A tutorial on setting up VPN server based on PPTP under CentOS

PPTP, that is, the PPTF protocol. This protocol is a new enhanced security protocol developed on the basis of PPP protocol, which supports multi-protocol virtual private network (VPN), and can enhance security through the methods of Password Authentication Protocol (PAP), Extensible Authentication Protocol (EAP), etc. You can enable remote users to securely access the enterprise network by dialing into the ISP, by connecting directly to the Internet, or through other networks.

PPTP: Point-to-Point Tunneling Protocol

(Pptp:point to Point tunneling Protocol)

Point-to-Point Tunneling Protocol (PPTP) is a network technology that supports multi-protocol virtual private networks, and it works on the second tier. With this protocol, remote users are able to access the corporate network securely through Microsoft Windows NT workstations, Windows XP, Windows 2000 and Windows2003, the Windows7 operating system, and other point-to-point protocol-equipped systems. and can dial in to the local ISP and link to the corporate network via Internet security. It Chen Yi

The PPTP protocol assumes a connected and available IP network between the PPTP client and the PPTP server. Therefore, if the PPTP client set Step 1 is already part of the IP network, it can be connected to the PPTP server through that IP network, and if the PPTP client is not already connected to the network, such as in the case of Internet dial-up users, The PPTP client must first dial the NAS to establish an IP connection. The PPTP client referred to here is the VPN client that uses the PPTP protocol, and the PPTP server is the VPN server that uses the PPTP protocol.

PPTP can only be implemented through PAC and PNS, and other systems do not need to know PPTP. Dial-up networking can be connected to the PAC without having to know PPTP. The standard PPP client software continues to operate on the tunnel PPP link.

PPTP uses an extended version of the GRE to transmit user PPP packages. These enhancements allow low-level congestion control and flow control for tunnels that transmit user data between PAC and PNS. This mechanism allows efficient use of tunnel available bandwidth and avoids unnecessary postbacks and buffer overflows. PPTP does not specify that a particular algorithm is used for low-level control, but it does define some communication parameters to support such arithmetic work.