2021
https://ru.vpnmentor.com/blog/%d1%81%d1%80%d0%b0%d0%b2%d0%bd%d0%b5%d0%bd%d0%b8%d0%b5-%d0%bf%d1%80%d0%be%d1%82%d0%be%d0%ba%d0%be%d0%bb%d0%be%d0%b2-vpn-pptp-vs-l2tp-vs-openvpn-vs-sstp-vs-ikev2/