implemented the corresponding reasoning machine, at the same time gives the design examples of the firewall, in order to verify the above work.Finally, summarizes the advantages of the firewall and points out the further research goals