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

1/24/2017

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 first article, we will be talking about 802.11v.

Presentation of IEEE 802.11v

IEEE 802.11v or BSS Transition is an amendment which was published in 2011 and added to the IEEE 802.11-2012 standards. The objective of this amendment was to develop extensions to the 802.11 MAC/PHY to provide network management for STAs including:

L2 management of attached stations
Monitoring the attached stations
Configuring the attached stations
Updating the attached stations

While the IEEE 802.11k amendment defined messages to retrieve information from the station, the ability to configure the station were not in its scope. So the 802.11v amendment is complementary to the 802.11k amendment.

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

IEEE 802.11v PAR document: Link
IEEE 802.11v Task Group activity: Link
Section "4.3.13 - Wireless network management" of the 802.11-2012 standard: Link to download the IEEE 802.11-2012 standard

Beacon of a Wi-Fi network NOT supporting 802.11v

Looking at a Beacon frame in order to find 802.11v support, we need to focus on the Extended Capabilities Information Element number 127 and look at the 4th bit of the 3rd octet. This bit is most commonly named the "BSS Transition bit".

Below is a look at a Beacon of a Wi-Fi network not supporting 802.11v. As you can see, the BSS Transition bit is set to "0".

Now, we are going to enable 802.11v support on this same SSID.

Configuration of 802.11v on a Cisco WLC

In order to enable 802.11v on a WLAN profile on a Cisco WLC, you need to

Navigate to the "WLAN" menu
Select the WLAN profile you want to modify in order to open up the configuration view
In the configuration view, select the "Advanced" tab
Finally, in the advanced tab, under the "11v BSS Transition Support" section, select the "BSS Transition" option as shown in the image bellow:

You can now apply and save your new configurations.

Beacon of a Wi-Fi network supporting 802.11v

Once the configurations have been applied and that the APs start broadcasting the new beacon frames, you are now able to see that the BSS Transition bit has been set to "1".

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

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

2 Comments

charles lucero

2/3/2017 20:40:41

Do you happen to have any real world experience enabling BSS and whether or not enabling this causes some anomalies in some clients. I suspect and hope that this is fairly benign to all clients and you don't need special drivers or settings. And more importantly not throw something at a client causing it to react strangely like erratic roaming or lack of roaming, etc... thanks for the blog.

François Vergès link

2/5/2017 22:29:01

Hi Charles,

I've never had problems myself but I have heard other engineers having problems enabling the feature. If you have control over the clients connecting to your WLAN infrastructure, I would advise you to test it out before enabling it on your production network.

Also, check out the follow up article I've written related to client support: http://www.semfionetworks.com/blog/how-to-check-if-a-client-device-supports-80211v

Thank you for reading!

François