Which protocol is an open standard protocol framework that is commonly used in VPNs, to provide secure end-to-end communications?

“The PPTP specification does not describe encryption or authentication features and relies on the Point-to-Point Protocol being tunneled to implement security functionality. However, 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.”

….learned that years and years ago….forgot it because I’ve only SEEN PPTP used ONCE in the last 15+ years of IT work. It was running from a Windows 2003 server and the firewall had been set with basic PAT to allow ports through.