QandAs: Tech

What is Radius?

Answer:
RADIUS, or Remote Authentication Dial-In User Service,

is a protocol used by servers on a network to provide centralized management of authentication, authorization, and accounting for workstations.

RADIUS was developed in 1991 by Livingston Enterprises, Inc., to provide server security. RADIUS sits at OSI Layer 5, the Application Layer, and uses Universal Datagram Protocol packets for transmission. It is often used by ISPs for its broad support and ubiquitous nature.

RADIUS transactions are two-way. A workstation sends a request to a Network Access Server, which then sends a RADIUS Access Request on behalf of the client machine. The RADIUS verifies the user's credentials and if they are legitimate, the RADIUS server grants the user access to network resources.

RADIUS servers are not as secure as TACACS+ servers because RADIUS servers use a shared secret password. This inherently becomes a security vulnerability in itself because some people tend to write down their passwords.