ArubaOS and Controllers

Reply
Occasional Contributor II
Posts: 36
Registered: ‎04-03-2007

ARM Channel changing

I recently upgraded to Airwave 7.2.0...One of the features is to see when an AP changes it channel...My question is how often should ARM change channels?
I have a Dorm that has around a 100 AP65's.. I noticed the Noise level is at -98
and the 2.4GHz channels on some of the AP's have changed 5 to 7 times over a 12 hour period....I am seeing this in other building as well. We have around 2200 AP's. Could ARM be to aggressive? Code version 3.4.2.6
Brian
Guru Elite
Posts: 21,280
Registered: ‎03-29-2007

Re: ARM Channel changing

Adaptive Radio Management (ARM) is an algorithm that chooses the power and channel of an access point based on the environment. ARM has a number of timers that determine thresholds as well as how soon to make a change once it detects it needs to. By default these timers are good for most users.

A what would not be good is if ARM changes channels too much and causes client disconnects. ARM client-aware is a parameter that can be enabled so that the access points will not change channel while clients are attached. It is located in the ARM profile of the AP-Group.

A nose level of -98 is very good and means that there is little if any non-802.11 forms of interference. This is only one parameter that ARM uses to determine how often to change channel or power.

Please view the article here: http://kb.arubanetworks.com/cgi-bin/arubanetworks.cfg/php/enduser/std_adp.php?p_faqid=927 to see some information about ARM. If you also search the knowledgebase for ARM, you will also find more articles, that speak more on ARM.

Long story short, there is no right answer about how many times an access point should change channels or power. If you feel this is an issue, please contact TAC so they can look at your setup and determine if something needs to be tweaked. The main issue is if your clients are having problems connecting and passing traffic.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Occasional Contributor II
Posts: 36
Registered: ‎04-03-2007

RX Sensitivity Tuning Based Channel Reuse

Colin,
Thank you for the quick reply....I was thinking of turning on RX Sensitivity Tuning Based Channel Reuse (Currently disabled) The area that I am seeing this issue have a pretty dense deployment...What option would you choose if I were to turn it on
Static or Dynamic?
Brian
Guru Elite
Posts: 21,280
Registered: ‎03-29-2007

Re: ARM Channel changing

That knob is only used for non-802.11 interference. You can turn on Arm Mode Aware on the 2.4ghz band if you think you have too many access points on in the Area. Please read this knowledgebase article here: http://kb.arubanetworks.com/cgi-bin/arubanetworks.cfg/php/enduser/std_adp.php?p_faqid=375 before you do, however.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Regular Contributor I
Posts: 241
Registered: ‎04-03-2007

Re: ARM Channel changing

IN this thread Colin mentioned that "A nose level of -98 is very good and means that there is little if any non-802.11 forms of interference".

Where in Airwave are you getting the noise levels? Is this the SNR value or just the "noise" value? Are "lower" values better? For example, is -98 better than -40?

We're seeing frequent channel changes in our AP-dense res halls and I think I'm a little confused about the terminology.

Thanks,
Mike
Moderator
Posts: 123
Registered: ‎04-17-2009

Re: ARM Channel changing

AirWave 7.2 keeps noise floor information over time and displays it in a graph on the radio statistics page. To get to the page go to the AP-->Monitoring page for a specific AP and then click on the statistics link in the interfaces section.

This noise value is the noise floor from the controller. Lower is better. Anything below -90 is great.

In general channel changes by ARM are not a bad thing. ARM has a few different behaviors. Channels will change more frequently if there are no users associated to the AP. When there are no users associated the AP will freely change channel to where the least interference is. If users are associated, ARM will only change channels if there are a large number of errors or a ton of interference. The user experience needs to already be impacted and pretty bad for ARM to make a change with a user associated.

Can you try going to the statistics page and looking at the connected users graph and the channel change graphs at the same time? My guess is that you had no users on that 2.4 ghz radio when it was optimizing channel.
Guru Elite
Posts: 21,280
Registered: ‎03-29-2007

Re: ARM Channel changing

Michael,

I was referring to the noise value. I also overgeneralized in my answer, so forget what I said about interference. -98 is MUCH better than -40. You want it to be -85 to -100 or more if possible.

You would find that noise parameter on each channel that the access point is scanning on the commandline by typing "show arm rf-summary ap-name ". In the latest version of Airwave (7.2.0) you can see this by clicking on the "Statistics" parameter for each access point.


This is different from the SNR or the Signal to Noise ratio, which generally represents how well the access point can hear the client (very generally). That number should be 20 and above for decent client connectivity.

There are a number of things that can bring about more frequent channel changes and you should contact support for their opinion on that, because each environment is individual.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Regular Contributor I
Posts: 241
Registered: ‎04-03-2007

Re: ARM Channel changing

Thanks all this is very helpful. We are currently running Airwave 7.1.3. I was told that 7.2.1 will be announced next week and plan to upgrade then.

We're currently running ArubaOS 3.4.3.0. Will these AP statistic enhancements in Airwave be able to work with this version of ArubaOS?

Thanks,
Mike
Search Airheads
Showing results for 
Search instead for 
Did you mean: