AAAA refers to Authentication, Authorization, Accounting, and Auditing. It is used to refer to a family of protocols that mediate network access.
Two network protocols providing this functionality are particularly popular: the RADIUS protocol, and its newer Diameter counterpart.
In some cases, the term AAA has been used to refer to protocol-specific information. For example, Diameter uses the URI scheme AAA, which stands for Authentication, Authorization and Accounting, and the Diameter-based Protocol AAAS, which stands for Authentication, Authorization and Accounting with Secure Transport.
These protocols were defined by the Internet Engineering Task Force in RFC 6733 and are intended to provide an Authentication, Authorization, and Accounting (AAA) framework for applications, such as network access or IP mobility in both local and roaming situations.
While the term AAA has been used in such a narrow context, the concept of AAA is more widely used within the industry. As a result, it is incorrect to refer to AAA and Diameter as being one and the same.