The June 2007 TechNet Cable Guy article in TechNet magazine, "The Secure Socket Tunneling Protocol," describes how the Secure Socket Tunneling Protocol (SSTP) in Windows Server 2008 uses the HyperText Transfer Protocol (HTTP) over secure sockets layer (SSL) for remote access virtual private network (VPN) connections across network address translators (NATs), firewalls, and proxy servers.
 
For additional resources about VPNs in Windows, see:

For a list of previous The Cable Guy articles, see
http://www.microsoft.com/technet/community/columns/cableguy/cgarch.mspx.
 
For the current issue of TechNet Magazine, see