M and MSM Series

MSM422, connectivity problems and Rx FCS errors

Frequent Advisor

MSM422, connectivity problems and Rx FCS errors


I'm absolutely cluseless and couldn't find any infos here about the following.
Any help would be greatly appreciated! This is driving me nuts.
Thank you very much in advance.

I'm currently testing an MSM422 with only one client connected.
The room where this notebook is located isn't extremely well covered by the accesspoint, but the snr is still between 23-30. Signal is about -69 to -72db, noise -95 to -98db.

Radio is set to 5Ghz pure N (no legacy clients around).

My problem is intermittent connectivity issues: when I ping this notebook with default settings, delays are between 3-5ms and sometimes for a few packets in between they reach ~ 900ms.

I checked the status/wireless page and saw that the values for single/multiple retry frames are quite high, but what worries me most is that "Rx FCS errors" increase by 1 per second when I just ping the notebook.

On the other hand a floog ping (ping -f from a linux box) to a client connected via an MSM410 with snr about 36, resulted in only ~ 30 Rx FCS Errors after >18000 packets.

What exactly do these Rx FCS Errors in conjunction with a wireless radio mean and how much is considered normal? Is this something to expect with an snr of only 23-30 and signal -70?

The client is an intel wifilink 5300 with latest drivers, no powersave, maximum transmit power.

And my last problem: single retry frames: when I do a flood ping, they increase by ~ 300 every 5 seconds.

Does anyone know what I could do, what the reason might be and where I should start troubleshooting? Maybe someone could point me into the right direction.

Thank you very much!

Frequent Advisor

Re: MSM422, connectivity problems and Rx FCS errors

I think it's strange, that when I ping with a packet size of 1428 and an interval of 5 packets per second, those errors don't increase any faster.. it behaves exactly the same as if I just ping using default size of 84bytes.
Frequent Advisor

Re: MSM422, connectivity problems and Rx FCS errors

Really strange! I just noticed that another MSM422 with NO clients connected or around for the last two days had a very high Rx FCS errors value.

I cleared the statistics and watched this value increasing by about 1/second.. it's 2am here and there's no client activity.

A MSM410 located in the near distance on another channel, also configured for 5Ghz pure N, reports a Rx FCS Error value of 0!

Does anyone know what could be the reason for those errors and why they only increase for all our MSM422 but not MSM410?

Firmware is latest for all the units.

Thank you very much!
Matt Marcos
Occasional Advisor

Re: MSM422, connectivity problems and Rx FCS errors

Turn off Automatic Power control. I had similar issues to yourself. once this was off it all went away...
Frequent Advisor

Re: MSM422, connectivity problems and Rx FCS errors

Thanks for the suggestion, but the problem still exists.

I did some further testing with different notebooks and extremely good signal strength:

Local websites for example the APs webinterface *sometimes* get stuck loading for about 10 seconds (refreshing the site ~ 20 times = 1 hang), despite excellent snr (>40, signal ~ -50, noise ~ -95).

ping delays are inconsistent: between 3-8ms.
same host with an old 802.11g AP, connected to the same switch: <1ms

This all happens with pure N (5Ghz), N/a, a, short or long guard interval, different rts treshold settings I tried, different channels -though site surveys have shown that there's nothing else on that channels, there's even no other AP in the whole 5GHz band, different notebooks (but all use intel cards, namely 5100 and 5300, all latest drivers directly from intel's website + any power savings turned off (psp -> cam, et.c.))

Still, single retry frames count upwards at a rate of *at least* 1/second at night with only me connected (idle, except ping).

Firmware is latest (5.4.1)

All this also happens with a MSM410, same firmware.

I also moved them from a small cisco poe gigabit swith to hp power injectors + procurve 1810g-24 switches. Didn't change anything.

I'm really desperate now since these issues won't resolve despite trying for quite a long time and an upgrade from 5.4.0 to 5.4.1.

Of course it's too early to draw any conclusions, but I already regret buying those units.

Reading the release notes known issues:

"Under a very heavy wireless load, wireless client traffic can become very slow after
several large file transfers. Terminating and reassociating client stations does not
resolve the issue. The only solution is to restart the AP."

Even though my problems aren't related as I often rebooted the AP before testing (because of that known issue), this sounds really bad. I reboot the APs every night just to be a bit more save.

Does noone else have issues like that?
Frequent Advisor

Re: MSM422, connectivity problems and Rx FCS errors

Could all this be related to our intel cards?
Would another chipset be better to use with the MSM aps?

It's a big problem for us that even clients with superb signal quality experience intermittent very high delays (particularly noticeable when accessing local or remote websites.)

I'm sure this can't be the usual MSM AP experience.

Does anyone know what else I could try to improve this situation or to get rid of this problem?

And does anyone know more about FCS errors in conjunction with wireless networks and how much attention I should pay them?
Are those errors more critical than multiple/single retry frames?

Thank you very much for any help!
Frequent Advisor

Re: MSM422, connectivity problems and Rx FCS errors

After further monitoring, I thought it's best to create a new thread with better and more accurate description of the problem.
Henning Søilen

Re: MSM422, connectivity problems and Rx FCS errors

Well, I have the exact same problem. Also MSM422 and clents with intel 6300 and 6250 wireless cards. Would like to see a solution here.