Date: Sat, 31 Mar 2001 11:14:27 +0200 From: Jochen Kaiser <Jochen.Kaiser@rrze.uni-erlangen.de> To: FreeBSD-hackers@FreeBSD.ORG Cc: luigi@info.iet.unipi.it Subject: unexpected peaks in dummynet;scheduling oddity? Message-ID: <20010331111427.A3209@devil.rrze.uni-erlangen.de>
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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:jochen.kaiser@rrze.uni-erlangen.de
Regionales Rechenzentrum Universitaet Erlangen-Nuernberg, Germany
GPG public key: http://www.uni-erlangen.de/~unrza2/public_key.txt
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