802.11r enabled on both bands per AP doesnt work

michael-dev michael-dev at fami-braun.de
Wed Jul 26 08:48:02 PDT 2017


802.11r is for roaming between BSS within an ESS (IEEE 802.11-2016 
section 13.1 second sentence).

When an AP sends on multiple frequencies, it usually spans multiple BSS. 
So for roaming to be possible, these BSS need to part of the same ESS 
and thus share the same SSID. For FT, they also need to share the same 
mobility domain identifier.

802.11r cannot be used for band steering, that is the AP forcing a 
client on a different band, as the client alone decides whether it roams 
or not.

Further possible issues:
  - a client might not choose to roam depending on its policy (which 
might depend on signal strengh or limit the band)
  - using different hostapd procceses on the same AP for each band needs 
extra steps for local RRB communication
    (and depending on your hostapd version also when both bands are 
managed from the same hostapd process)

How did you test 802.11r roaming? What do you observe when the client is 

M. Braun -> PMK-R0 derived from SSID

Am 24.07.2017 00:52, schrieb Deviance:
> 802.11r on one band (2,4GHz or 5GHz) per AP works with:
> mobility_domain=e612
> nas_identifier=<unique per BSS>
> ft_psk_generate_local=1
> wpa_key_mgmt=WPA-PSK FT-PSK
> While using those parameters for both bands per AP, client wont roam
> to higher/lower frequency on the same AP, neither to the other AP. It
> looks like the client is stuck.
> Am I misunderstanding the whole concept here: FT can only be used for
> clients to roam between APs and not bands on the same AP or are the
> parameters incorrect for this setup (both bands per AP)?
> hostapd v2.7-devel
> latest LEDE trunk
> Archer C7 v2 (all APs)
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