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Hi all,<BR>
<BR>
I noticed that some explanations about packet loss correlation has been added on the web site (<A HREF="http://linux-net.osdl.org/index.php/Netem).">http://linux-net.osdl.org/index.php/Netem</A>). But it seems that a mistakes has been made. Correct me if I'm wrong but wouldn't it be as follow:<BR>
<BR>
*Packet loss*<BR>
<BR>
Random packet loss is specified in the 'tc' command in percent. The smallest possible non-zero value is:<BR>
<BR>
\fig{<BR>
1/2^{32} = 0.0000000232%<BR>
}<BR>
<BR>
<TT># tc qdisc change dev eth0 root netem loss 0.1%</TT><BR>
<BR>
This causes 1/10th of a percent (i.e 1 out of 1000) packets to be randomly dropped.<BR>
<BR>
An optional correlation may also be added. This causes the random number generator to be less random and can be used to emulate packet burst losses.<BR>
<BR>
<TT># tc qdisc change dev eth0 root netem loss 0.3% 33.33%</TT><BR>
<BR>
This will cause 0.3% of packets to be lost, and each successive probability depends by about a third on the last one.<BR>
<BR>
\fig{<BR>
Prob_n = [Prob_{n-1} * 33.33/100] + [Rand() * (1-(<U><B>0.3</B></U>/100))]<BR>
}<BR>
<BR>
The first term into brackets representing the correlation between two successive packets and the second one representing the effective packet loss probability on one packet.<BR>
<BR>
Once again, tell me if I'm wrong. Thanking you in advance :<BR>
<BR>
H<BR>
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<PRE>
--
Hugues Van Peteghem
PhD Student
Computer Science Institute
FUNDP - The University of Namur
Belgium
<A HREF="http://www.info.fundp.ac.be/~hvp/">http://www.info.fundp.ac.be/~hvp/</A>
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