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In order to facilitiate some performance testing I am attempting to throttle the ip traffic on a particular machine - I want limit it to 1Mbit/sec.

I have a separate test machine where this command works just fine:

tc qdisc add dev eth0 root tbf rate 1mbit burst 5kb latency 70ms peakrate 1.001mbit minburst 1540

On the real box where I want to apply this, I get weirdness. The exact same command limits traffic to 6Kbit/sec. Any ideas why?

unanme -a shows

Linux IPERF1 2.6.18-128.el5PAE #1 SMP Wed Dec 17 12:02:33 EST 2008 i686 i686 i386 GNU/Linux

We have a three different ways of monitoring the throughput: The actual application we are testing which reports the throughput we see. We also some Tivoli monitoring on a switch and we have an HTTP client which downloads a file from an HTTP server on the box in question. All three methods show 6Kbs when the TBF is applied, and many Mbs when we remove the TBF.

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Timer resolution might influence your results, see here for example. What happens if you increase burst to 10kb and remove peakrate and minburst?

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Unfortunately I can't go back and check this. I'm pretty sure your idea is correct. – djna Oct 13 '10 at 20:34

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