netdev - Netem Delay Normal Distribution

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 26 Oct 2013 21:31:03 -0500
From:	anirup dutta <adutta2@...edu>
To:	netdev@...r.kernel.org
Subject: Netem Delay Normal Distribution

Hello,

I try this on my device

sudo tc qdisc del dev eth0 root netem delay 100ms 20ms distribution normal

I use iperf for transmitting UDP packets and I modified its code to
get per packet delay. When I plot the distribution of delays and
analyze the delays they pass the normality tests.

The only problem that I am not able to understand is that the mean of
those delays shift to 125ms. Its not only me. There was another study
and it observed the same thing.

http://www.researchgate.net/publication/224256550_An_Empirical_Study_of_NetEm_Network_Emulation_Functionalities/file/d912f5058c9b1e409b.pdf

Figure 7

I found out that this command is valid

sudo tc qdisc del dev eth0 root netem delay 1ms 20ms distribution normal

So I have a feeling that mean gets shifted from the base delay to
avoid negative delay values.

It would be great if someone can confirm how it is implemented?

Regards,

Anirup
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html