(First of all, let us focus on one point. The PPP we are talking about here is not to configure our server as a server that provides dial-in services, but users can dial-up Internet access through the server. In short, the server can automatically according to customer needs. Dial-up Internet access, also known as dial-on-demand. Why are we introducing this configuration to us? Because although many enterprises now use DDN to surf the Internet, Modem)