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7.21 Support for 802.11r and 802.11v STA mode

The seamlessness of client roaming/steering is enhanced by implementing the following capabilities.

  1. 802.11r Fast BSS transition (over the air only) capability for STA mode. By having this implemented, the amount of handshakes between “nodes” is reduced.
  2. With respect to 802.11v, the capability for the master node to determine whether a slave node must connect to master node directly or through another slave node is implemented.

7.21.1 Design overview

FT initial mobility domain association The following are the steps performed by supplicant and driver during FT initial mobility domain association:

  1. Create 11r enabled STA VAP. To create this STA VAP, set option ‘ieee80211r’ to 1 in wireless configuration file.
  2. Supplicant performs scan, searching for AP with FT enabled (looking out for Mobility domain IE in Probe responses).
  3. After a suitable AP is detected, the supplicant issues a connect request to driver using cfg80211 interface.
  4. Driver performs FT initial mobility domain association with the selected AP and reports back the connection result (success or failure) to supplicant. On failure, the supplicant continues with the scan operation.

Over-the-air FT Roam

The following are the steps performed by supplicant and driver during over the air FT roam.

  1. Roam scan is triggered through supplicant by an application monitoring the link rssi.
  2. Roam candidate is selected by the supplicant.
  3. The supplicant updates FT IEs in driver.
  4. The supplicant issues connect request with selected roam BSSID to driver.
  5. The driver initiates roam and reports received FT IEs from AP to supplicant. Supplicant makes uses of these IEs to derive keys and update the driver.
  6. The driver completes the roam and updates the status to supplicant.

FT Roam using WNM (11v)

The following are the steps to trigger a BSS transition using WNM:

  1. Connect WNM client with WNM capable AP which is FT enabled.
  2. Trigger a BSS transition request from AP for the connected client to a target AP with same mobility domain and FT capable.
  3. Client receives a BSS transition request action frame and sends to wpa_supplicant.
  4. wpa_supplicant initiates a scans and if targeted AP is found in scan list and targeted AP is FT capable, then initiates a FT roam.
  5. Clients perform a successful FT roam to targeted AP.