Chapter 11 IPsec VPN for FortiOS 5.0 : L2TP and IPsec (Microsoft VPN) : Overview
  
Overview
The topology of a VPN for Microsoft Windows dialup clients is very similar to the topology for FortiClient Endpoint Security clients.
Figure 281: Example FortiGate VPN configuration with Microsoft clients
For users, the difference is that instead of installing and using the FortiClient application, they configure a network connection using the software built into the Microsoft Windows operating system. Starting in FortiOS 4.0 MR2, you can configure a FortiGate unit to work with unmodified Microsoft VPN client software.