Basic Concepts of AAA
AAA Architecture
AAA uses the client/server model. The AAA architecture features good scalability and facilitates centralized user information management. Figure 1-1 shows a typical AAA system.
Authentication Modes
AAA supports the following authentication modes:
Non-authentication: All users are trusted without passing a validity check. This mode is rarely used.
Local authentication: User information is configured on the network access server (NAS). This mode features fast processing and low operation cost. However, the amount of local authentication information that can be stored is subject to the device hardware capacity.
Remote authentication: User information is configured on the authentication server. AAA can remotely authenticate users through the RADIUS or HWTACACS protocol.
Authorization Modes
AAA supports the following authorization modes:
Non-authorization: gives authenticated users unrestricted access and rights on a network.
Local authorization: authorizes users according to the attributes configured on the NAS for the local user accounts.
HWTACACS authorization: authorizes users through the HWTACACS server.
RADIUS authorization: Users pass the RADIUS authorization upon passing the RADIUS authentication. RADIUS integrates authentication and authorization. Therefore, RADIUS authorization cannot be performed separately.
- If-authenticated authorization: applies to scenarios where users must be authenticated and the authentication process is separated from the authorization process. For this reason, this mode is available for only local authentication and HWTACACS authentication, but not RADIUS authentication.
- After local authentication is successful, local authorization is used.
- After HWTACACS authentication is successful, all rights are enabled. That is, HWTACACS authorization is not required.
Accounting Modes
AAA supports the following accounting modes:
Non-accounting: gives users access to a network without being recorded or charged.
Remote accounting: supports remote accounting through the RADIUS or HWTACACS server.