DirectAccess IP-HTTPS Null Encryption and SSTP VPN
IP-HTTPS was always the slow pig of IPv6 network transition protocols. The reason for that was the multiple layers of encryption required for the connection. The good news is that newer versions of DirectAccess have removed one of the layers of encryption by use null encyrption for the HTTPS protocol.
Check out some of the details at http://directaccess.richardhicks.com/2014/06/24/directaccess-ip-https-null-encryption-and-sstp-vpn/