The PPTP GRE packet format is non standard, including a new acknowledgement number field replacing the typical routing field in the GRE header. This TCP connection is then used to initiate and manage a GRE tunnel to the same peer. PPTP has not been proposed nor ratified as a standard by the Internet Engineering Task Force.Ī PPTP tunnel is instantiated by communication to the peer on TCP port 1723. The intended use of this protocol is to provide security levels and remote access levels comparable with typical VPN products.Ī 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 Nokia), 3Com, and others. The PPTP implementation that ships with the Microsoft Windows product families implements various levels of authentication and encryption natively as standard features of the Windows PPTP stack. The PPTP specification does not describe encryption or authentication features and relies on the Point-to-Point Protocol being tunneled to implement any and all security functionalities.
Many modern VPNs use various forms of UDP for this same functionality. PPTP uses a TCP control channel and a Generic Routing Encapsulation tunnel to encapsulate PPP packets. PPTP has many well known security issues.
The Point-to-Point Tunneling Protocol ( PPTP) is an obsolete method for implementing virtual private networks.
