For the road travelers in the United States, especially the parents who take their children in the family car on the long road trips, the letters AAA stand for a peace of mind. They feel that any time their car breaks down, they can call the number for the American Automobile Association and ask for roadside assistance. Even though this book is not about that sort of AAA, the 3 "A"s that we talk about here, when designed properly, can bring the same peace of mind to the network operator and its customers. Authentication, authorization, and accounting are three important blocks used in the construction of a network architecture that helps protect the network operator and its customers from fraud, attacks, inappropriate resource management, and loss of revenue.
In this chapter, we describe each of the "A"s in the AAA first as a separate topic, and then as a piece that interacts with the other "A"s in an effort to justify why all the 3 "A"s should be treated by the same framework and servers. At the end of the chapter, we provide a model for a generic AAA architecture.