Should hostapd 802.11r defaults be tweaked? (reassociation deadline, FT over ds/air)

[Hannu Nyman]

Based on forum discussion, I tested 802.11r with my routers and noticed that 
the current OpenWrt defaults (reassociation deadline 1000 ms and "FT over 
DS") do not really work. I was unable to get my Android devices to realiably 
roam with those values.

Switching to FT over Air and lengthening the reassociation deadline to 20000 
(20 seconds) made the devices to roam well.

There has been corroborating forum discussion that "FT over air" and reassoc 
20000 generally works.

I wonder if we should change our defaults.


Does anybody have qualified opinions/experience on the matter?


Source:

https://github.com/openwrt/openwrt/blob/master/package/network/services/hostapd/files/hostapd.sh#L810-L811


Bug discussing this: https://bugs.openwrt.org/index.php?do=details&task_id=3159

Forum references:

* 
https://forum.openwrt.org/t/802-11r-fast-transition-how-to-understand-that-ft-works/110920

* 
https://forum.openwrt.org/t/rekeying-issue-driver-can-t-safely-do-that/106579/18

*https://forum.openwrt.org/t/when-does-802-11r-ft-over-ds-make-sense-to-use/88893


Commits introduced the default values without much reasoning, as the main 
thing was the 802.11r key automatics:

https://github.com/openwrt/openwrt/commit/3cc56a5534b8b49a7e9ba57edf9878ec32bdd27a
https://github.com/lede-project/source/pull/1382

The commit picked the smallest value 1000 of the allowed time range of 
1000-65335.
E.g. Cisco seems to recommend 20000 = 20 seconds.


And regarding FT over DS, the commit introduced the feature and immediately 
switched the default to be it:

https://github.com/openwrt/openwrt/commit/b0d2c4ac417d54d18d0c5ab0a106f05657138ae0