Wireless does not load balance and Connection drops to 1Mbps at a certain time

Unanswered Question
May 27th, 2010

Hi,

We had wireless LAN setup and it seems that every afternoon, the connection notification on their laptop drops to 1Mbps and slowness on the network is experienced. how can I identify the cause of this drop connection speed?

Also when one of the APs went down, the other nearby APs does not cover for the AP that went down, is it not supposed to cover for the downed AP?

BTW out setup is LAP with 4400 series WLC with VoWLAN running on it but on differed radio and SSID. Data is on b/g while VoWLAN is on A.

I have this problem too.
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George Stefanick Fri, 05/28/2010 - 16:15

Load balence doesnt work and its no fault of the WLC. The AP will send a reason code of 17 to the client telling the client to "go away". Some clients will ignore it will other will honor it...

Start a ping and tell me if the PHY goes up ...

Leo Laohoo Fri, 05/28/2010 - 18:05

Also when one of the APs went down, the other nearby APs does not cover for the AP that went down, is it not supposed to cover for the downed AP?

If you have more than enough APs in a space the WLC will say "I'm going to turn down the radios because alot of you are sooooooo close to each other".  This is good foresight.  When an AP fails and coverage hole is detected, the WLC can crank up the radios to compensate.  By the way, is Coverage Hole detection enabled?

We had wireless LAN setup and it seems that every afternoon, the connection notification on their laptop drops to 1Mbps and slowness on the network is experienced. how can I identify the cause of this drop connection speed?

Sounds like a pattern here, if you ask me.  The WLC can't do that.  You'll have to do it manually to find out what causes your wireless to slow down.  What exact time does this happen?  Is it caused by wireless interferences like other Rogue APs (etc), microwave ovens, electric motors, bluetooth, a sudden surge of wireless use to ONE specific AP?
ejlbarcelon Mon, 05/31/2010 - 18:49

yes coverage hole detection is enabled. also i am seeing a lot of coverage hole detection on the logs.

is there any problems with the coverage of the APs? should I place additional APs to cover up the holes?


as for the droping  to 1Mbps, this happens around 1pm- 2pm and last for up to 4 hours. if it is cause by rouge AP how can i prevent it. or can you recommed any steps on how can i trace sudden  surge of wireless use? i think this is not caused by microwave and bluetooth interference since the whole WLAN experience this slowdown.

Leo Laohoo Mon, 05/31/2010 - 19:02

also i am seeing a lot of coverage hole detection on the logs.

is there any problems with the coverage of the APs? should I place additional APs to cover up the holes?

If you have available funds/resources then putting additional APs won't hurt ... especially if one of the APs fail.  Putting additional APs will also help distribute the clients.

if it is cause by rouge AP how can i prevent it.

First, you have to know what radios is the AP using.  For example, if the Rogue AP is using 802.11b then disable your 802.11b or use a different channel.  I'm curious to know this is the case since the WLC would've used a different channel if a Rogue AP is broadcasting on similar channel (unless there's just too many Rogue APs using 802.11b).

you recommed any steps on how can i trace sudden  surge of wireless use

I'd like to identify/isolate how correct is my hypothesis that it's due to the sudden surge of wireless use.  If this is the case, then I'd also like to know what application(s) are being used to overwhelm the wireless.
ejlbarcelon Mon, 05/31/2010 - 20:43

Hi Leo,

Thanks for the help so far

I will try to add addtional APs. mind if I ask if there are any other causes of coverage holes?

If there is an application that overwhelm the wireless, will it affect the whole WLAN?

Leo Laohoo Mon, 05/31/2010 - 20:57

there are any other causes of coverage holes

Failure of an AP is one.  Change in the physical infrastructure like a sudden installation of compactors, for instance, which can cause a wireless signal to bounce back to where it came from because of the metal frame of the compactors acts as a reflector.

If there is an application that overwhelm the wireless, will it affect the whole WLAN?

Aside from applications, bluetooth, microwave ovens, 2.4Ghz wireless phones are a few things.  There are poorly written applications that can cause issues to wired/wireless.  There are also some devices that don't like wireless even though it's touted as a wireless device.

I will try to add addtional APs

Unless you determine what's causing this slowness, there's 50-50 chance that adding addtional AP will alleviate the issue.

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