What to look for in the AP support info if client performance is subpar?

Summary

This article discusses how to analyze the AP support info for possible RF impact on client connectivity.

Question

What to look for in the AP support info if client performance is subpar?

Customer Environment

Wireless network involving Ruckus APs

Root Cause

Interference in the environment the AP is operating.

Troubleshooting Steps

Whenever there are ping drops or high latency observed on a client when trying to ping the AP it is connected to, then pull out the support file from the AP.

How to pull out support file :

ZD Managed:
AP support info file can be obtained by going to ZD GUI -> Monitor -> Access Points. Under 'Currently Managed APs'? on the right hand side you can see 'Action'? column. Under Action you can see green color icon, if you place mouse pointer over that icon it shows "System Info". Click on that icon and save it to your local drive

Standalone AP:
Login to AP UI-> Maintenance. Under Maintenance click on Support Info then choose "Save to Local Computer" as Transfer Method. Once you select "Save to Local Computer" click on supportinfo.txt and save it.

Once you have the AP support file, make a search for 'AthStats'. 
 
### Athstats Radio 0 ###    --> 2.4 Ghz radio
### Athstats Radio 1 ###    --> 5 Ghz radio
Under the corresponding radio section, there should be Histogram table listed as below:
Histogram of PHY errors per second (pcttime in each range)
   0  1-500 ..1K  ..2K  ..5K ..10K ..20K ..50K .100K  more
   0    43    30    11     3     5     6     0     0     0
 
Phy errors are signals on the radio that it cannot interpret, either noise or damaged transmissions. Phy errors up to 10K should be tolerable. Moderate to high percentage values above 10K should be concerning.

The other parameter you can alternatively check is for the phrase "STUCK BEACON"

66 beacon stuck(bstuck)

AP user.warn kernel: wifi1: 69371 : stuck beacon (missed 11) action=0, scanning 0, syncbeacon 0, sc_beacons 1

AP user.warn kernel: NF Channel 5600 Chain 0  measured latest ctl:-119 ext:-50  capped median ctl:-108 ext:-88

AP user.warn kernel: NF Channel 5600 Chain 1  measured latest ctl:-117 ext:-50  capped median ctl:-108 ext:-88

AP user.warn kernel: NF Channel 5600 Chain 2  measured latest ctl:0 ext:0  capped median ctl:-88 ext:-88

AP user.warn kernel: wifi1: 70693 : stuck beacon (missed 11) action=0, scanning 0, syncbeacon 0, sc_beacons 1

AP user.warn kernel: NF Channel 5600 Chain 0  measured latest ctl:-119 ext:-50  capped median ctl:-108 ext:-88

AP user.warn kernel: NF Channel 5600 Chain 1  measured latest ctl:-117 ext:-50  capped median ctl:-108 ext:-88

AP user.warn kernel: NF Channel 5600 Chain 2  measured latest ctl:0 ext:0  capped median ctl:-88 ext:-88

AP user.warn kernel: wifi1: 75282 : stuck beacon (missed 11) action=0, scanning 0, syncbeacon 0, sc_beacons 1

When there is a continuous interference around the AP then it will be unable to broadcast the beacons and will fail to broadcast the SSIDs and hence the "stuck beacon" logs.

Airtime Stats is another useful section

Airtime utilized (percent) since clearing delta stats (1 sec)
   Busy:  5    RX: 28    TX: 27    Total: 59 
Histograms of airtime (pcttime in each range) since clearing all stats
        0  0-10  ..20  ..30  ..40  ..50  ..60  ..70  ..80  ..90 ..100
busy:  21    79     0     0     0     0     0     0     0     0     0
rx:     0     0    40    40    10     4     3     2     0     0     0
tx:     0    72     8    17     2     0     0     0     0     0     0
tot:    0     0     6    44    17     5    13    13     1     0     0

They indicate time spent by the radio in receiving the data (which is RX), in transmitting the data (which is TX), and percentage time wasted due to non-WiFi signals (which is Busy) in the operating frequency band.

High RX percentage values above 30% indicate too much co-channel interference or a misbehaving client.
High Busy percentage values above 30% should also be concerning as well because this percentage takes out the time from servicing the clients.

You should also check signal to the clients from the AP. Poor signal can cause slowness not just for clients with poor RSSI but also to the clients with good signal since they have to wait longer for poor signal clients to finish their transmission. Client signal strength can be seen under RSSI columns. Below is one such example. Make sure, it exceeds 30.
 -- wlan0 --
ADDR                 AID VLAN CHAN RSSI IDLE 
e0:f8:47:4d:2b:47   1Y    1        11     50    0     

Resolution

1. Please try to find out if there are any WiFi or non-WiFi (Ex: microwave ovens, cordless phone, baby monitor) devices around the APs. If you find any devices then try to turn OFF or move them away from the APs and see if it makes any difference or not.
 
2. The other options are to manually configure this radio to channel 1, 6 or 11 ? let it run and see if the Phy errors are better. 
To change the channel, please visit the the ZD GUI-->Configure-->Access Point and click on the Edit button of the MAC address of the AP on which you need change the channel.

You can also consider using ChannelFly as it scans each allowed channel to achieve best possible performance.
 
3. The last option is to reposition the AP away from noise.
 

 

Article Number:
000001597

Updated:
January 19, 2015 07:40 AM (almost 5 years ago)

Tags:
Performance, Troubleshooting, ZoneDirector, ZoneFlex Indoor, ZoneFlex Outdoor

Votes:
3

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