Diagnosing Network Slowdown

E

ElectroPulse

Limp Gawd
Joined
Aug 19, 2013
Messages
129
Hello, all!

I'm working at a high school with a dorm where students live, and many of us teachers and staff members live.

Here's the situation: We have one access point for the dorm (ENH200EXT with antenna). The internet speed here is 272kbps. Our network is set up like this:
Internet->pfSense Router->Manageable switch->various legs of the network (computer lab, front office, and straight to dorm access point)

What I am trying to figure out is this: There are times (usually when the dorm students are allowed to access the internet, but sometimes even when it is disabled for them) that the ping from my laptop to the pfSense server is upwards of 3000ms. When I ping from any other leg of the network, it is the usually 1-3ms. So, I am convinced that it is the access point.

However, I am at a loss to why this could be. Based on what I've read online, the limit to the number of users that an access point can handle is just the maximum bandwidth (in this case 150mbps), rather than some number of clients.

Since our internet connection is only 272kbps, there's no way that internet traffic is bogging down the network.

Any ideas what could be the issue (and what to do about it), or how to diagnose it?

By the way, this is a very low-budget mission school I am working at, so if at all possible I would prefer to fix what we have, rather than buying new equipment (in my mind, the ideal setup would be run a fiber line from the main switch to the dorm where there is another switch, then split it off to 2-3 standard access points within the building. Unfortunately, that would cost money (particularly the second managed switch)).

Thanks!
ElectroPulse
 
How many users are connected to the AP?

You probably have too many clients on one AP. I'm only guessing here but it can probably only handle about 30 active clients, more if they are idle.

Just my guess without knowing anything else.
 
I was going to say, the limit on a single AP is not the bandwidth, it is the number of clients.

Most APs can handle around 20-30 clients before starting to get real wonky. The way the wireless protocols work, even clients not using any bandwidth still have a performance impact on the AP.
 
Thanks for the replies!

/usr/home said:
How many users are connected to the AP?

You probably have too many clients on one AP. I'm only guessing here but it can probably only handle about 30 active clients, more if they are idle.

Just my guess without knowing anything else.
Click to expand...

Grentz said:
I was going to say, the limit on a single AP is not the bandwidth, it is the number of clients.

Most APs can handle around 20-30 clients before starting to get real wonky. The way the wireless protocols work, even clients not using any bandwidth still have a performance impact on the AP.
Click to expand...

Hmm... I was wondering this, despite reading otherwise elsewhere (though it would make sense this way). Even at times where we only have a few clients accessing the internet (when it is blocked for students), the ping times are still crazy high. So sounds like this is indeed the slowdown.

May need to see about funding for getting regular APs put into the dorm...
 
ElectroPulse said:
Thanks for the replies!





Hmm... I was wondering this, despite reading otherwise elsewhere (though it would make sense this way). Even at times where we only have a few clients accessing the internet (when it is blocked for students), the ping times are still crazy high. So sounds like this is indeed the slowdown.

May need to see about funding for getting regular APs put into the dorm...
Click to expand...

"Regular APs" will suffer the same fate with too many clients. You need more APs with less power so you have less noise and use separate channels to try and split your devices between APs., 1,6,11 in North America on 2.4 GHz.

Also it looks like you are using an outdoor AP indoors? You may be overpowering the clients which can cause issues as well. You could try lowering your output power, but it sounds like too many devices per AP. Wireless devices all share the same media like a hub. The more devices chatter and try to use it at the same time, the more "collisions" and waiting needs to take place before a host can transmit and receive.

I believe Ruckus has APs that CAN handle over 100 clients but they are pricey. I suggest you look at Unifi APs. $80 a pop and they work great. You really won't find a better AP for that price. (In before people start recommending TP-Link routers as APs....)
 
They are blocked from the internet, but are they blocked from communicating with each other, they could easily be sharing content between each other....
 
Thanks for the replies!

/usr/home said:
"Regular APs" will suffer the same fate with too many clients. You need more APs with less power so you have less noise and use separate channels to try and split your devices between APs., 1,6,11 in North America on 2.4 GHz.

Also it looks like you are using an outdoor AP indoors? You may be overpowering the clients which can cause issues as well. You could try lowering your output power, but it sounds like too many devices per AP. Wireless devices all share the same media like a hub. The more devices chatter and try to use it at the same time, the more "collisions" and waiting needs to take place before a host can transmit and receive.

I believe Ruckus has APs that CAN handle over 100 clients but they are pricey. I suggest you look at Unifi APs. $80 a pop and they work great. You really won't find a better AP for that price. (In before people start recommending TP-Link routers as APs....)
Click to expand...
Actually, it is outdoors. We have it on a roof of a building about 300-500 feet (not a good judge of distances) from the dorm, and there the signal passes through many, many walls (the signal also extends to staff housing another few hundred feet away). So no, I don't believe that overpowering is an issue.

Ah, what I meant by "Normal APs" was indoor business-level ones (at least that was what I had a mental picture of when typing). Would get multiple indoor APs to spread throughout the dorm, and spread out the users on... Unfortunately, this goes back to the "Low-budget mission school" part, so hopefully can procure some funding (after thinking about it, I think I know of a good source).


MrGuvernment said:
They are blocked from the internet, but are they blocked from communicating with each other, they could easily be sharing content between each other....
Click to expand...

I have something called "Isolation" turned on in the AP, which sounds like it keeps them from communicating from each other... Haven't really tested it, though.
 
If possible, get a controller-based WIFI system. This way you can aggregate the configuration, management & monitoring of multiple AP's.
 
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