WLAN Analysis with Wireshark (802.11 Radio Information, Part 4)

Let's continue to cover additional details on 802.11 Radio Information within a Wireshark capture.

(Wireless) Channel: channels are frequently accessed using IEEE 802.11 protocols. Take 2.4 GHz as an example, there are fourteen channels being designated here.

2.4 GHZ channel allocation
Channel 1: 2,412 MHz; Channel 2: 2,417 MHz; Channel 3: 2,422 MHz;
Channel 4: 2,427 MHz; Channel 5: 2,432 MHz; Channel 6: 2,437 MHz;
Channel 7: 2,442 MHz; Channel 8: 2,447 MHz; Channel 9: 2,452 MHz;
Channel 10: 2,457 MHz; Channel 11: 2,462 MHz; Chann12: 2,467 MHz
Channel 13: 2,472 MHz; Channel 14: 2, 484 MHz

However, depending upon the regulation in each country, some of the channels may not be available,

Let's grab any available example to make such justifications. The following diagram shows frame is in channel 6, 2,437 MHz.

At the same time, the below example can view different frames populated in wireless channel, such as 1,3,4,5,6,11, and 13.

For any specific Wireshark capture, if we would like to see the number of STAs attempt to communicate with a specific wireless channel, we could take advantage of Channel display filter (wlan_radio.channel). For example, the underneath example is "wlan_radio.channel ==1", and we can see around 7 STAs over there, where most of the frames are in Beacon frames.

However, within a similar timeframe, channel 6 is also significantly utilized. As you may realize that  "Probe Response" occupies fair amount of proportion.

The 2.4GHz band is broken up into 11 channels (1-11), each 20MHz wide. That inevitably brought a concern of  overlapping channels. When overlapping channels are used (2-5, 7-10 in 2.4GHz), any stations (STAs) on those channels will transmit independent of what is happening on the other channels, causing a degradation of performance. The following images hot indicates the STAs use channel 2~5 to perform wireless communication.

As you can interpret from that diagram, the above data is sorted by Channel number. However, if we take source STA as the index, then, we should notice that some STAs are swifting wireless channel changes.

Auto Channel is a common management feature in some of the APs. By doing so, those AP would use less busy channels, in order to provide better services to wireless clients.

Quiz Review: The following diagram is a sorted result with the filter of "wlan_radio.channel >= 7 && wlan_radio.channel <= 10", how many identical STA(s) you are able to clarify?