Clients getting inconsistent pings

[Patrick McHenry]

Has anybody seen this kind of performance from their clients. See attached. Whether  they are on b,g, or a it seems we get the same performance from these clients and they are dropping their connections. thanks.

Also, is this normal:

Controller Associated Latency 0 d, 00 h 01 m 11 s

The others are:

Controller Associated Latency 0 d, 00 h 00 m 55 s

Sorry for the repost.

Pat

[Nicolas Darchis]

Hi,

that output is the time the AP took to associate to the WLC and is not relevant in your case.

Your ping test is totally not a reliable test. Wireless clients tend to have a "sleep mode" which means they sleep a lot so they don't reply to pings immediately. If you ping a client which is doing a huge FTP transfer you should see faster response time (sleeping less).

About client disconnection, this could be insufficient RF coverage or any other issue that you can troubleshoot by collecting a "debug client " and waiting for a disconnection to happen.

Hope this helps.

Nicolas

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[Patrick McHenry]

So when a client is in the process of sending/receiving traffic, it is more likely to have better ping responses? These pings are really so though. Do the clients sleep between the pings?

[Nicolas Darchis]

It more or less (I'm simplying but that's the spirit) goes like this :

Sending traffic

sleeping immediately

waking up because we have some more traffic to send

first checking with the AP if there is buffered traffic

sending the traffic the client has to send

sleeping again

a client doesn't eternally sleep, so even if it has no traffic to send it wakes up every 100 or 200 msec to check for buffered traffic.

This is why, if the client has a huge transfer ongoing, he's more likely to be awake more constantly.

You can configure the client wireless adapter to be constantly awake on some drivers as well.

There are various variations like UAPSD with WMM where the client automatically receives its buffer traffic when he sends traffic, but basically the spirit is that the client sleeps any time where he's doing nothing. And when we say sleep mode, it's just the wireless adapter going silent and not listening. It usually doesn't last longer than 100-200msec and can last for few msecs only too.

If you go with barcode scanners or really more "industrial" and "trying to save as much battery as possible" devices, they can sleep for several seconds.

Nicolas.

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[Patrick McHenry]

Thanks for the help.

We have found that the pings are getting better. We updated the windows wifi card so when you change the pwer management on the client setting to max(all the way to the right) and unchecked the default box it stays after reboot.  Would the power managment setting on the client have anything to do with the ping responses and or the drops we were experiencing. By the way, the clients are at a remote site, accessing an app at our main site and I've been assured that they were not only dropping from the app but, dropping from the wifi.

[Nicolas Darchis]

As previously mentioned, I think that part has no relation with the power save we just discussed.

See the end of my first message :

About client disconnection, this could be insufficient RF coverage or any other issue that you can troubleshoot by collecting a "debug client " and waiting for a disconnection to happen

Nicolas

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[Patrick McHenry]

Thanks,Man.