Wireshark: How to check if a Wi-Fi network supports 802.11k

Today’s exercice is simple: study the beacon frame and try to figure out what characteristics of the Wi-Fi network are advertised.

In this article, we will be focusing on IEEE 802.11k support.

Presentation of IEEE 802.11k

IEEE 802.11k-2008 or "Radio Resource Measurement" (not to confused with the Radio Resource Management used by Cisco Wireless LAN Controllers) is an amendment which was publish in 2008 and added to the IEEE 802.11-2012 standards. Various types of measurements are defined that enable 802.11 stations to request measurements from other stations. Information that needs to be measured to optimize the radio network. For example, with 802.11k, stations are able to assess how occupied or idle a frequency channel is. The corresponding request and report mechanisms, and the formats of the frames through which the measurement requests and results are communicated among stations, are defined by the 802.11k amendment.

If you want to learn more about how IEEE 802.11k, please read the following documents from the IEEE:

• ​IEEE 802.11k document: https://standards.ieee.org/findstds/standard/802.11k-2008.html
• Section "Clause 10.11 Radio measurement procedures" of the 802.11-2012 standard: Link to download the IEEE 802.11-2012 standard
• Section "Clause 11.11 Radio measurement procedures" of the 802.11-2016 standard: Link to download the IEEE 802.11-2016 standard

Beacon of a Wi-Fi network NOT supporting 802.11k

Looking at a beacon frame in order to find 802.11k support, we need to validate that these different information elements (IE) are there:

• The "Country" element
• The "Power Constraint" element
• The "Radio Management (RM) Enable Capabilities" element

If these information element are not present in the Beacon, the Wi-Fi network does not support 802.11k. Here is an example of a Beacon only advertising the "Country" element. As you can see , the "RM Enable Capabilities" and "Power Constraint" elements are missing.

Now we are going to enable 802.11k support on the SSID.

Configuration of 802.11k on a Cisco Wireless LAN Controller (WLC)

In order to enable 802.11k support on a WLAN profile on a WLC, you will need to:

• Navigate to the "WLAN" menu
• Select the WLAN profile that you would like to configure. This will open up the configuration view
• In the configuration view, select the "Advanced" tab
• Finally, in the "Advanced" tab, under the 11k section, check the following check boxes:
  • "Assisted Roaming Prediction Optimization" & "Neighbor List": the controller will create an optimized list of neighbors to send to the client
  • "Neighbor List Dual Band": By default, the neighbor list contains only neighbors in the same band with which the client is associated. This option allows 802.11k to return neighbors in both bands.

You can now apply and save your new configurations.

Beacon of a Wi-Fi network supporting 802.11k

Once the configurations have been applied and that the APs start broadcasting the new beacons frames, you are now able to see all the specific informations elements (IE):

Thank you for reading, in the next post, we will explain how to check if a Wi-Fi network is supporting 802.11r.

If you want to know how the client devices can take advantage of 802.11k to better roam, head over to Rasika's blog: 
mrncciew.com/2014/09/11/cwsp-802-11k-ap-assisted-roaming/

If you want learn how to check if a Wi-Fi network is supporting 802.11v, head over to this post:
www.semfionetworks.com/blog/wireshark-how-to-check-if-a-wi-fi-network-supports-80211v
​
If you want to optimize the way you use Wireshark to perform Wi-Fi analysis, head over to this post:
www.semfionetworks.com/blog/wireshark-most-common-80211-filters

Cheers'


written by François Vergès