STA                    AP              STA1                   STA2
   |                      |               |                      |
   |<------ Beacon -------|               |<------ Data -------->|
   |                      |               |                      |
   |---- Probe Req. ----->|               |<------ Data -------->|
   |<--- Probe Res. ------|               |                      |
   |                      |               |<------ Data -------->|
   |---- Auth Req. ------>|               |                      |
   |<--- Auth Res. -------|               |<------ Data -------->|
   |                      |               |                      |
   |---- Asso Req. ------>|               |<------ Data -------->|
   |<--- Asso Res. -------|               |                      |
   |                      |               |<------ Data -------->|
   |<------ Data -------->|               |                      |
   |<------ Data -------->|               |<------ Data -------->|

      (i) 802.11 Infrastructure mode         (ii) 802.11-OCB mode