RADIUS (Remote Authentication Dial-In User Service): A networking protocol that provides
centralized Authentication, Authorization, and Accounting management for users who connect and use a
network service. Widely used by ISPs (Internet service providers) and large organizations to manage
access to IP networks, APs, VPNs, Servers, 802.1x, etc. Uses a client/server protocol that runs in
the application layer, and can use either TCP or UDP as transport. Network access servers, the
gateways that control access to a network, usually contain a RADIUS client component that
communicates with the RADIUS server. Use UDP ports 1812 for authentication and 1813 for accounting,
can use TCP as the transport layer with TLS for security.