This article describes how to utilize the VPN to construct the new Extranet’s topology. Firstly, it tells what is the Extranet. Secondly, some basic principles and technical idioms of the VPN are dealt with. Thirdly, tunnel protocols about VPN are discussed. Finally, three kinds of Extranet’s architectures with VPNs are given. Through integrating the VPNs into the Extranet, we can get much more benefits from shared networks (e.g., Internet, ISDN, PSDN, etc.).
