截包的需求一般来自于过滤、转换协议、截取报文分析等。 过滤型的应用比较多，典型为包过滤型防火墙。 转换协议的应用局限于一些特定环境。比如第三方开发网络协议软件源码，不能够与原有操作系统软件源码融合，只只好采取““嵌入协议栈的块”（BITS）方式实施。比如IPSEC在Windows上的第三方实现，无法与操作系统厂商提供的IP软件源码融合，只好实现在IP层与链路层之间，作为协议栈的一层来实现。第三方PP

-Cut package the needs of the general from the filter, the conversion agreement, the interception of packet analysis. The application of the filter type is more typical for packet filtering firewall. Convert the application of the agreement is limited to the specific environment. Development of network protocols such as third-party software source code, can not be integration with the original operating system software source code, only had to take the " embedded protocol stack"　(BITS) manner, such as IPSEC third-party implementations on Windows, you can not with the operating IP software source system vendors to provide integration, but to achieve between the IP layer and link layer protocol stack layer to achieve third-party PP