The (PPTP) Point-to-Point Tunneling Protocol is an obsolete method for implementing virtual private networks, with many known security issues. PPTP uses a control channel over TCP and a GRE tunnel operating to encapsulate PPP packets.
The PPTP specification does not describe encryption or authentication features and relies on the Point-to-Point Protocol being tunneled to implement security functionality. The most common PPTP implementation shipping with the Microsoft Windows product families implements various levels of authentication and encryption natively as standard features of the Windows PPTP stack. The intended use of this protocol is to provide security levels and remote access levels comparable with typical VPN products. A specification for PPTP was published in July 1999 as RFC 2637 and was developed by a vendor consortium formed by Microsoft, Ascend Communications (today part of Alcatel-Lucent), 3Com. PPTP has not been proposed nor ratified as a standard by the Internet Engineering Task Force.