A very basic VPN protocol based on PPP. PPTP was the first VPN protocol supported on the Microsoft Windows platform. The PPTP specification does not actually describe encryption or authentication features and relies on the PPP protocol being tunneled to implement security functionality.
An advanced protocol formally standardized in IETF RFC 3193 and now the recommended replacement for PPTP where secure data encryption is required.
OpenVPN is an advanced open source VPN solution backed by the company ‘OpenVPN technologies’ and which is now the de-facto standard in the open source networking space. It uses uses the mature SSL/TLS encryption protocols.