RADIUS

Remote Authentication Dial-In User Service (RADIUS) is a networking protocol, operating on port 1812 that provides centralized Authentication, Authorization, and Accounting (AAA or Triple A) management for users who connect and use a network service.

• Often used by Internet service providers (ISPs) and enterprises to manage access to the Internet or internal networks, wireless networks, and integrated email services.
• May incorporate modems, digital subscriber line (DSL), access points, virtual private networks (VPNs), network ports, web servers, etc.
• RADIUS is often the back-end of choice for 802.1X authentication as well.

Resources

• FreeRADIUS Technical Guide
• FreeRADIUS
• How RADIUS Server Authentication Works