(Point-to-Point Tunneling Protocol) A protocol from Microsoft that is used to create a virtual private network (VPN) over the Internet. Remote users can access their corporate networks via any ISP that supports PPTP on its servers.

PPTP encapsulates any type of network protocol (IP, IPX, etc.) and transports it over IP. Thus if IP is the original protocol, IP packets ride as encrypted messages inside PPTP packets running over IP. PPTP is based on the point-to-point protocol (PPP) protocol and the generic routing encapsulation (GRE) protocol. Encryption is performed by Microsoft's Point-to-Point Encryption (MPPE), which is based on RC4. See L2TP.