Hello Stefan, sorry for the late reply, find my comments below.
On Wed, Nov 3, 2021 at 4:47 PM Stefan Sperling <[email protected]> wrote: > On Wed, Nov 03, 2021 at 04:03:08PM +0300, Sergey Ryazanov wrote: >> This topic was discussed a couple of weeks ago on the hostapd mailing >> list (http://lists.infradead.org/pipermail/hostap/2021-October/039961.html). >> And Jouni Malinen provide a few concerns about switching to the QBSS >> load IE usage. I would like to quote him: >> >>> I would also point out that at least the last time I did some testing >>> between vendor implementations, the reported values were completely >>> different between two APs on the same channel in more or less the same >>> location in the test setup.. In other words, I would not place much, if >>> any, trust in this value being something that could be compared between >>> two different APs. The only thing that seemed to be more or less >>> comparable was the values from the same AP device in a sense that the >>> channel load value increased when there was more traffic on the >>> channel.. >> >> So I do not think that the complete switching to the BSS load metric >> is a good idea. But utilizing the AP assistance in the BSS selection >> procedure sounds nice. > > My patch ignores RSSI on purpose in case BSS load is advertised precisely > because we need to figure out whether "channel load" is indicated reliably. > The standard doesn't really go into much detail about how to decide whether > a channel is "busy". It suggests that either virtual or physical carrier > sense could be used. I guess just letting any faint but valid wifi signal > block the channel would be a bad idea. So vendors may need to use some > threshold to decide whether a given signal is actually keeping the channel > busy in the vicinity of the AP. As with RSSI, measurements of such physical > quantities could differ between any two given APs and between moments in > time for a single AP. > > If channel load is not a reliable indicator I would hope vendors are at > least able to reliably count and report the number of associated stations? The number of associated stations is a comparable metric. But it provides no information about the channel utilization. Consider two APs: one with 10 associated but idle smartphones and one with two laptops that receive a 20 mbit/s video stream each. It is better to connect to the first AP with the idle channel, but the stations number metric directs us to quite loaded AP. -- Sergey
