802.11 Protocol Architecture
Summary
The 802.11 MAC Layer specifies two primary medium access
methods: PCF and DCF. PCF is polling based and DCF is purely
contention based. Each medium access method has its advantages and
disadvantages, but DCF is clearly the most popular implementation in
the industry. Each access method has a set of frame types that are used
to coordinate data transfer between stations and access points.
Each station uses passive or active scanning (or both) to identify a
potential BSS with which to associate. After associating with an access
point, a station can send and receive data frames and roam between
access points. A solid understanding of duration values, backoff
procedures, contention windows, and mixed mode environments is
important to troubleshooting performance problems.
