802.11r Roaming with Fast Transition (FT) 802.11r Roaming with Fast Transition (

802.11r Roaming with Fast Transition (FT)

AN13888

802.11r, roaming, bgscan, wpa supplicant, fast transition

NXP B.V.

802.11r Roaming with Fast Transition (FT)

Jul 1, 2024 — NXP Wi-Fi radios support IEEE 802.11r roaming implemented with Fast Transition (FT). Fast Transition is faster than normal roaming because it avoids a 4-way ...17 pages

PDF Viewing Options

Not Your Device? Search For Manuals or Datasheets below:

File Info : application/pdf, 17 Pages, 670.01KB

Document DEVICE REPORTAN13888

AN13888
802.11r Roaming with Fast Transition (FT)
Rev. 2 -- 1 July 2024

Application note

Document information

Information

Content

Keywords

802.11r, roaming, bgscan, wpa_supplicant, fast transition

Abstract

Introduces the types of fast transition and describes how to enable fast transition.

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

1 Introduction

NXP Wi-Fi radios support IEEE 802.11r roaming implemented with Fast Transition (FT). Fast Transition is faster than normal roaming because it avoids a 4-way handshake when transitioning from one AP to another. This documents explains how to enable the two types of fast transition.

1.1 Supported products
The following wireless SoCs support 802.11r:
· 88W8897 · 88W8987 · 88W8997 · 88W9098 · IW416 · IW611 · IW612
Note: Refer to the feature list in the respective product software release package to check that 802.11r is supported.

1.2 References
Table 1.Reference list Reference type Web page Application note Application note Application note

Description Open source wpa_supplicant (link) AN13296 - Embedded Wi-Fi Subsystem API specification v16 (link) AN13297 - Embedded Wi-Fi Subsystem API specification v17 (link) AN13538 - Embedded Wi-Fi Subsystem API specification v18 (link)

1.3 Notation conventions
This document employs the following notation conventions:
· Commands and examples of command outputs are shown in paragraphs with grey background color
This is an example of command
· Terms related to commands use a monospace font: parameter option command name
· File names, directory names and paths are shown in italics: <file name>.<extension> <directory> path/to/directory/and/file

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

2 Configuration
This section describes how to enable the fast transition feature.
2.1 Driver
When loading the drivers, use the following parameters to enable fast transition:
host_mlme=1 cfg80211_wext = 0xf (uAP and STA mask of CFG80211 and WEXT control)
Example of command to load the driver:
insmod mlan.ko insmod sdxxx.ko fw_name=nxp/<fw_name>.bin cfg80211_wext=0xf auto_ds=2 ps_mode=2
txpwrlimit_cfg=nxp/<power_table>.bin cal_data_cfg=nxp/WlanCalData.conf host_mlme=1 drvdbg=0x20037
Note: Setting dvrdbg = 0x20037 is optional and used to log FT messages on dmesg.

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

2.2 wpa_supplicant
Note: wpa_supplicant version 2.7 or above is required for Fast Transition. Step 1 - Enable IEE80211R parameter in hostap/wpa_supplicant/.config file

CONFIG_IEEE80211R=y Step 2 - Compile wpa_supplicant.

make
Step 3 - Edit wpa_supplicant.conf file Example of wpa_supplicant.conf content

ctrl_interface=/var/run/wpa_supplicant

ctrl_interface_group=0

update_config=1

ap_scan=1

network={

ssid="TEST_NETWORK"

key_mgmt=FT-PSK

<- Fast Transition Key Management

proto=RSN

pairwise=CCMP

group=CCMP

psk="1234567890"

bgscan="simple:30:-75:120"

<- Background scan settings

· Set key_mgmt parameter to FT-PSK or FT-EAP.

key_mgmt=FT-PSK key_mgmt=FT-EAP
· Set the background scanning parameters, bgscan bgscan="simple:<short scan interval >:< signal strength threshold>:<long scan interval>"
Where:

Parameter Short scan interval
Signal strength threshold Long scan interval

Description
Perform a scan every X seconds when the signal strength is weaker than the threshold
Signal strength from AP (dBm)
Perform a scan every X seconds when the signal strength is higher than the threshold

Example:

bgscan="simple:30:-75:120"
The example performs a scan every 30 seconds when the signal strength from the current AP is below -75 dBm. If the signal strength is above -75 dBm, the interval is every 120 seconds. Step 4 - Run wpa_supplicant.

wpa_supplicant -B -Dnl80211 -imlan0 -c/etc/wpa_supplicant.conf

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

3 Types of fast transition
The two types of fast transition are over-the-air and over-the-distribution-system (over-the-DS).
3.1 Over-the-air fast transition
In over-the-air fast transition, the STA directly communicates with the target AP using IEEE 802.11 FT-Auth and FT-(Re)Association during the fast transition association flow. The capability for fast transition is advertised in the Beacon Mobility Domain Information Element of the AP. Command to trigger fast transition over-the-air:
wpa_cli -i mlan0 ROAM <MAC address of Target AP >

3.2 Over-the-DS fast transition
In over-the-DS fast transition, the STA communicates with the target AP through the current AP. STA sends IEEE 802.11 FT action frames to the current AP which forwards the frames to the target. The capability for fast transition is advertised in the Beacon Mobility Domain Information Element of the AP. Note: Open source wpa_supplicant does not support automatic roaming over-the-DS. Command to trigger fast transition over-the-DS:
wpa_cli -i mlan0 FT_DS <MAC address of Target AP >

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

4 Examples
4.1 Over-the-air fast transition
To test over-the-air fast transition, follow these steps:
Step 1 - Configure the wireless LAN controller for Over-the-Air Fast Transition. Step 2 - Connect both Access points, AP1 and AP2, to the wireless LAN controller. Step 3 - Configure the DUT as described in Section 3.1 and 3.2 and connect the DUT to AP1. Step 4 - Move the DUT closer to AP2 until the signal strength from AP1 is less than the threshold Step 5 - Check that the sniffer capture has the following Over-the-Air sequence: 1. Authentication 2. Authentication 3. Reassociation request 4. Reassociation response
In this example, the wireless LAN controller is configured for over-the-air fast transition. The STA is connected to AP1 at location A. As the STA moves closer to AP2 at location B, the receive signal strength from AP1 drops below the set signal threshold. The STA automatically switches to AP2.
Figure 1 shows an example of over-the-air fast transition set-up. The arrows represents the over-the-air fast transition sequence:
1. Authentication 2. Authentication 3. Reassociation request 4. Reassociation response

Figure 1.Over-the-air fast transition set-up

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

Figure 2 shows a screen capture of Over-the-Air Fast Transition in a packet.
· AP1 MAC address of 08:cc:68:b4:2b:a0 · STA MAC address of 00:50:43:22:10:72 · AP2 MAC address of 08:cc:68:b4:2f:90

Figure 2.Screen capture of Over-the-Air Fast Transition packet
Example of dmesg log:
wlan: send out FT auth,wait for auth response wlan : FT response target AP 08:XX:XX:XX:2f:90 wlan: FT auth received Fast BSS Transition use ft-over-air wlan: Fast Bss transition to bssid 08:XX:XX:XX:2f:90 successfully

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

4.2 Over-the-DS fast transition
To test over-the-DS fast transition, follow these steps:
Step 1 - Configure Wireless LAN Controller for over-the-DS fast transition. Step 2 - Connect the access points AP1 and AP2 to the Wireless LAN Controller. Step 3 - Configure the DUT as described in Section 3.1 and 3.2 and connect the DUT to AP1. Step 4 - Move the DUT closer to AP2, where the signal strength from AP1 is less than the threshold. Step 5 - Run wpa_cli command to trigger over-the-DS fast transition.
wpa_cli -i mlan0 FT_DS <MAC address of Target AP>
Step 6 - Check that the sniffer capture has the following over-the-DS fast transition sequence: 1. Action frame (fast transfer request) 2. Action frame (Fast Transfer Response) 3. Reassociation request 4. Reassociation response
In this example, the wireless LAN controller is configured for over-the-DS fast transition. The STA is connected to AP1 at location A. When the STA moves closer to AP2 at location B, the receive signal strength from AP1 drops below the set signal threshold. STA is triggered to switch to AP2 when the wpa_cli command is issued (step 5)
Figure 3 shows over-the-DS fast transitions. The arrows represent over-the-DS fast transition sequence:
1. Action frame (fast transfer request) 2. Action frame (fast transfer response) 3. Reassociation request 4. Reassociation response

Figure 3.Over-the-DS fast transition set-up

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

Figure 4 shows a screen capture of over-the-DS fast transition in a packet with:
· AP1 MAC address: 08:cc:68:b4:2b:a0 · STA MAC address: 00:50:43:22:10:72 · AP2 MAC address: 08:cc:68:b4:2f:90

1 2 3
4

Figure 4.Screen capture of over-the-DS fast transition packet
Example of dmesg log:
wlan: send out FT request,wait for FT response wlan : FT response target AP 08:XX:XX:XX:2f:90 wlan: received FT response Fast BSS transition to bssid 08:XX:XX:XX:2f:90 successfully

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

5 Fast transition flow
The section includes illustrations of the interaction between wpa_supplicant, the Wi-Fi driver and the firmware. The wpa_supplicant commands (in upper case) are defined in hostap/src/drivers/nl80211_copy.h file. For more details about the driver to firmware APIs, refer to Embedded Wi-Fi Subsystem API Specifications (Section 1.2). Figure 5 shows the flow for over-the-air fast transition.

wpa_supplicant

driver

firmware

ROAM <BSSID> wpa_supplicant_associate

NL80211_CMD_AUTHENTICATE

AUTH frame

sme_event_auth EVENT_FT_RESPONSE
sme_associate
assoc Resp Received Update GTX

AUTH RESPONSE frame

NL80211_CMD_ASSOCIATE

HostCmd_CMD_802_11_ASSOCIATE

NL80211_CMD_ASSOCIATE_response

HostCmd_CMD_802_11_ASSOCIATE_response

NL80211_CMD_NEW_KEY

HostCmd_802_11_KEY_MATERIAL

Figure 5.Over-the-air fast transition flow

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors
Figure 6 shows the flow for over-the-DS fast transition.

AN13888
802.11r Roaming with Fast Transition (FT)

wpa_supplicant

driver

firmware

FT_DS <BSSID>
ft_rx_action PKT/PMK-R1 derived
sme_associate
Assoc Resp Received Update GTX

send_ft_action()

AUTH frame AUTH RESPONSE frame

NL80211_CMD_ASSOCIATE

HostCmd_CMD_802_11_ASSOCIATE

NL80211_CMD_ASSOCIATE_response

HostCmd_CMD_802_11_ASSOCIATE_response

NL80211_CMD_NEW_KEY

HostCmd_802_11_KEY_MATERIAL

Figure 6.Over-the-DS fast transition flow

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

6 Note about the source code in the document
The example code shown in this document has the following copyright and BSD-3-Clause license:
Copyright 2023-2024 NXP Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials must be provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

7 Acronyms and abbreviations

Table 2.Acronyms and abbreviations

Acronym

Definition

Access point

bgscan

Background scan

Distribution system

DUT

Device under test

Fast transition

MLME

Mac layer management entity

RSSI

Receive signal strength indication

STA

Station

wpa_cli

Command line interface to wpa_supplicant

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

8 Revision history

Table 3.Revision history Document ID AN13888 v.2 AN13888 v.1

Release date 01 July 2024 04 August 2023

Description · Changed the access from confidential to public. · Initial version

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

Legal information
Definitions
Draft -- A draft status on a document indicates that the content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included in a draft version of a document and shall have no liability for the consequences of use of such information.
Disclaimers
Limited warranty and liability -- Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. NXP Semiconductors takes no responsibility for the content in this document if provided by an information source outside of NXP Semiconductors. In no event shall NXP Semiconductors be liable for any indirect, incidental, punitive, special or consequential damages (including - without limitation lost profits, lost savings, business interruption, costs related to the removal or replacement of any products or rework charges) whether or not such damages are based on tort (including negligence), warranty, breach of contract or any other legal theory. Notwithstanding any damages that customer might incur for any reason whatsoever, NXP Semiconductors' aggregate and cumulative liability towards customer for the products described herein shall be limited in accordance with the Terms and conditions of commercial sale of NXP Semiconductors.
Right to make changes -- NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof.
Applications -- Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Customers are responsible for the design and operation of their applications and products using NXP Semiconductors products, and NXP Semiconductors accepts no liability for any assistance with applications or customer product design. It is customer's sole responsibility to determine whether the NXP Semiconductors product is suitable and fit for the customer's applications and products planned, as well as for the planned application and use of customer's third party customer(s). Customers should provide appropriate design and operating safeguards to minimize the risks associated with their applications and products. NXP Semiconductors does not accept any liability related to any default, damage, costs or problem which is based on any weakness or default in the customer's applications or products, or the application or use by customer's third party customer(s). Customer is responsible for doing all necessary testing for the customer's applications and products using NXP Semiconductors products in order to avoid a default of the applications and the products or of the application or use by customer's third party customer(s). NXP does not accept any liability in this respect.

Terms and conditions of commercial sale -- NXP Semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at https://www.nxp.com/profile/terms, unless otherwise agreed in a valid written individual agreement. In case an individual agreement is concluded only the terms and conditions of the respective agreement shall apply. NXP Semiconductors hereby expressly objects to applying the customer's general terms and conditions with regard to the purchase of NXP Semiconductors products by customer.
Suitability for use in automotive applications -- This NXP product has been qualified for use in automotive applications. If this product is used by customer in the development of, or for incorporation into, products or services (a) used in safety critical applications or (b) in which failure could lead to death, personal injury, or severe physical or environmental damage (such products and services hereinafter referred to as "Critical Applications"), then customer makes the ultimate design decisions regarding its products and is solely responsible for compliance with all legal, regulatory, safety, and security related requirements concerning its products, regardless of any information or support that may be provided by NXP. As such, customer assumes all risk related to use of any products in Critical Applications and NXP and its suppliers shall not be liable for any such use by customer. Accordingly, customer will indemnify and hold NXP harmless from any claims, liabilities, damages and associated costs and expenses (including attorneys' fees) that NXP may incur related to customer's incorporation of any product in a Critical Application.
Export control -- This document as well as the item(s) described herein may be subject to export control regulations. Export might require a prior authorization from competent authorities.
Translations -- A non-English (translated) version of a document, including the legal information in that document, is for reference only. The English version shall prevail in case of any discrepancy between the translated and English versions.
Security -- Customer understands that all NXP products may be subject to unidentified vulnerabilities or may support established security standards or specifications with known limitations. Customer is responsible for the design and operation of its applications and products throughout their lifecycles to reduce the effect of these vulnerabilities on customer's applications and products. Customer's responsibility also extends to other open and/or proprietary technologies supported by NXP products for use in customer's applications. NXP accepts no liability for any vulnerability. Customer should regularly check security updates from NXP and follow up appropriately. Customer shall select products with security features that best meet rules, regulations, and standards of the intended application and make the ultimate design decisions regarding its products and is solely responsible for compliance with all legal, regulatory, and security related requirements concerning its products, regardless of any information or support that may be provided by NXP. NXP has a Product Security Incident Response Team (PSIRT) (reachable at [email protected]) that manages the investigation, reporting, and solution release to security vulnerabilities of NXP products.
NXP B.V. -- NXP B.V. is not an operating company and it does not distribute or sell products.
Trademarks
Notice: All referenced brands, product names, service names, and trademarks are the property of their respective owners.
NXP -- wordmark and logo are trademarks of NXP B.V.

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

AN13888
802.11r Roaming with Fast Transition (FT)

Tables

Tab. 1. Reference list .................................................... 2 Tab. 2. Acronyms and abbreviations ........................... 13

Tab. 3. Revision history ...............................................14

Figures

Fig. 1. Fig. 2.
Fig. 3.

Over-the-air fast transition set-up ......................6 Screen capture of Over-the-Air Fast Transition packet ............................................... 7 Over-the-DS fast transition set-up .....................8

Fig. 4.
Fig. 5. Fig. 6.

Screen capture of over-the-DS fast transition packet ................................................ 9 Over-the-air fast transition flow ....................... 10 Over-the-DS fast transition flow ...................... 11

AN13888
Application note

All information provided in this document is subject to legal disclaimers.
Rev. 2 -- 1 July 2024

NXP Semiconductors

Contents

Introduction ...................................................... 2

1.1

Supported products ........................................... 2

1.2

References .........................................................2

1.3

Notation conventions ......................................... 2

Configuration ................................................... 3

2.1

Driver ................................................................. 3

2.2

wpa_supplicant .................................................. 4

Types of fast transition ................................... 5

3.1

Over-the-air fast transition ................................. 5

3.2

Over-the-DS fast transition ................................ 5

Examples .......................................................... 6

4.1

Over-the-air fast transition ................................. 6

4.2

Over-the-DS fast transition ................................ 8

Fast transition flow ........................................10

Note about the source code in the

document ........................................................12

Acronyms and abbreviations ....................... 13

Revision history .............................................14

Legal information ...........................................15

AN13888
802.11r Roaming with Fast Transition (FT)

Please be aware that important notices concerning this document and the product(s) described herein, have been included in section 'Legal information'.

Apache FOP Version 2.6