Secure Socket Tunneling Protocol (SSTP) is a form of VPN tunnel that provides a mechanism to transport PPP or L2TP traffic through an SSL 3.0 channel
SSTP is only available in Windows since version Windows Vista SP1, in RouterOS, and in SEIL since its firmware version 3.50. It is fully integrated with the RRAS architecture in these operating systems, allowing its use with Winlogon or smart card authentication, remote access policies and the Windows VPN client.