Explanation/Reference:
Note:
* DirectAccess, introduced in the Windows 7 and Windows Server 2008 R2 operating systems, allows remote users to securely access enterprise shares, web sites, and applications without connecting to a virtual private network (VPN).
DirectAccess establishes bi-directional connectivity with a user's enterprise network every time a user's DirectAccessenabled portable computer connects to the Internet, even before the user logs on. Users never have to think about connecting to the enterprise network and IT administrators can manage remote computers outside the office, even when the computers are not connected to the VPN. Forefront Unified Access Gateway (UAG) 2010 extends the benefits of DirectAccess across your infrastructure, enhancing scalability and simplifying deployment and ongoing management.
* Both L2TP and IPsec must be supported by both the VPN client and the VPN server. Client support for L2TP is built in to the Windows Vista® and Windows XP remote access clients, and VPN server support for L2TP is built in to members of the Windows Server® 2008 and Windows Server 2003 family.
* 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. SSL provides transport-level security with key- negotiation, encryption and traffic integrity checking. The use of SSL over TCP port 443 allows SSTP to pass through virtually all firewalls and proxy servers.