SSTP VPN protocols work similarly to PPTP as they secure and transfer PPP traffic. However, SSTP VPNs utilize an SSL/TLS channel which the PPTP doesn’t. Hence, SSTP VPN protocols offer more security than PPTP. They are also unique because they offer secure key negotiation, encryption, and traffic integrity checking. SSTP is not the most popular VPN protocol because it works best for Windows users only. While it is possible to use on Android and Linux devices, it is difficult to set up properly. Services that offer the SSTP protocol usually cost between $3 to $10 depending on the length of the subscription period.