本书从介绍安全问题入手，讨论了TCP/IP协议簇的重要部分；随后，详尽描述了防火墙的结构，分析了几种常用防火墙网关，详细阐述了各种鉴别策略的选择及多种网关工具的使用，是管理工作人员必不可少的一本书。-This book from start to introduce security issues, discussed the TCP/IP protocol an important part of cluster　Subsequently, a detailed descr iption of the structure of a firewall, an analysis of several commonly used firewall gateways, elaborated on the strategy of identification and a variety of network choices Guan tools is essential for the management staff of a book.