disconnects and latency

[randall_cohen]

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

 

[michael_brado]

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.

[randall_cohen]

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

[michael_brado]

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?

[randall_cohen]

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.