- 2074 Bhadra · 5 marks
RADIUS server and its functions
Short answer
A RADIUS server provides centralized AAA: authentication via PAP/CHAP/EAP, authorization with attributes like IP/VLAN/limits, and accounting for billing. It also centralizes user management and can proxy requests to other RADIUS servers, e.g. for roaming.
Explain RADIUS server with its functions.
RADIUS (Remote Authentication Dial-In User Service) is a networking protocol and server (RFC 2865/2866, UDP 1812/1813) that gives centralised Authentication, Authorization and Accounting (AAA) for users connecting to a network. Instead of storing user accounts on every dial-up server, VPN gateway, router or Wi-Fi access point, they are kept at one RADIUS server (or in LDAP/Active Directory behind it).
User --> [NAS: AP/VPN/dial-up] --RADIUS--> [RADIUS server]
(RADIUS client) |
user database
Working: the user connects and gives credentials. The Network Access Server (NAS), acting as RADIUS client, sends an Access-Request. The server checks the database and replies Access-Accept, Access-Reject or Access-Challenge. The NAS then lets the user in with the stated settings. The shared secret between NAS and server protects the messages.
Functions
- Authentication: verifies identity using PAP, CHAP, MS-CHAP or EAP (802.1X for Wi-Fi and wired ports).
- Authorization: decides what the user may do and sends attributes: IP address to assign, VLAN, session timeout, access lists, bandwidth limits, allowed services.
- Accounting: records session start and stop, duration, bytes in/out and the user's identity (Accounting-Request), used for billing, auditing and usage reports.
- Centralised management: one place to add, change or disable users for many access devices.
- Proxying: can forward requests to other RADIUS servers (realms), supporting roaming between organisations (e.g. eduroam).
Typical uses: ISPs, hotspots, corporate Wi-Fi, VPNs. Open source server: FreeRADIUS.
✓ Answer checked by Claude Opus 5.5 (high effort)