Limit ADSL speed using radius?

Hi all, How can one limit the ADSL speed on a per customer basis using freeradius? I have been trying a radiusReplyItem: Microtik-Rate-Limit += 512k/1024k, which people recommend, but it does not look like it is working. I have been surfing the freeradius wiki for days now but no luck. I am using freeradius2-2.1.12-3.el5. Regards, To read FirstRand Bank's Disclaimer for this email click on the following address or copy into your Internet browser: https://www.fnb.co.za/disclaimer.html If you are unable to access the Disclaimer, send a blank e-mail to firstrandbankdisclaimer@fnb.co.za and we will send you a copy of the Disclaimer.