When a client station sends a broadcast probe request frame with a wildcard SSID, how do APs respond?
When a client station sends a broadcast probe request frame with a wildcard SSID, how do APs respond?
When a client station sends a broadcast probe request frame with a wildcard SSID, all APs that hear the request should reply after waiting a Short Interframe Space (SIFS) with a probe response. This is because probe requests with a wildcard SSID are intended to prompt every AP in proximity to answer, allowing the client to become aware of all available networks.
I think A is correct. If multiple APs operate on the same channel, multiple APs will reply.
Explanation: Probe Request are sent to the broadcast DA address (ff:ff:ff:ff:ff:ff). Once a Probe sent, STA starts a ProbeTimer countdown & wait for answers. At the end of the timer, STA process the answer it has received. If no answers received, STA moves to next channel & repeats the discovery process. STA sending Probe Request may specify the SSID they looking (called directed probe request). Then only IBSS STA or AP support that SSID will answer. The SSID value can also be set to 0 (ie SSID field is present, but empty). This is called Wildcard SSID or Null Probe Request. Null probe request: A probe request without the SSID information. A client station that is looking for any SSID sends a probe request with the SSID field set to null. If a null probe request is sent, all APs that hear the request should reply by sending a probe response.
should be B, because you can only send a probe on 1 channel, so only 1 AP may reply.
You can have way more than one AP on a channel within Rx distance of the STA who will respond.
B is correct!