What is Radius
Radius is an user authentication protocol and stands for Remote Authentication Dial-In User Service.
It’s described in RFC 2865 – RFC 2869. With Radius it is also possible to do Authorization and Accounting. Some guys already described the whole Radius stuff at Wikipedia (click here to view the article).

Popular Radius Servers are freeRadius, Cisco ACS, Microsoft IAS or OpenRadius.

So what is nRadius
There are already some free Radius implementations for several platforms.
One day I was challanged to transmit an Radius request from an ASPx webpage. I thought the Microsoft .NET framework would offer a suitable class – but I was wrong. Hopefully Microsoft will provide a class for that kind of stuff in the future – but until then nRadius is a good alternative.

nRadius is a free .NET class, providing a simple PAP encrypted Radius Client.