mirror of
https://git.proxmox.com/git/mirror_iproute2
synced 2025-10-09 22:23:13 +00:00
150 lines
4.9 KiB
Groff
150 lines
4.9 KiB
Groff
.TH NETEM 8 "25 November 2011" "iproute2" "Linux"
|
|
.SH NAME
|
|
NetEm \- Network Emulator
|
|
.SH SYNOPSIS
|
|
.B "tc qdisc ... dev"
|
|
.IR dev " ] "
|
|
.BR "add netem"
|
|
.I OPTIONS
|
|
|
|
.IR OPTIONS " := [ " LIMIT " ] [ " DELAY " ] [ " LOSS \
|
|
" ] [ " CORRUPT " ] [ " DUPLICATION " ] [ " REORDERING " ]"
|
|
|
|
.IR LIMIT " := "
|
|
.B limit
|
|
.I packets
|
|
|
|
.IR DELAY " := "
|
|
.BI delay
|
|
.IR TIME " [ " JITTER " [ " CORRELATION " ]]]"
|
|
.br
|
|
[
|
|
.BR distribution " { "uniform " | " normal " | " pareto " | " paretonormal " } ]"
|
|
|
|
.IR LOSS " := "
|
|
.BR loss " { "
|
|
.BI random
|
|
.IR PERCENT " [ " CORRELATION " ] |"
|
|
.br
|
|
.RB " " state
|
|
.IR p13 " [ " p31 " [ " p32 " [ " p23 " [ " p14 "]]]] |"
|
|
.br
|
|
.RB " " gemodel
|
|
.IR p " [ " r " [ " 1-h " [ " 1-k " ]]]"
|
|
.BR " }"
|
|
|
|
.IR CORRUPT " := "
|
|
.B corrupt
|
|
.IR PERCENT " [ " CORRELATION " ]]"
|
|
|
|
.IR DUPLICATION " := "
|
|
.B duplicate
|
|
.IR PERCENT " [ " CORRELATION " ]]"
|
|
|
|
.IR REODERING " := "
|
|
.B reorder
|
|
.IR PERCENT " [ " CORRELATION " ] [ "
|
|
.B gap
|
|
.IR DISTANCE " ]"
|
|
|
|
.SH DESCRIPTION
|
|
NetEm is an enhancement of the Linux traffic control facilities
|
|
that allow to add delay, packet loss, duplication and more other
|
|
characteristics to packets outgoing from a selected network
|
|
interface. NetEm is build using the existing Quality Of Service (QOS)
|
|
and Differentiated Services (diffserv) facilities in the Linux
|
|
kernel.
|
|
|
|
.SH netem OPTIONS
|
|
netem has the following options:
|
|
|
|
.SS limit packets
|
|
|
|
limits the effect of selected options to the indicated number of next packets.
|
|
|
|
.SS delay
|
|
adds the chosen delay to the packets outgoing to chosen network interface. The
|
|
optional parameters allows to introduce a delay variation and a correlation.
|
|
Delay and jitter values are expressed in ms while correlation is percentage.
|
|
|
|
.SS distribution
|
|
allow the choose the delay distribution. If not specified, the default
|
|
distribution is normal. Additional parameters allow to consider situations in
|
|
which network has variable delays depending on traffic flows concurring on the
|
|
same path, that causes severeal delay peaks and a tail.
|
|
|
|
.SS loss random
|
|
adds an independent loss probability to the packets outgoing from the chosen
|
|
network interface. It is also possibile to add a correlation, but this option
|
|
is now deprecated due to the noticed bad behaviour.
|
|
|
|
.SS loss state
|
|
adds packet losses according to the 4-state Markov using the transition
|
|
probabilities as input parameters. The parameters p13 is mandatory and if used
|
|
alone corresponds to the Bernoulli model. The optional parameters allows to
|
|
extend the model to 2-state (p31), 3-state (p23 and p32) and 4-state (p14).
|
|
State 1 corresponds to good reception, State 4 to independent losses, State 3
|
|
to burst losses and State 2 to good reception within a burst.
|
|
|
|
.SS loss gemodel
|
|
adds packet losses according to the Gilbert-Elliot loss model or its special
|
|
cases (Gilbert, Simple Gilbert and Bernoulli). To use the Bernoulli model, the
|
|
only needed parameter is p while the the others will be set to the default
|
|
values r=1-p, 1-h=1 and 1-k=0. The parameters needed for the Simple Gilbert
|
|
model are two (p and r), while three parameters (p, r, 1-h) are needed for the
|
|
Gilbert model and four (p, r, 1-h and 1-k) are needed for the Gilbert-Elliot
|
|
model. As known, p and r are the transition probabilities between the bad and
|
|
the good states, 1-h is the loss probability in the bad state and 1-k is the
|
|
loss probability in the good state.
|
|
|
|
.SS corrupt
|
|
allows the emulate the random noise introducing an error in a random position
|
|
for a chosen percent of packets. It is also possible to add a correlation
|
|
through the proper parameter.
|
|
|
|
.SS duplicate
|
|
using this option the chosen percent of packets is duplicated before queueing
|
|
them. It is also possible to add a correlation through the proper parameter.
|
|
|
|
.SS reorder
|
|
there are two ways to use this option:
|
|
|
|
.B "reorder gap"
|
|
.I 5 10
|
|
.br
|
|
in this first example every 5th (10th, 15th) packet is sent immediately while
|
|
other packets are delayed by 10 ms
|
|
|
|
.B reorder
|
|
.I 25% 50%
|
|
.br
|
|
in this second example 25% of packets are sent immediately (with correlation of
|
|
50%) while the other are delayed by 10 ms.
|
|
|
|
.SH LIMITATIONS
|
|
The main known limitation of Netem are related to timer granularity, since
|
|
Linux is not a real-time operating system.
|
|
|
|
.SH SOURCES
|
|
.IP " 1. " 4
|
|
Hemminger S. , "Network Emulation with NetEm", Open Source Development Lab,
|
|
April 2005
|
|
(http://devresources.linux-foundation.org/shemminger/netem/LCA2005_paper.pdf)
|
|
|
|
.IP " 2. " 4
|
|
Netem page from Linux foundation, (http://www.linuxfoundation.org/en/Net:Netem)
|
|
|
|
.IP " 3. " 4
|
|
Salsano S., Ludovici F., Ordine A., "Definition of a general and intuitive loss
|
|
model for packet networks and its implementation in the Netem module in the
|
|
Linux kernel", available at http://netgroup.uniroma2.it/NetemCLG
|
|
|
|
.SH SEE ALSO
|
|
.BR tc (8),
|
|
.BR tc-tbf (8)
|
|
|
|
.SH AUTHOR
|
|
Netem was written by Stephen Hemminger at Linux foundation and is based on NISTnet.
|
|
This manpage was created by Fabio Ludovici <fabio.ludovici at yahoo dot it> and
|
|
Hagen Paul Pfeifer <hagen@jauu.net>
|