FreeRadius Accounting for Fortigate 311B

Hi, I’m trying to deploy FreeRadius as an accounting solution in my network. my scenario is like this:  [image attached] Fortigate Firewall is already integrated with Active Directory and may send authenticated requests to FreeRadius, which is as well integrated with Active Directory. The work to be done: 1. using NAS (Fortigate Firewall in this case) attributes to do the accounting;                                    2. Specifying special Active Directory groups in FreeRadius configuration to have Internet access.   May you help me with the solution or at least give me some hints? Thanks, Alireza Goftari