From the wikipedia page on RADIUS:
RADIUS is a client/server protocol that runs in the application layer, using UDP as transport. The Remote Access Server, the Virtual Private Network server, the Network switch with port-based authentication, and the Network Access Server (NAS), are all gateways that control access to the network, and all have a RADIUS client component that communicates with the RADIUS server.
Could someone tell me how many actual piece of hardware I would need on the client side if I wanted to offer public wifi? Do these components listed above come built into a router, or a firewall, or a switch etc? Or would I need some servers on the client side? I was hoping to only have an access point and then a gateway to the internet... and on the other side my RADIUS server, web server (containing captive portal webpage etc)?