以前对防火墙接触甚少，所了解的也是从系统底层实现角度看的一些分析细节，最近由于毕业设计的需要，对防火墙的发展、分类、现状和趋向等方面做了概略的了解，也有一些体会，做个简单的分析报告。 -previously little contact with the firewall, as well as knowledge of the underlying system from the point of view of achieving the details of some analysts,