The IEEE 802.11 standard defines the authentication service, frames, and associated semantics for achieving this function. Chapter 4, "WLAN Fundamentals," discussed the general frame elements and the top-level choreography of authentication. This chapter concentrates on the payload and the next-level details of the authentication process.
Figure 5-1 shows the elements in the authentication frame body.
The authentication frame body consists of the algorithm number, transaction sequence number, status code, and challenge text. Two algorithms are supported now (as of this point in the evolution of the standards): open (number=0) and shared key (number=1). The challenge text element has the ID 16.
Authentication can be between a client's station (STA) and an AP or between two clients' STAs in the case of ad-hoc networks.