1. Wireless Fundamentals Examining Wireless Media Access

2. Sending a Frame 3. Sending a Frame (Cont.) 4. Sending a Frame (Cont.) 5. After a Frame Is Sent 6. 802.11 Frame Shape 7. Frame Types

• Management:

• • Beacon, probe request, probe response

• • Authentication request, authentication response

• • Association request, association response

• • Deauthentication, reassociation request, reassociation response

• • Announcement Traffic Indication Message (ATIM)

8. Frame Types (Cont.)

• Control:

• • Request to send (RTS), clear to send (CTS), acknowledgment (ACK),

• • Power Save Poll (PS-Poll),

• Data:

• • Simple data

• • Null function (empty frame)

9. 802.11 Frame Speeds 10. Discovering the Network (Mgmt Frames) 11. Connecting (Mgmt Frames) 12. Staying Connected (Mgmt Frames) 13. Control Frames

ACK is used after each frame.

RTS and CTS are used in 802.11b and g mixed cells and in hidden node situations. 14. WMM Enhancement 15. Power Save Mode 16. Summary

• Sending a frame requires a timing and acknowledgment system that is based on CSMA/CA.

• 802.11 frames have a specific shape with headers containing specific information and different parts that are sent at different speeds.

• Beacons and probes help discover the network.

• Authentication and association frames are used to join the cell.

• Some other management frames may be used while the client is connected.

• Control frames improve the communication framework by allowing special messages in specific cases, such as RTS and CTS or PCF.

• Some stations may use the power save mode to increase battery time, which means there must be specific exchanges with the AP.

17.