High CPU when transfering files

Unanswered Question
Jun 1st, 2009
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Currently running Software pack 7.1.0-EA .

Noticed a wierd situation when a user transfered a large file form his wireless laptop to a wired PC on the same vlan (Vlan1). A call was also in progress at the same time and the audio quality immediately became poor with words being repeated and sounding choopy and eventually dropping the call altogether. Users who were doing anything data related saw a real slowdown in speed and unable to browse the network or internet at some points.

Took a little while to figure out what was going on, but eventually narrowed it down to the tranfer of a specifi file from a specific user. We were able to replicate this problem easily.

Here are the details:

  1. When transfering a 577MB ZIP file from a laptop on the Wireless LAN (Vlan1 WPA encryption) to a Wired PC on VLAN 1, the CPU on the UC520 spiked to 100% until the transfer finished. When the CPU spiked, IP phones had up to 5 second lag betweeen picking up handset and getting dial tone, 5 second lag between pressing a button and recieving a response, call quality completly going out the window and sometimes even unregistering the phone. (Terminal Montor showed the phones unregistering abnormally)
  2. When going wired Laptop to wired PC with the same file, the CPU never spiked at all and every thing remained normal.
  3. When going Wired PC to Wireless Laptop with the same file, the CPU spiked the same, exactly as in scenario 1.
  4. When trying the same file transfer scenario (Scenario 1) with a laptop that had a Wirelss B card to a Wired PC, the CPU only spiked to 40% and everything continued to function just fine.

Screen shot below?


Please advise.




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Marcos Hernandez Mon, 06/01/2009 - 20:51
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May I ask you to run the Wireless Setup Wizard in order to configure your embedded AP?. The wizard automatically pushes WMM QoS config to the UC500. It is designed to work with the SPA525G and guarantee voice quality over the wifi (which I realize you do not have), but it would be interesting for you to test with WMM enabled.

Let me know,

Marcos Hernandez
Technical Marketing Engineer
Cisco Systems, Inc.

jaydien1358 Fri, 06/05/2009 - 09:07
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Currently all of our IP phones are 7960 wired phones. The only devices that are wireless are laptops and for data purposes only. The QoS problems that we experienced were on phones that were hard wired.

Does this change your thought process at all, in terms of your troubleshooting?

Also, I would like to upgrade my UC from the Beta Program load that I have been on to a current release and re-test. I'd like to see if that has any bearing on this issue.



Marcos Hernandez Fri, 06/05/2009 - 09:12
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Yes, this changes my thought process, if there are no wireless phones whatsoever. What concerns me is the fact that the production IOS is the same we used during the beta, so I don't have high hopes that the upgrade will fix it. Nevertheless, and for support related reasons, you have to move up to the production bundle.

Can you please do that? We will take it from there. In the meantime I will ask one of our wireless tech leads to help us recreate this.



jaydien1358 Fri, 06/05/2009 - 18:50
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I am using just the internal AP in my UC. No wireless phones and all the wireless traffice is just data.



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