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I can't seem to figure out what's wrong with my iPerf executable. I am trying to automate the execution of iPerf using a Telnet script (this is the one I am using https://github.com/ngharo/Random-PHP-Classes/blob/master/Telnet.class.php). I'd like to know what I can do to find the reason for the bottleneck, assuming the PHP script works as expected. Basically, if I run it manually over the command line, I get the rates desired however if I run it remotely using the script I get capped performance.

What I have tried is using tcpdump to output the logs while iperf is running and then reading it using Wireshark. All I can observe is that the time differences between the fragments are larger when using the script, which means the rates will be lower. I don't know what to do next after this. Any ideas what else I can look at/try? I've tried changing kernel values for buffer sizes using sysctl but this has no effect as running it manually always works anyway.

Note that I have tried to play around with all the iperf configuration options such as -w, -l, -b (I havent tried burst mode). No success.

user21961
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  • Compare the environment variables between the command line and remote cases. – Seth Noble Jan 12 '16 at 18:42
  • @SethNoble Seems like the iperf server slows down for some reason when done in the automated case. It just runs slower and cannot keep up with the packets coming in. – user21961 Jan 13 '16 at 20:04
  • Understood: check the environment variables of the automated and interactive environments. There may be some difference, perhaps not an obvious one, which changes the behavior of iperf. – Seth Noble Jan 13 '16 at 20:06

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