Wireless Access

Hello,

We are a small school district with several schools.  At our HS we can have anywhere from 700-1000 devices on our IAP Clusters.  We had an vendor originally configure out devices but I'm finding that they likely didn't know what they were doing.  To combat the devices from "bogging down" a single AP they had enable Client Match, however for reading through forums I think they changed the default settings.  What we were finding was that Chromebooks, and likely other devices, were constantly moving to other AP's and in the process would briefly lose thier internet connection which affected things like testing and Khan Academy exercises.  For now I have disable client match to stop the complaints from piling up but there have been some speed complaints and that is likely because of large amounts of devices on a single AP.  Other surrounding AP's, at times, are under utilized so that makes me think Client Match would be good but just needs to be fine tuned.

On another not, when devices were switching AP's due to client match the delay was enough to pop up warnings in the tests/Khan that the user didn't have internet connection.  Would this be something that enabling Fast Roaming protocols could assist with or would that be too much overhead for the # of devices and our 43 AP cluster?

I have attached our RF configurations.  My hunch is we should turn down power and disable 80 MHz support but I'll wait for an experts input.  Thanks in advance for any advice anyone lends.

Yes.  Uncheck 80mhz channels and Wide channels (results in 20 mhz channels).  Clients will "stick" to 80mhz wide channels because clients have a higher association rate.  Best to make it 20mhz that has more channels, less cochannel interference.  What are your ARM Min and Max transmit power for the cluster?  You might have to end up turning down the power.  Start with the 20mhz wide channels first.  Leaving off clientmatch is fine, for now.

How much lower can I expect speeds to be with the narrow channels?  As far as power goes, the min is 3 and the max is max.  Let me know what your suggestion would be for that.  Thanks.

Shawn

It all depends.  Many clients or devices cannot support 80mhz channels.  In addition, having 80mhz channels causes alot of contention in high density areas, which decreases the speed.   Lastly, most people do not run faster than gigabit ethernet to their access points or between their switches, so the theoretical maximum could not be approached, anyways.

Please see the high density validated reference design guide here:  http://community.arubanetworks.com/t5/Validated-Reference-Design/High-Density-Wireless-Networks-for-Auditoriums/ta-p/155578 for more details.

Long story short, 80 mhz channels is not efficient and causes contention in a high density environment.  I would try backing off to 40mhz first. 

Your ARM  minimum and maximum should have a difference of at most 6 (12 min and 18 max, is a good start for example), so that it won't be possible to have access points with transmit power that vary much between each other.

I will work on making these adjustments after hours because I believe it requires a reboot of AP's.  

I do have other schools using the Client Match.  What are the default settings for CM calculating interval, neighbor matching %, CM threshold and SLB mode?  Should the defaults be left for a situation like mine?

Thanks for all your help. 

Those changes do not require a reboot.

Do not make any ClientMatch changes.

Please see the client match defaults here:  http://www.arubanetworks.com/techdocs/Instant_423_WebHelp/InstantWebHelp.htm#UG_files/ARM/Configuring_ARM-Features.htm#Spectrum

Thank you for all the information.  I have made the changes you suggested and will monitor the results.  

With Client Match enabled will there always be a brief disconnection by the device as it is "handed off" to another AP?  Is there a way to improve the disconnection time or eliminate it all together?

ClientMatch typically sends a deauth to the client.  Most clients will reconnect automatically.  Again, this is only for client where the AP thinks there is a much better AP that the client should be connecting to, or load balancing is involved.  If you get the transmit power of your access points right, there will be less or little need for Client Match.

More reading info  on Client Match is here:  http://community.arubanetworks.com/t5/forums/searchpage/tab/message?include_tkbs=true&location=category:Support-Documentation-Downloads&q=client%20match%20instant