[RFC][v1][Design] AP Architecture for Roaming with Wi-Fi 8 Seamless Mobility Domain (SMD)

[Johannes Berg]

Hi,

Some quick feedback since I'm going on vacation for the next ~week ...

Would be nice btw to get feedback on the NPCA stuff I posted, now that
you can apparently talk about UHR ;-)

>         [2.3.2] Endpoints
>         -----------------
> 	To enable faster and more scalable SMD roaming, we propose placing the
> 	endpoint for Inter-AP (IAP) SMD messaging in kernel space, rather than
> 	relying on hostapd-managed messaging as used in FT roaming.

I _really_ think you should _not_ design it that way right now. To the
point where I think I'm going to just reject adding that to mac80211 at
this stage, unless a real need can be demonstrated.

> 	The motivation for this design is to reduce latency during ST Execution,
> 	especially under max client concurrency and high system load and avoiding a
> 	direct impact on the data path transition.

That's not _really_ a good argument though - mac80211 will likely have
to process this in process context, likely acquire wiphy mutex, etc.

> 	DL/UL traffic transition latency to the target AP MLD depends on the IAP
> 	messages and the ST Execution Response arriving on time. Therefore, these
> 	actions should not have to wait for pending management frames to be handled.

A good part of this argument - "pending management frames" - really goes
back to hostapd's architecture and single-threadedness, but really I
don't think "hostapd's current architecture implies more latency"
implies "we must put this into the kernel."

johannes