AAA: Authorization, Authentication and Accounting is a technology for intelligently controlling access to network resources, enforcing policies, auditing usage, and providing the information necessary to bill for services. Authentication provides a way of identifying a user, typically by having the user enter a valid user name and valid password before access is granted. The authorization process determines whether the user has the authority to access certain information or some network sub-domains. Accounting measures the resources a user consumes while using the network, which includes the amount of system time or the amount of data a user has sent and/or received during a session, which could be used for authorization control, billing, trend analysis, resource utilization, and capacity planning activities. A dedicated AAA server or a program that performs these functions often provides authentication, authorization, and accounting services.
CSACS Cisco Secure Access Control Server