| .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 " ]]]" |
| |
| .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> |