RADIUSProtokoll

The RADIUS (Remote Authentication Dial-In User Service) protocol is a client-server protocol designed for centralized authentication, authorization, and accounting management for users who connect and use a network service. Developed in the mid-1990s, RADIUS is widely used in network access servers, wireless LANs, and virtual private networks (VPNs) to manage user access and enforce security policies.

RADIUS operates on the User Datagram Protocol (UDP) and relies on a request-response model, where a Network Access Server (NAS) sends authentication requests to a RADIUS server, which then validates credentials and returns an access control decision. The protocol supports various authentication methods, including Password Authentication Protocol (PAP), Challenge-Handshake Authentication Protocol (CHAP), and Extensible Authentication Protocol (EAP), allowing for flexible security implementations.

Key components of RADIUS include the NAS, which acts as the client interfacing with end users, and the RADIUS server, which stores user credentials and enforces policies. Additional elements like RADIUS proxies and shared secrets ensure secure communication between the NAS and server. The protocol also supports accounting functions, tracking user sessions for billing and auditing purposes.

RADIUS is standardized by the Internet Engineering Task Force (IETF) in RFCs 2058, 2138, and 2139, with extensions defined in later documents. Its simplicity, scalability, and integration with existing network infrastructure make it a foundational protocol for network security. While newer protocols like Diameter offer enhanced features, RADIUS remains widely deployed due to its reliability and broad compatibility.