3850 Improve speed #2
Comments
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Thanks for the feedback. Does |
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As far as I know it's only affecting traffic destined to the switch itself. |
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TCP window size is ideally set to I can programmatically determine latency with a ping test, but link bandwidth is tricky. I can't infer line rate of attached interface. Will you run some tests and see what works well for your bandwidth and latency? |
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In the past, adjusting TCP windows size hasn't consistently worked. This is in the context of SCP transfers using Netmiko. Some related discussion here: I also recently did an upgrade of a couple of IOS-XE devices from 16.08.01 to 16.12.03 using Ansible's net_put and the TCP window size did not make a performance difference (IIRC). It was taking over 3 hours to transfer a 542MB file to the device.
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It would be interesting to get more data on some of these performance problems and workarounds as the default transfer speeds are crazy slow... |
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@ktbyers My testing on the cat3k series suggests the limit is the control plane CPU. Even plain FTP pegs the CPU at <500Kbps, only a marginal improvement over TFTP. I looked for a way to force a weaker (and therefore less CPU-intensive) cipher suite for SCP, but didn't turn up anything. |
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Hi, I just tested again with http:
I have another one running without adjusting the tcp window size and it's still going
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@edurguti I guess the broader question is--is there any pattern when we can expect changing the TCP window size will work versus when it won't (as it seems to work in some cases, but not in others)? And I don't really have a good explanation as to why except for some vague "maybe something platform or OS-version specific". Let me see if I can test on my ISR2 router(s) and see whether your exact change works there or not. |
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I never had it fail on 3850/3650, but on 2960x it does fail. |
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I took a few while transferring:
NASGH3850-10-121-CSWT02#show processes cpu
Core 0: CPU utilization for five seconds: 6%; one minute: 16%; five
minutes: 10%
Core 1: CPU utilization for five seconds: 0%; one minute: 7%; five minutes:
3%
Core 2: CPU utilization for five seconds: 1%; one minute: 4%; five minutes:
2%
Core 3: CPU utilization for five seconds: 1%; one minute: 2%; five minutes:
2%
Core 4: CPU utilization for five seconds: 0%; one minute: 3%; five minutes:
2%
Core 5: CPU utilization for five seconds: 0%; one minute: 1%; five minutes:
1%
…On Tue, Jun 16, 2020 at 5:56 PM Austin de Coup-Crank < ***@***.***> wrote:
@ktbyers <https://github.com/ktbyers> @edurguti
<https://github.com/edurguti> can either of you post the output of sh
proc cpu sort during the transfer?
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I have found out that when doing http transfer on 3850s (probably 3650s), it takes forever (denali and up) - mine takes almost 6hours.
Increasing tcp windows size, helps tremendously:
I would try a few window sizes, this is the maximum window size allowed (maybe try/expect and decrease it if there's an IO error - I tried it on a 2960X and it failed a few times, I'll need to do further testing)
Below is an example of the file transfer across the atlantic, only 291.601 seconds, before this it was 5+ hours.
-CSWT02#copy http://10.95.238.50/cat3k_caa-universalk9.16.08.01a.SPA.bin flash: Destination filename [cat3k_caa-universalk9.16.08.01a.SPA.bin]? Accessing http://10.95.238.50/cat3k_caa-universalk9.16.08.01a.SPA.bin... Loading http://10.95.238.50/cat3k_caa-universalk9.16.08.01a.SPA.bin !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 425928073 bytes copied in 291.601 secs (1460654 bytes/sec)The text was updated successfully, but these errors were encountered: