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Daniel Pfeffer wrote: Get a Wi-Fi network sniffer
Good idea - I use https://play.google.com/store/apps/details?id=com.vrem.wifianalyzer[^] which is brilliant for a free app - open source as well.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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Thanks for the suggestions and the time you took to answer  .Daniel Pfeffer wrote: Is the cabinet closed while the computers are in use?
Only wood. I took the APs out and put them in separate corners of the room without any improvement.
Daniel Pfeffer wrote: Check the channel width on the access points
I tested all possible configurations : overlapping chans, no overlapping chans, 20MHz, 40Mhz. Best results with chan 1 and chan 6 or 11, 20MHz, but still not sufficient.
Daniel Pfeffer wrote: You should see a high throughput on both laptops
With 2 laptops, 2 access points, I have up to 6Mo/s (tried 2 different access points of different brands that are respectively 300Mb/s and 500Mb/s capable), all good. It starts to go down when I have more than 3 laptops on one AP. Two bizarre things here : why only 6Mo/s where it should be at least 20, and why the breakdown when 4+ are connected...
Daniel Pfeffer wrote: Get a Wi-Fi network sniffer
Done as well, and most other chans are indeed used by the school neighbourhood, but with very, very little signal strength, so they are barely visible.
Daniel Pfeffer wrote: The issue may be the number of transmission collisions
Interesting. How can I avoid this ? Could load balance of limitations per device help ?
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Rage wrote: Daniel Pfeffer wrote: The issue may be the number of transmission collisions
Interesting. How can I avoid this ? Could load balance of limitations per device help ?
If you can't switch to 5ghz (lots more channels available); about all you can do is see if you can reduce transmit power on the access points and clients.
Wifi devices can only transmit 1 at a time on a channel [*]; meaning that counter-intuitively increasing transmit power in a crowded environment only makes things worse (you're seeing more devices transmit, so each devices share of the transmit time goes down).
[*] not strictly true in the latest versions of the wifi standard if every device in range is using it; in maybe 10 years that's the case this might actually be relevant. (But probably not because someone will have a cheap #InternetOfShit device on the network that saved $0.01 by using a 20 year old wifi module.)
Did you ever see history portrayed as an old man with a wise brow and pulseless heart, weighing all things in the balance of reason?
Is not rather the genius of history like an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful?
--Zachris Topelius
Training a telescope on one’s own belly button will only reveal lint. You like that? You go right on staring at it. I prefer looking at galaxies.
-- Sarah Hoyt
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Thanks.
The more I look at it, the more I think this setup with 16 pcs on wireless cannot work properly.
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You need better than cheapo wifi-N 2.4ghz anyway.
I hope the laptops are capable of doing better and it's just the access point that's an obsolete paperweight.
Did you ever see history portrayed as an old man with a wise brow and pulseless heart, weighing all things in the balance of reason?
Is not rather the genius of history like an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful?
--Zachris Topelius
Training a telescope on one’s own belly button will only reveal lint. You like that? You go right on staring at it. I prefer looking at galaxies.
-- Sarah Hoyt
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There are now 4 access points, 2 of them are 5GHz capable, and new. I am not sure about what features make an AP better than another one.
The hp laptops are only 2.4GHz capable, but I tried with 5GHz wifi usb dongles, to no improvement (in a setup with 1 5GHz AP and 4 laptops, the fourth laptop browser froze while they were trying to access the internet at the same time).
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That is what I had in mind as next step, but I was not sure if physically the Wifi at 2.4Ghz really can handle more than 8 clients - It is worth a try though, thanks.
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It's probably a built in limitation in the access point.
Both at home and at work I have Unifi access points, they have a limit of 127 clients per radio (so 254 in total), that should be enough. 
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The current APs are also 254 clients capable, but this apparently does not mean that they guarantee bandwidth.
A 300Mbit/s device = 37Mo/s one direction = 18Mo/s both directions, so 254 devices would get with 100% efficiency about 70ko/s each, which is ... quite slow. 
But 18Mo/s for 8 clients is still about 2Mo/s/client, which should be sufficient for accessing a file or even watching SD videos from the internet, so I do not understand why I run into problems.
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Bandwidth balancing certainly isn't built in to all access points.
This is a problem when using the hub model, clients are greedy, so when they receive a package they immediately send the next request allowing no room for other clients to use the bandwidth.
So if your AP doesn't have bandwidth balancing, it's the first to come that wins, the rest gets a timeout after some retries.
There are three solutions that I can see.
A) Get an AP with bandwidth balancing
II) Change the settings for TCP retries and/or timeout.
3) Block YouTube in the DNS.
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Thanks, Jörgen, I'l ltry this  . Two of the four available APs can be configured.Jörgen Andersson wrote: lock YouTube in the DNS.
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Here is another open-source monitoring tool: Cacti[^]
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What do you see when you connect to the routers' admin page? Just those laptop connections, or everyone else in the place with a phone connecting to the free WiFi?
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Only the laptops (and there is no free Wifi possibility - and even if, the Wifi is only activated when the cart is in use, so that would be a sporadic problem).
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I've just found my first processor bug. No, not on one of the big guys like ARM or Intel but still a decent find on the Rabbit family of processors. The bug seems to have been there from the earliest days and to find it 20 years later is quite unexpected.
I've always said that I like programs you debug with an oscilloscope and hardware bugs you find with a test program, but this is the first bug on silicon and not at board level.
The feeling is quite ecstatic (what a big nerd am I!)
Mircea
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But isn't this like "It must be a compiler bug!"
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Almost, but I have a hierarchy of esteem where at the bottom are software hacks (like me), compiler writers are some levels above and chip designers are almost at the top.
To find a bug so high up the food chain is exhilarating
Mircea
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Most probably not. Test again and again ask yourself again and again is it really the processor and not your side. Most probably you will find it is your side, this from experience from my side 
[Edit]
Otherwhise you can name the bug
modified 27-Mar-21 21:01pm.
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Quote: Most probably not. Test again and again ask yourself again and again is it really the processor and not your side.
I did and I'm fairly sure this is not the case. Filed a bug report and we'll see what happens. I don't have any qualms admitting my errors so I promise I'll post the "denouement"
Mircea
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Good luck then
modified 27-Mar-21 21:01pm.
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Mircea Neacsu wrote: I don't have any qualms admitting my errors so I promise I'll post the "denouement"
And if it turns out you were right, will we have to call you Mircea cel Mare?
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Quote: And if it turns out you were right,
Unfortunately that's not the case. It was just my misreading of documentation as @Randor pointed out[^].
Anyway, as they say, the journey is more important than the destination and this one was a fun one
Mircea
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