Clean air -- how to interpret

[warner]

We are new to clean air. Having turned it on about a week ago, we're seeing less than perfection on some APs. The attachment shows two days of "minimum" readings for one of our 2.4 Gb/s radios. Others in the same building show similar "less than perfection" in the 2.4 Gb/s band. All the measurements in the 5 GHz band are 99 or 100. About half the APs in this building are 2600s.

My question is -- is this something that needs to be fixed, or is 95% clean good news? I don't know how to interpret the numbers and what should be judged "acceptable."  As a hedge against problems with the attachment here, the same picture is at

http://people.ucsc.edu/~warner/c8-2-air.png

Thank you.

[Rasika Nayanajith · Accepted solution]

Typically you would see this on 2.4GHz band as it is already congested. I would not bother unless it go down 60 or low (typically I would see overall 80% in my environment)

In this scale closer to 100 is always good. If you monitor this and you constantly see a lower value for particular area, check and see what other RF devices operate in that area.

HTH

Rasika

[warner]

Very useful. Thanks. Good to have a target.

I have been thinking about this some.

We are told that the SAGE chip looks for radio energy that does not begin with an 802.11 packet preamble. So, to first order, rogue APs will not get its attention. But if you have too many rogues within earshot and run the channel utilization up really high with too many beacon frames -- the result will be a lot of collisions. Too many of your own APs can help make this worse with co-channel interference, but rogues beacon at 1 MB/s and therefore take more air time. You can see this in CPI in a "utilization" report. If the utilization remains high when the users are asleep or gone, the air is full of beacons. A radio domain collision during a preamble will result in an event that gets kicked to the SAGE chip. So if the air is too busy, the SAGE chip will be unable to detect packet preambles and it will start attributing the noise to dirty air.