Question

New Network gets jammed up quick, Why?

I work for a small school who recently did some hardware upgrades but does not have the budget for an IT guy so I am helping out without much of a background in IT.
My problem is my network drastically slows down when about 20 chromebooks connect to an AP. It is to the point where the chromebooks even have trouble logging in or accessing a basic web page. When traffic is light on a typical laptop or iPad it usually runs at 80ish mb/sec for both upload and download.
What is the best way to troubleshoot where my problem is?
I am running:
12 - TP-link EAP120 access points in cluster mode leading to
3 - gigabit switches placed 1 per area connecting roughly 5 APs each leading to
A gigabit switch in the server room
The server
The firewall
The fibre Internet connection.

Other info: The server is a HP ProLiant ML350 G5 running Windows server 2003. All cabling is cat5e.

Side Note from recent test: I ran 20 chromebooks all at the same time running YouTube. The last couple started struggling to load pages or login. At that peak I checked the AP they were connected to and it was at 4% cpu and 51% for the ram. So I think the APs are fine and the problem lies elsewhere but I don't know where to go from here.

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Answer
All true.

WiFi is like the old phone party line. Only one thing can talk at one time so it will slow with each device that connects. As Chromebooks are very chatty the speed loss will be felt. Normal machines like iPads and notebooks cache content and will be less of a load.

By design, this all seems proper. Chromebooks will soak the WiFi and internet link.

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Answer
Now did you plan your WiFi?

Let's look at your common 802.11n issue. There's one non-overlapping channel at the usual 802.11n 40MHz OFDM setting. Here's the picture.


Did you design with this in mind? Did you try it with 802.11g?

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Channels Changed

This information on overlapping channels was helpful. I noticed some of mine were very much overlapping so I have changed them. I will now test to see if there is a performance improvement.

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Here's the app I use on my Android phone to see this.
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Troubles Continue

With the channels no longer overlapping as much there is a slight improvement but the troubles continue. Today I ran a test connecting 20 chromebooks to the network accessing the same AP. The AP was fine with similar values to OP. I used speedtest.net to check the speed and first few chromebooks to logon were running at 60mbps dl and up. By the time I had the 20th chromebook on the speed dropped to 0.1mbps.
I checked my wired computer at that time and it was running 99mbps.
I checked my laptop which was connected to the same AP but running through the Staff network and switches and it was running at a good connection.
Something happens down the line from the AP that causes a bottle neck slowdown. Potentially an issue in the switches but I have no clue how to test to see if the switch is the slow component.

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Now you know why I keep WiFi client counts limited.

Not only did you go for 20 clients but soaked the WiFi with youtube. Nice for stess testing but given how WiFi works (half duplex, only one client at a time) you know you are pushing the limit.

They usually cover this in networking classes. Here I limit connections to 16. Sometimes less.

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client counts

Fair point about the connections but by what you say that would mean that in a typical school classroom (30 students) there would need to be 2 APs. In a school building not only is that a ton of hardware but it also brings in major overlapping channel issues.

Do you know if there is a way to have APs reach a limit not in clients but in performance so that when a threshold is reached the next client cannot connect to that AP but rather connects to the next closest AP? This would spread the load a bit as in most locations there is the primary AP but I can also detect a relatively good signal from two other offset channel APs.

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Sorry no.

WiFi is not that advanced today. It still demands the user pick another AP if one is crowded. There are folk out there that want to automate this and let's hope they crack this nut. But as it stands today, nope.

You've seen the effect of what happens when too many WiFi things are in an area. The famous one is Steve Jobs telling the audience to switch off their phones and WiFi.

So here we are with an aging standard. Me? I wrote router code decades ago so I know more than I let on. My take is the industry needs a do-over.

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