fair usage policy best practices

[Ali Arslan]

Hi,
I am a newbie in freeradius.
My radius server should handle multiple NAS devices from multiple vendors (Cisco, Mikrotik, juniper).
I want to implement FUP (fair usage policy),
Every user may buy different rates and fair usage limits, after he/she downloads fair usage limit quantity the rate will be lower.

I see 2 options:

1- An application that checks periodically the download quantities of users and and send SSH command to server to request CoA  from NAS like:
    echo "User-Name={UserName}, Rate-Limit={RateLimit}" | radclient NAS-IP:coaPort CoA secret

2- Unlang code in default site accounting section


In first option the check period should be low enough so that users wont download too much excess of their limit, this will hang server.

I need your suggestions about  best practices for FUP, and some instructions if second option is suggested.

a. arslan