RADIUS

RADIUS, which stands for Remote Authentication Dial-In User Service, is a protocol developed to manage network access authentication, authorization, and accounting (AAA). Initially created by Livingston Enterprises in 1991, RADIUS has become a key protocol in modern networking, especially for authentication services provided by ISPs and enterprises.

RADIUS was designed to control dial-in access to computer networks, but it has since evolved to secure various forms of network access, including Wi-Fi and VPNs. It operates on the client-server model, where clients send requests to a RADIUS server that manages user credentials and network policies. The protocol operates over UDP, typically on port 1812 for authentication and authorization, and port 1813 for accounting. The core functions of RADIUS include verifying user credentials, enforcing network policies, and logging usage records. With its widespread adoption, RADIUS has also integrated with other protocols like EAP (Extensible Authentication Protocol) to provide more versatile authentication mechanisms. Despite its age, RADIUS continues to be foundational for network security, demonstrating its robustness and reliability over the decades.