if you have worked in an ISP and have a Web acoount to your Main Providr -Class B or Class A Provider .. . you May see A Pic like this one Under here …
I Always wondered about what is that RADIUS ... all i knew before about the word radius is that it’s equivalent to half Diameter .. till i googled for the word and then i know that radius is a Server … and it’s very nice and important one and here what i got from google..
Radius is a server for remote user authentication and accounting. Its primary use is for Internet Service Providers, though it may as well be used on any network that needs a centralized authentication and/or accounting service for its workstations
GNU has Radius project ..
RADIUS = Remote Authentication Dial In User Service .
to know more about it …
GNU Radius Page
WikiPedia Radius Page
Aradial RADIUS server and this how it’s connected
Enjoy ..
and Hope it helps …