Hi,
the packet scheduler is invoked by dummynet at every packet arrival
and then at multiple of 1/HZ intervals. If you use the default
kernel setting, HZ=100 so you have most times rounded to multiples
of 10ms. I have been running my kernels with HZ=1000 for the past
4-5 years so the resolution is much better -- 1ms, which is appropriate
for links up to a few megabits/s
I think the above should explain the results you see.
cheers
luigi
> Hello,
>
> I did some measurements using Dummynet. It was just to see how
> it works. Tests are made with 0,7MBit stream (each 429Bytes Packets),
> 5,10,15,25,50 and 75 MBit.
>
> I tried a delay of 10ms for the testing connection.
> The tests were done with a Smartbits6000 with the capability to
> record the difference between sending and receiving a packet.
> Each test had a 8192 packets.
>
>
> The result show a strange behaviour, depending on the data rate.
>
> _
> | | vs. /\
>
> 0.7MBit - 15MBit: diffuse, fairly hig variance from 9.5 - 10.3ms
>
> 25 MBit: between
>
> 50MBit - 75MBit: very sharp, extreme precise, delivers a nearly 10ms
>
> (variance not calculated yet ... to be done ..)
>
> I am now a bit confused. Is it a matter of scheduling?
> Maybe too much fairness for such tasks :)
>
> Or is it some kind of prediction in dummynet which favours
> high data rates. I think I've seen something like that for packet
> loss in dummynet.
>
>
> Any opionions appreciated. Maybe I did something wrong
> and forget to set some sysctl properly.
>
> with kind regards,
> Jochen Kaiser
> --
> Jochen Kaiser kind@IRCNET, phone +49 9131 85-28134
> Network Administration mailto:[EMAIL PROTECTED]
> Regionales Rechenzentrum Universitaet Erlangen-Nuernberg, Germany
> GPG public key: http://www.uni-erlangen.de/~unrza2/public_key.txt
>
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