This chapter provides an overview of how the IEEE 802.11 protocol operates. You may feel that understanding the way in which low-level messages are exchanged is not relevant to understanding security. If you are concerned only with setting up a secure network following the configuration instructions in the manual, you are probably right. But one purpose of this book is to explain the new security system of IEEE 802.11 in sufficient detail that you become convinced that it really has been well thought out and is thoroughly secure. Accepting that systems are secure on face value is less work but sometimes leads to disappointment. To understand the later sections of this book, you need a grounding in the basic standard. Hopefully just enough of that grounding is provided here, but not too much.