Because of the one-to-one structure of the Internet was broken by the proxy server and NAT gateway applications in the Internet, the structure of inner network behind the proxy server and NAT gateway is unknown to the public network namely external network. 由于代理服务器以及NAT网关的应用打破了互联网络一对一的结构模式,公网即外部网络对于代理服务器及NAT网关后的内网结构是未知的。