Authorization, Authentication, and Accounting (AAA) is not a protocol, but a framework for ensuring access controls on a network by assigning policies and enabling the logging of activities. Authentication handles the mechanisms used to ensure that someone can prove their identity on a system before gaining access to the resource, such as providing a username (identity) and password combination. Authorization handles the assignment of privileges and policies to an authenticated user. Lastly, accounting is applied, which ensures that logs are generated for each action that is performed by the user.
Authentication concepts
Remote Authentication Dial-In User Service (RADIUS)
RADIUS is a client-server protocol that provides AAA...