The secure communication created using the PPTP protocol typically involves three processes, each of which requires successful completion of the previous process. This document explains these three processes and how they work:
PPP Connection and Communication. A PPTP client uses PPP to connect to an ISP by using a standard telephone line or ISDN line. This connection uses the PPP protocol to establish the connection and encrypt data packets.
PPTP Control Connection. Using the connection to the Internet established by the PPP protocol, the PPTP protocol creates a control connection from the PPTP client to a PPTP server on the Internet. This connection uses TCP to establish the connection and is a called a PPTP tunnel.
PPTP Data Tunneling. Finally, the PPTP protocol creates IP datagrams containing encrypted PPP packets which are then sent through the PPTP tunnel to the PPTP server. The PPTP server disassembles the IP datagrams and decrypts the PPP packets, and then routes the decrypted packets to the private network..