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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 14:18:53 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 14:18:53 +0000 |
commit | a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67 (patch) | |
tree | 8feaf1a1932871b139b3b30be4c09c66489918be /man/man8/tc-netem.8 | |
parent | Initial commit. (diff) | |
download | iproute2-a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67.tar.xz iproute2-a0e0018c9a7ef5ce7f6d2c3ae16aecbbd16a8f67.zip |
Adding upstream version 6.1.0.upstream/6.1.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man/man8/tc-netem.8')
-rw-r--r-- | man/man8/tc-netem.8 | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/man/man8/tc-netem.8 b/man/man8/tc-netem.8 new file mode 100644 index 0000000..2177585 --- /dev/null +++ b/man/man8/tc-netem.8 @@ -0,0 +1,236 @@ +.TH NETEM 8 "25 November 2011" "iproute2" "Linux" +.SH NAME +NetEm \- Network Emulator +.SH SYNOPSIS +.B "tc qdisc ... dev" +.IR DEVICE " ] " +.BR "add netem" +.I OPTIONS + +.IR OPTIONS " := [ " LIMIT " ] [ " DELAY " ] [ " LOSS \ +" ] [ " CORRUPT " ] [ " DUPLICATION " ] [ " REORDERING " ] [ " RATE \ +" ] [ " SLOT " ]" + +.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 " ]]] } " +.RB " [ " ecn " ] " + +.IR CORRUPT " := " +.B corrupt +.IR PERCENT " [ " CORRELATION " ]]" + +.IR DUPLICATION " := " +.B duplicate +.IR PERCENT " [ " CORRELATION " ]]" + +.IR REORDERING " := " +.B reorder +.IR PERCENT " [ " CORRELATION " ] [ " +.B gap +.IR DISTANCE " ]" + +.IR RATE " := " +.B rate +.IR RATE " [ " PACKETOVERHEAD " [ " CELLSIZE " [ " CELLOVERHEAD " ]]]]" + +.IR SLOT " := " +.BR slot " { " +.IR MIN_DELAY " [ " MAX_DELAY " ] |" +.br +.RB " " distribution " { "uniform " | " normal " | " pareto " | " paretonormal " | " +.IR FILE " } " DELAY " " JITTER " } " +.br +.RB " [ " packets +.IR PACKETS " ] [ " +.BR bytes +.IR BYTES " ]" + + +.SH DESCRIPTION +NetEm is an enhancement of the Linux traffic control facilities +that allow one to add delay, packet loss, duplication and more other +characteristics to packets outgoing from a selected network +interface. NetEm is built 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 + +maximum number of packets the qdisc may hold queued at a time. + +.SS delay +adds the chosen delay to the packets outgoing to chosen network interface. The +optional parameters allows one to introduce a delay variation and a correlation. +Delay and jitter values are expressed in ms while correlation is percentage. + +.SS distribution +allow the user to choose the delay distribution. If not specified, the default +distribution is Normal. Additional parameters allow one to consider situations in +which network has variable delays depending on traffic flows concurring on the +same path, that causes several 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 possible to add a correlation, but this option +is now deprecated due to the noticed bad behavior. + +.SS loss state +adds packet losses according to the 4-state Markov using the transition +probabilities as input parameters. The parameter p13 is mandatory and if used +alone corresponds to the Bernoulli model. The optional parameters allows one 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 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 ecn +can be used optionally to mark packets instead of dropping them. A loss model +has to be used for this to be enabled. + +.SS corrupt +allows the emulation of 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 queuing +them. It is also possible to add a correlation through the proper parameter. + +.SS reorder +to use reordering, a delay option must be specified. There are two ways to use +this option (assuming 'delay 10ms' in the options list). + +.B "reorder " +.I 25% 50% +.B "gap" +.I 5 +.br +in this first example, the first 4 (gap - 1) packets are delayed by 10ms and +subsequent packets are sent immediately with a probability of 0.25 (with +correlation of 50% ) or delayed with a probability of 0.75. After a packet is +reordered, the process restarts i.e. the next 4 packets are delayed and +subsequent packets are sent immediately or delayed based on reordering +probability. To cause a repeatable pattern where every 5th packet is reordered +reliably, a reorder probability of 100% can be used. + +.B reorder +.I 25% 50% +.br +in this second example 25% of packets are sent immediately (with correlation of +50%) while the others are delayed by 10 ms. + +.SS rate +delay packets based on packet size and is a replacement for +.IR TBF . +Rate can be +specified in common units (e.g. 100kbit). Optional +.I PACKETOVERHEAD +(in bytes) specify an per packet overhead and can be negative. A positive value can be +used to simulate additional link layer headers. A negative value can be used to +artificial strip the Ethernet header (e.g. -14) and/or simulate a link layer +header compression scheme. The third parameter - an unsigned value - specify +the cellsize. Cellsize can be used to simulate link layer schemes. ATM for +example has an payload cellsize of 48 bytes and 5 byte per cell header. If a +packet is 50 byte then ATM must use two cells: 2 * 48 bytes payload including 2 +* 5 byte header, thus consume 106 byte on the wire. The last optional value +.I CELLOVERHEAD +can be used to specify per cell overhead - for our ATM example 5. +.I CELLOVERHEAD +can be negative, but use negative values with caution. + +Note that rate throttling is limited by several factors: the kernel clock +granularity avoid a perfect shaping at a specific level. This will show up in +an artificial packet compression (bursts). Another influence factor are network +adapter buffers which can also add artificial delay. + +.SS slot +defer delivering accumulated packets to within a slot. Each available slot can be +configured with a minimum delay to acquire, and an optional maximum delay. +Alternatively it can be configured with the distribution similar to +.BR distribution +for +.BR delay +option. Slot delays can be specified in nanoseconds, microseconds, milliseconds or seconds +(e.g. 800us). Values for the optional parameters +.I BYTES +will limit the number of bytes delivered per slot, and/or +.I PACKETS +will limit the number of packets delivered per slot. + +These slot options can provide a crude approximation of bursty MACs such as +DOCSIS, WiFi, and LTE. + +Note that slotting is limited by several factors: the kernel clock granularity, +as with a rate, and attempts to deliver many packets within a slot will be +smeared by the timer resolution, and by the underlying native bandwidth also. + +It is possible to combine slotting with a rate, in which case complex behaviors +where either the rate, or the slot limits on bytes or packets per slot, govern +the actual delivered rate. + +.SH LIMITATIONS +The main known limitation of Netem are related to timer granularity, since +Linux is not a real-time operating system. + +.SH EXAMPLES +.PP +tc qdisc add dev eth0 root netem rate 5kbit 20 100 5 +.RS 4 +delay all outgoing packets on device eth0 with a rate of 5kbit, a per packet +overhead of 20 byte, a cellsize of 100 byte and a per celloverhead of 5 byte: +.RE + +.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, (https://wiki.linuxfoundation.org/networking/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> |