RADIUS
RADIUS is the AAA protocol behind every enterprise Wi-Fi login, VPN authentication, and 802.1X deployment. FreeRADIUS, Cisco ISE, and Aruba ClearPass all implement it. Essential for understanding corporate network access and SSO integration.
What It Defines
Remote Authentication Dial-In User Service provides centralized AAA (Authentication, Authorization, Accounting) for network access. NAS/VPN servers/Wi-Fi APs forward credentials to a RADIUS server which returns Access-Accept, Access-Reject, or Access-Challenge. Uses UDP with MD5 HMAC authentication. Successor RADIUS over TLS (RFC 6614) fixes transport security.
Canonical (Normative)
Convenient (Practical)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
Diameter is the AAA backbone of LTE and IMS networks. If you build carrier infrastructure or work on 4G/5G billing and policy enforcement, you'll encounter Diameter on the S6a, Rx, Gx, and Gy interfaces.
TACACS+ is the standard for managing network infrastructure logins. Cisco, Juniper, and Aruba devices all support it. Any NOC that uses TACACS+ via Cisco ISE or Tac_Plus needs engineers who understand the AAA separation model.
802.1X is how enterprises authenticate devices before allowing network access. Required knowledge for corporate Wi-Fi, VPN alternatives, and zero-trust network access designs.