FreeRADIUS Technical Guide

Chapter 1 - Introduction

This chapter describes:

What is RADIUS?What is FreeRADIUS?FreeRADIUS benefitsFreeRADIUS case studies

1.0 What is RADIUS?

RADIUS, which stands for “Remote Authentication Dial In User Service”, is a network protocol - a system

that defines rules and conventions for communication between network devices - for remote user

authentication and accounting. Commonly used by Internet Service Providers (ISPs), cellular network

providers, and corporate and educational networks, the RADIUS protocol serves three primary functions:

Authenticates users or devices before allowing them access to a networkAuthorizes those users or devices for specific network servicesAccounts for and tracks the usage of those services

For a detailed look at how RADIUS performs these functions, see section 2.2, “The RADIUS Session

Process”, on page 11.

1.0.1 History

In 1991, Merit Network, a non-profit internet provider, required a creative way to manage dial-in access to

various Points-Of-Presence (POPs) across its network. In response to this need, RADIUS was created by

Livingston Enterprises.

At the time RADIUS was created, network access systems were distributed across a wide area and were

run by multiple independent organizations. Central administrators wanted to prevent problems with

security and scalability, and thus did not want to distribute user names and passwords; instead, they

wanted the remote access servers to contact a central server to authorize access to the requested system

or service. In response to contact from the remote access server, the central server would return a

“success” or “failure” message, and the remote machines would be in charge of enforcing this response

for each end user.

The goal of RADIUS was, therefore, to create a central location for user authentication, wherein users from

many locations could request network access.

The simplicity, efficiency, and usability of the RADIUS system led to its widespread adoption by network

equipment vendors, to the extent that currently, RADIUS is considered an industry standard and is also

positioned to become an Internet Engineering Task Force (IETF) standard.

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