Operation of a radius server

[Dave]

I was just hoping someone here could explain to me how the radius server
process works.
My situation will be authorizing for DSL.

I think the process is:  My DSL wholesaler gets requests for a logins
under my realm to their NAS, then sends it to me, then I send back a yes
or no answer.

My question is what information do I have to supply to my DSL wholesaler
and what information do I need from them? regarding authorization types
or encryption?

Any info would help a lot.

Thanks