Half of class can't connect to wireless

[davis1021]

I provide support to a Primary school who are having problems with their wireless. When a class is logging on (appox 20-30 laptops) around 5-10 are having issues with the network.

 

This tends to be mainly not having shares/redirected folders etc.

 

After a quick look yesterday i noticed the AP's were only accepting 8 clients each. So the class using the laptops at the time had 8 clients on 2x AP's and 5 on another with the rest dropping out.

 

I dont know if it's a case of simply re-configuring the AP's or something? They are set to AP mode but there is also repeater mode, multi-point mode etc etc. also, not sure if it may be channel setup too?

 

any help would be great

[davis1021]

AP's are Edimax EW-7416APn V2

[K.C.Leblanc]

To be honest if you want to be able to use that number of laptop reliably in a small space you will need a managed wireless system. And you will probably need 3 aps.

 

Look at Aruba and Ruckus.

[davis1021]

thanks but im pretty sure the school wouldnt go for the cost of them. is there any way i could use the existing AP's?

[Jamo]

We have an unmanaged system here, we can only use 10 -12 laptops before its unusable. Only way around it is to have different SSID's on the AP's and have the laptops connect to specific AP's rather than for them to find the strongest signal, it will evenly spread them then. As for the max number of clients check that there isn't any "load balancing" on the AP as some unmanaged ones just use this as a limit to how many clients they can have and don't "do" load balancing at all.

[davis1021]

if 2 AP's were next to each other with the same channel but different SSID would that be ok or still conflict?

[Jamo]

Still conflict, you could create a lot of cross talk. Would suggest spreading out the APs around the room and having channels 1 6 and 11 in use on the 3 APs. This gives the greatest chance of success with unmanaged APs.

[davis1021]

looks like im pretty much resigned to a managed network. what is it that makes the key difference between managed and unmanaged in terms of capability and clients connecting?

[BatchFile]

tbh I'd expect them to interfere like mad - like dropping two stones into a pond and expecting twice as many perfect rings.... one on each side of the room on different channels but the same ssid may work better as the laptops will go blindly for the strongest signal

 

EDIT: D'oh someone beat me to it

[BatchFile]

looks like im pretty much resigned to a managed network. what is it that makes the key difference between managed and unmanaged in terms of capability and clients connecting?

 

Well, our Ruckus APs can take, well, I don't know how many connections each, we've been up to 60 on one AP and it was still happy

They also talk intelligently to each other so the laptops can roam efficiently between them.

 

Rather than having just one arial they have loads of bits of areial that they combine to form "beams" by carefully manipulating interference patterns - and fire the signal straight at where it's needed!

[K.C.Leblanc]

There's more info here.

 

IEEE 802.11 - Wikipedia, the free encyclopedia

 

1, 6 and 11 are the three non overlapping channels make sure your APs are set to one of these channels and that you assign the channels in such a way that APs using the same channel are out of range of each other.

 

You will need 3 aps to support that many laptops. Bare in mind that the 56mb/s bandwidth for wireless is shared between all the laptops on the same AP. So if you managed to get 15 laptops on an AP they'd only have about 4mb/s bandwidth.

 

There are many users on here who invest thousands in good managed wireless, I doubt they'd do it if they could achive the same result using a couple of £25 APs.

[BatchFile]

I'm one of them - before we got Ruckus I was pretty impressed with what the unmanaged wireless could do, but it could never cope with more than 10 or so connections at once, though we did occasionally stretch to 15 in a room with an access point or two actually in the room.

But managed is definately the way to go "sit I can't log on it says the domain's unavailable" has been consigned to history! - and you (almost) get a Harry Potter style "marauder's map" with all the laptops on it to boot!

[davis1021]

think its gonna have to be a managed network, there's not enough network points in the rooms to go down the multiple AP's per room route

[K.C.Leblanc]

think its gonna have to be a managed network, there's not enough network points in the rooms to go down the multiple AP's per room route

 

Post up your location, there might well be a school near you who has a setup you can have a look at.

[BatchFile]

if it's just one room, IIRC you can run a single ruckus AP standalone without the management stuff for a few hundred quid (£250-£400 range)

[davis1021]

its about 12 rooms on 2 floors, 6 down 6 up in a long row. any guestimates on approx price?

[BatchFile]

£2-3k or so? you'll (depending on your building's construction) probably need 1 AP in the second and fifth rooms on each floor, so there's always an AP either in the room, or next door. We got ours from CPLTD (Sponsors on here), who were great throughout.

[davis1021]

just a quick update on this problem. had an engineer visit the site from a local network specialist and he did a site survey. he found that the site itself is fine (building material and such) and that the wireless range and speeds were fine.

 

conclusion was he didn't have a proper answer and he is contacting 3com to see what they say.

 

I am still sceptical I have the AP's set up correctly, the engineer said i did but... the 6 AP's are set to access point mode and they are each running DHCP as I cant get the clients to pick up DHCP from the server through the AP. now I'm not sure whether this is right or would something like repeater mode or multi-point mode be better?

 

Driving me mad!!!

[Jamo]

So you have loads of DHCP servers? Could they be dishing out the same IP more than once? I would say that the AP's are just swamped, quite frankly unmanaged systems quickly become unmanagable with anything more than a few users.

[davis1021]

thanks jamo.

 

the engineer wasn't too sure a managed system would help? he spoke of a controller to go in the switch rack but thought the wireless shouldnt need it. you think i should try getting the dhcp to work using the server instead of each AP?

 

think i might get another company to come in and have a look

[localzuk]

The devices you've bought are consumer grade AP's, not really designed for the use you're putting them to.

 

I'd be saying the same as others here - get a Managed system such as Ruckus. A 1006 controller, and 4 AP's would cover your site from the sounds of it. It'd come to about £2.5k for a good a/b/g/n solution (cheaper if you don't want n etc...).

 

The simple case is in a cheap unmanaged system you'll end up with lots of wireless collisions when more than, say, 8 or so devices try to connect to a single AP. This means each device just ends up having to re-send their requests over and over, effectively blocking communications. Managed systems generally overcome this, via various means.

 

Another way to look at it is this - if you have a single a/b/g AP, you effectively get 54Mbps speed shared between all the devices connected. So, if you have 10 devices you end up with 5.4Mbps each, minus overheads etc... Not much.

[apeo]

If you dont have too many APs, personally i wouldnt think having a managed system would help with connectivity. Managed system would make things alot easier to configure but wouldnt necessarily improve connectivty. It took quite abit of configuring to get our managed system to work here and there was a period when our previous unmanaged system was better (taken quite abit of configuring over a long time to get some dead spots to work, and now it works most of the time with random errors).

[localzuk]

Apeo - you've not used Ruckus then

 

Managed systems generally include extra things on top of the easy configuration - such as the complex antennae in Ruckus AP's, or the 'blanket' coverage used by Extricom, or IPSec VPNs built in to Aruba. There are many reasons a managed solution would help - all you have to do is test one out and you'll see a massive difference in terms of connectivity.

 

It really does depend on the system though. Ruckus manages, from various people on here, to get around 90 laptops all streaming things from bbc iplayer through 1 AP. Try that on a normal unmanaged AP, and you'll see nothing.

[apeo]

Apeo - you've not used Ruckus then

 

Managed systems generally include extra things on top of the easy configuration - such as the complex antennae in Ruckus AP's, or the 'blanket' coverage used by Extricom, or IPSec VPNs built in to Aruba. There are many reasons a managed solution would help - all you have to do is test one out and you'll see a massive difference in terms of connectivity.

 

It really does depend on the system though. Ruckus manages, from various people on here, to get around 90 laptops all streaming things from bbc iplayer through 1 AP. Try that on a normal unmanaged AP, and you'll see nothing.

 

Ruckus gets alot of praise and quite rightly so when it works but we are one of those that have found it to be a real pain. Ruckus doesnt play well with other APs, I've actually be told by a few providers this is the case, so if you have a lot of home broadband in the area guess what... problems. A lot of the cool features had to be turned off and pretty much our entire network is manually configured.

 

Looking at the problem davis1021 is having a managed system i guess would load balance and ruckus APs can potentailly handle quite a few connection before it becomes unstable. However are these APs installed in room or do they follow the laptops. If they follow the laptops then you could have 2 APs in the room on a different SSID and Channel (as suggested earlier). Then you can manually configure the laptop to connect to the one fo the SSID, manual load balancing if you will. This is the problem of having an unmanaged system, all these kind of things have to be done manually.

 

EDIT: I forgot to add, as stated you shouldnt configure DHCP on the APs and the clients get it from the server.

[_BC_]

 

1, 6 and 11 are the three non overlapping channels make sure your APs are set to one of these channels and that you assign the channels in such a way that APs using the same channel are out of range of each other.

 

Great piece of advice, but remember, we're in the UK and we have access to 13 channels. So channels 1, 7 and 13 are also non-overlapping!!!

 

 

 

Another way to look at it is this - if you have a single a/b/g AP, you effectively get 54Mbps speed shared between all the devices connected. So, if you have 10 devices you end up with 5.4Mbps each, minus overheads etc... Not much.

 

Nearly. Yes the data rate is shared, but the data throughput is roughly half of the available data rate. So you might be lucky to get about 2 Mbps.

 

Both Cisco and Trapeze recommend no more than 20 authenticated sessions/clients per ap, but each ap will support alot more unauthenticated sessions/clients.

 

Getting back on topic...

 

Are you using roaming profiles?

What are the users authenticating against? AD? NDS? Local Account?

Where is the authentication server? is it onsite or is it at a remote site?

How many authentication servers are you using?

Have you checked the logs on the servers & client laptops?

Do your AP's have the ability to adjust the transmit power?

When you got your survey done, did they check for interference?