topic disconnects and latency in ZoneDirector

disconnects and latency

randall_cohen — Fri, 19 Jun 2015 16:27:04 GMT

I'm getting short disconnects or maybe traffic issues. The most notable symptom is a hesitation in an RDP (Term Serv) session. It's long enough for the user to notice and miss a keystroke or mouse click, but too short for the session to fail. This happens in multiple locations, multiple APs, from multiple laptops and thin clients.

A quick continuous ping test to the device shows the latency jumping from 1ms to 1500ms for one ping every miniute, and keeps repeting. This may be nothing.

I'm also seeing a couple entries on the syslog that I'd really like to know what is causing them.
" Jun 19 06:51:53 AP-09 user.info kernel: >>>>>> ar5416GetNf: Failed to read CCA reg"
Call this AP-1 and it repetes every 8 minutes.

On another AP, we'll call it AP-2
"Jun 18 12:44:01 AP-07 daemon.warn Eved: STA-DISASSOC-REASON,nimac=78:4b:87:6f:73:94,func=ieee80211_send_mgmt,line=3700,hint=send station disassociate,rx_rssi=41,ack_rssi=0,reason=0,freq=2462,chan=11,stats=(67,4482,73,5464)"
"Jun 18 12:44:07 AP-07 user.notice root: APMGR-Out-Of-Run-State: ------ Sole Run debug info - Start -----"
Followed by debug and restart information. This repetes but not often and I don't a specific pattern, at least not yet.

If anyone has any ideas I'd really appreciate the help.

The problem may have been around for a long time. I've gone over the config way too many times and had an outside Ruckus partner look it over, so I don't think its a config issue. This is also across 2 firmware version, currently at 9.7.0.0.220 and I don't want to update because of the changes to WPA.

Thanks

Re: disconnects and latency

michael_brado — Mon, 22 Jun 2015 22:17:27 GMT

Hi Randall,

Interference is generally responsible for intermittent problems. Failed to read CCA reg is one message that is symptomatic.

https://support.ruckuswireless.com/answers/000003320

The more detailed definition of CCA:

Clear Channel Assessment (CCA) is one of two carrier sense mechanisms in WLAN (or WiFi). It is defined in the IEEE 802.11-2007 standards as part of the Physical Medium Dependant (PMD) and Physical Layer Convergence Protocol (PLCP) layer. CCA involves two related functions - CCA-CS and CCA-ED.

Carrier Sense (CCA-CS): Ability of the receiver to detect and decode a WiFi preamble. From the PLCP header field, the time duration (in us) for which the medium will be occupied can be inferred and when such WiFi preamble is detected the CCA flag is held busy until the end of data transmission.

Energy Detect (CCA-ED): Ability of the receiver to detect non-WiFi energy in the operating channel and back off data transmission. The ED threshold is typically defined to be 20dB above the minimum Rx sensitivity of the PHY. If the in-band signal energy crosses this threshold, CCA is held busy until the medium energy is below the threshold.

Your other AP message is a "clean-up" disassociate sent after a client roams away from an AP and is perfectly normal/ok.

I can think of one bug in 9.7.0.0.220 related to 'host only, loop detect' which could result in blips or occasional missed RDP keystrokes. It might be worth evaluating performance on 9.8.2.0.15.

Re: disconnects and latency

randall_cohen — Tue, 23 Jun 2015 11:10:54 GMT

Michael,
Thanks for the information, I was starting to think the problem was unrelated to the ping and CCA. I still think its interesting that I see this error on one AP but not on an adjacent AP, even when the same client was connected to the first and the next day the second. Regardless, it looks like I can ignore the ping and CCA issues.

For a very brief time I was at 9.8, just long enough to see all my bar code scanners not connect because of the change in WPA. I heard that there is a work around, configuring WPA in the CLI, for 9.8 but I'm still concerned about moving to this. I don't have a spare Zone Controller and dirupting the wireless devices right now would not be a good idea.

Can you point me to some documentation on this bug? How far back does it go?

Thanks

Re: disconnects and latency

michael_brado — Thu, 25 Jun 2015 23:08:54 GMT

Randall, the 9.8.3 Maintenance Release is not far off.

Meanwhile, although we recommend using a WPA2/AES combination, can you try WPA-Mixed/Auto that will allow any combination of WPA1 or WPA2 client who can use AES or needs to use TKIP?

Re: disconnects and latency

randall_cohen — Fri, 26 Jun 2015 11:15:38 GMT

I upgraded to 9.8 and lost connection to my bar-code scanners. I can't shut down the business like that again. That time I had to downgrade because no one could tell be why it append and it was set to auto. Later I was told that to support the older WPA/TKIP I would have to enable it on the SSIDs via the command line. Sorry but I can't take the chance just because it MIGHT resolve the problem. If there is a 9.8 that won't break my system AND resolves my problem as a known issue, then I can upgrade. But doing it just because isn't really a solution.

Re: disconnects and latency

michael_brado — Fri, 26 Jun 2015 16:54:17 GMT

Hi Randall,

Assuming you use a PSK method on your scanners, you don't need to use the CLI to reconfigure WLAN options.
From your ZD WebUI, Configure/WLANs page, Edit your present WLAN used by scanner clients. We *typically*
suggest a PSK authentication using WPA2 Method, and AES Algorithm. However, to try and troubleshoot your issues
after upgrade, you can try changing these to WPA-Mixed Method, with Auto (TKIP) Algorithm. Here are screen shots.

Re: disconnects and latency

randall_cohen — Fri, 26 Jun 2015 17:16:47 GMT

You're missing a very important point. This is not a theoretical discussion of what happens if I upgrade to 9.8. I DID upgrade and it wouldn't work and I opened a case with Ruckus which was escalated to "engineering". While waiting for their response I downgraded so my system would be usable. When they got back to me they said I could enable the WPA/TKIP for each SSID via the command line. I didn't try upgrading AGAIN to 9.8 and making the CLI change because I can't afford to take the scanners off-line again.

As for what is RECOMMENDED, it's irrelevant since my scanners do not support WPA2

Now if there is some kind of document fix for the problem in 9.8 that's different story. Send me a link to the information and I'll see what can be done.

Re: disconnects and latency

michael_brado — Fri, 26 Jun 2015 18:42:32 GMT

The real question is what type of authentication does your (mfgr?) scanner have configured?

Re: disconnects and latency

randall_cohen — Fri, 26 Jun 2015 18:52:34 GMT

encryp is WPA/TKIP auth is none.
And until we role-out new ones that's the way its going to stay. Ya I know..

Re: disconnects and latency

michael_brado — Fri, 26 Jun 2015 21:47:25 GMT

Hi Randall,

We have a couple knowledge base articles related to working with barcode
readers and handheld scanners. I have a feeling your scanners might only
support 802.11b/g too, if they don't have WPA2. I'm glad they work on your
previous version, and that you have a backup configuration on that release
when you rolled back.

If you have a dedicated WLAN for scanners is helpful, so you can apply
changes just to that WLAN, but it might take some testing after upgrading to
9.8 again (weekend?) to test Let me give you these.

KBA-3278: How to enable TKIP on ZD 9.8+
https://support.ruckuswireless.com/answers/000003278

This may be the article you were referred to before, providing CLI commands after the suggestions I offered. It does require an SSH login to your ZD to run the CLI command under config mode, and will override WebUI settings in the future, but will setup WPA1/TKIP, that should be compatible with your age scanner product.

I want to add the WLAN config command "no ofdm-only" to insure 802.11b only
clients should be able to connect. I tested the command syntax on my ZD.

ruckus# config
You have all rights in this mode.
ruckus(config)# wlan ScannerSSID
The WLAN service 'ScannerSSID' has been loaded. To save the WLAN service, type 'end' or 'exit'.
ruckus(config-wlan)# no ofdm-only
The mgmt-tx-rate will be set to the same value as bss-minrate due to ofdm-only change.
The command was executed successfully. To save the changes, type 'end' or 'exit'.
ruckus(config-wlan)#
ruckus(config-wlan)# open wpa passphrase 1234567890 algorithm TKIP
The command was executed successfully. To save the changes, type 'end' or 'exit'.
ruckus(config-wlan)#
ruckus(config-wlan)# exit
The WLAN service 'ScannerSSID' has been updated and saved.
Your changes have been saved.
ruckus(config)# exit
Your changes have been saved.
ruckus#

KBA-1765: Barcode readers and Handheld scanner issue
https://support.ruckuswireless.com/answers/000001765

Has a .pdf with advice on alternative test with an Open Auth test (would require changing a scanner) if the WPA/TKIP only configuration didn't work.

If a scanner can connect to Open Auth, can it connect if you hide the SSID?
Yes or no, if you need to use Open for the scanners, you can apply an L2
MAC filter ACL, to only allow scanner connections, as a possible alternative?

Forum community members may have some inputs too, otherwise I hope
this is helpful.

(if the last article doesn't appear yet, I just did an edit, so it might be a few min)

Re: disconnects and latency

ziv_l — Sun, 28 Jun 2015 08:37:28 GMT

Hello
I`v experienced similar problems and found out an unsynchronized link bwtenn BB switch and the main router. on one hand the ethernet port showd 100 HD and on the adjacent port 100 FD. Try and check all your link syncronization.
Ziv