man/man8/tc-netem.8 - maze/iproute2 - Git at Google

 .TH NETEM 8 "25 November 2011" "iproute2" "Linux"
 .SH NAME
 NetEm \- Network Emulator
 .SH SYNOPSIS
 .B tc qdisc ... dev
 dev
 .B ] add netem  [ limit
 packets
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ logging
 LEVEL ]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ delay
 TIME [ JITTER [CORRELATION]]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ distribution
 {uniform|normal|pareto|paretonormal} ]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ drop
 PERCENT [CORRELATION]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ loss
 PERCENT [CORRELATION]]
 .B ]


 .B tc qdisc ... dev
 dev
 .B ] add netem [ query ] [ loss_GI
 ploss [burst_length [density [pisol [good_burst_length]]]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ query ] [ loss_4state
 [p13 [p31 [p32 [p23 [p14]]]]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem  [ loss_gilb_ell
 p [r [1-h [1-k]]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem  [ loss_gilb_ell_4s
 p [r [1-h [1-k]]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem [ loss_pattern
 FILENAME [REPETITIONS]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem  [ corrupt
 PERCENT [CORRELATION]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem  [ duplicate
 PERCENT [CORRELATION]]
 .B ]

 .B tc qdisc ... dev
 dev
 .B ] add netem  [ reorder
 PRECENT [CORRELATION] [ gap DISTANCE ]]
 .B ]

 .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:

 .B limit
 packets

 limits the effect of selected options to the indicated number of next packets.

 .B logging
 LEVEL

 sets a logging level. Actually it works with loss_GI, loss_4state, loss_bern,
 loss_gilb, loss_gilb_ell, loss_gilb_ell_4s, loss_pattern options. The default
 value is level 0, which means that no data will be logged. When logging level
 is set to 1 the kernel logs will include a line like "netem loss event
 algorithm [type] x RFPLE y" for each loss event. The acronym RFPLE means
 "Received From Previous Loss Event" and it counts the number y of good packets
 received between two loss events while x is the number of all lost packets and
 algorithm refers to the selected loss generation algorithm (4-state, gilb_ell
 or deterministic). The type label applies only to the GI algorithm and can be
 burst or isolated.

 .B delay
 TIME [ JITTER [CORRELATION]]]

 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.

 .B distribution
 {uniform|normal|pareto|paretonormal}

 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.

 .B drop
 PERCENT [CORRELATION]

 OR

 .B loss
 PERCENT [CORRELATION]

 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.

 .B query

 enables the query mode. It applies to loss_GI and loss_4state options. If it is
 used with the loss_GI option, the transition probabilities which correspond to
 the input intuitive parameters are calculated and printed to screen, without
 copying them in the netem qdisc. Similarly, if it is used with the loss_4state
 option, it calculates and prints the intuitive parameters that corresponds to
 the input transition probabilities.

 .B loss_GI
 ploss [burst_length [density [pisol [good_burst_length]]]]

 adds packet losses according to the GI (General and Intuitive) loss model,
 using the intuitive parameters. The parameter ploss is mandatory while the
 others are optional. The intuitive parameters are converted to the transition
 probabilities of the 4-state Markov model. If the only parameter specified is
 ploss, it corresponds to the Bernoulli model while the optional parameters
 allow to extend the model to 2-state (burst_length), 3-state (density), and
 4-state (pisol). If the good_burst_length is not specified the hyphotesis of
 statistical independence for the losses within the burst will be used.

 .B loss_4state
 p13 [p31 [p32 [p23 [p14]]]]

 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.

 .B loss_gilb_ell
 p [r [1-h [1-k]]]

 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.

 .B loss_gilb_ell_4s
 p [r [1-h [1-k]]]

 adds packet losses according to the Gilbert-Elliot-4s loss model. It is a
 particular version of the GI model which behaviour is very similar to the
 Gilbert-Elliot's. The input parameters are the same of the real Gilbert-Elliot
 model or its special cases. The transition probabilities and GI parameters that
 corresponds to the Gilbert-Elliot input parameters are calculated and, if the
 query mode is enabled, printed to screen. This option is included to study the
 correspondence between GI model and the models available in the literature, it
 has no practical use at the moment.

 .B loss_pattern
 FILENAME [REPETITIONS]

 adds packet losses according to a deterministic loss pattern. It reads from the
 text file FILENAME a sequence of "1" and "0" where "1" are the loss events and
 "0" are the regular transmission of packets . The parameter repetitions is
 optional and is the number of "replicas" of the loss pattern file. It is
 optional and by default is 0 which means infinite repetition of the loss
 pattern.

 .B corrupt
 PERCENT [CORRELATION]]

 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.

 .B duplicate
 PERCENT [CORRELATION]]

 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.

 .B reorder
 PRECENT [CORRELATION] [ gap DISTANCE ]]

 there are two ways to use this option:

 .B reorder
 gap 5 10 ms

 in this first example every 5th (10th, 15th) packet is sent immediately while
 other packets are delayed by 10 ms

 .B reorder
 25% 50%

 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; to the choice of Pseudo-Random
 Number Generator (PRNG) and the original loss model.

 .SH SOURCES
 .TP
 o
 Hemminger S. , "Network Emulation with NetEm", Open Source Development Lab,
 April 2005
 (http://devresources.linux-foundation.org/shemminger/netem/LCA2005_paper.pdf)

 .TP
 o
 Netem page from Linux foundation, (http://www.linuxfoundation.org/en/Net:Netem)

 .TP
 o
 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 OSDL 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>
	.TH NETEM 8 "25 November 2011" "iproute2" "Linux"
	.SH NAME
	NetEm \- Network Emulator
	.SH SYNOPSIS
	.B tc qdisc ... dev
	dev
	.B ] add netem [ limit
	packets
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ logging
	LEVEL ]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ delay
	TIME [ JITTER [CORRELATION]]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ distribution
	{uniform\|normal\|pareto\|paretonormal} ]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ drop
	PERCENT [CORRELATION]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ loss
	PERCENT [CORRELATION]]
	.B ]


	.B tc qdisc ... dev
	dev
	.B ] add netem [ query ] [ loss_GI
	ploss [burst_length [density [pisol [good_burst_length]]]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ query ] [ loss_4state
	[p13 [p31 [p32 [p23 [p14]]]]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ loss_gilb_ell
	p [r [1-h [1-k]]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ loss_gilb_ell_4s
	p [r [1-h [1-k]]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ loss_pattern
	FILENAME [REPETITIONS]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ corrupt
	PERCENT [CORRELATION]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ duplicate
	PERCENT [CORRELATION]]
	.B ]

	.B tc qdisc ... dev
	dev
	.B ] add netem [ reorder
	PRECENT [CORRELATION] [ gap DISTANCE ]]
	.B ]

	.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:

	.B limit
	packets

	limits the effect of selected options to the indicated number of next packets.

	.B logging
	LEVEL

	sets a logging level. Actually it works with loss_GI, loss_4state, loss_bern,
	loss_gilb, loss_gilb_ell, loss_gilb_ell_4s, loss_pattern options. The default
	value is level 0, which means that no data will be logged. When logging level
	is set to 1 the kernel logs will include a line like "netem loss event
	algorithm [type] x RFPLE y" for each loss event. The acronym RFPLE means
	"Received From Previous Loss Event" and it counts the number y of good packets
	received between two loss events while x is the number of all lost packets and
	algorithm refers to the selected loss generation algorithm (4-state, gilb_ell
	or deterministic). The type label applies only to the GI algorithm and can be
	burst or isolated.

	.B delay
	TIME [ JITTER [CORRELATION]]]

	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.

	.B distribution
	{uniform\|normal\|pareto\|paretonormal}

	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.

	.B drop
	PERCENT [CORRELATION]

	OR

	.B loss
	PERCENT [CORRELATION]

	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.

	.B query

	enables the query mode. It applies to loss_GI and loss_4state options. If it is
	used with the loss_GI option, the transition probabilities which correspond to
	the input intuitive parameters are calculated and printed to screen, without
	copying them in the netem qdisc. Similarly, if it is used with the loss_4state
	option, it calculates and prints the intuitive parameters that corresponds to
	the input transition probabilities.

	.B loss_GI
	ploss [burst_length [density [pisol [good_burst_length]]]]

	adds packet losses according to the GI (General and Intuitive) loss model,
	using the intuitive parameters. The parameter ploss is mandatory while the
	others are optional. The intuitive parameters are converted to the transition
	probabilities of the 4-state Markov model. If the only parameter specified is
	ploss, it corresponds to the Bernoulli model while the optional parameters
	allow to extend the model to 2-state (burst_length), 3-state (density), and
	4-state (pisol). If the good_burst_length is not specified the hyphotesis of
	statistical independence for the losses within the burst will be used.

	.B loss_4state
	p13 [p31 [p32 [p23 [p14]]]]

	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.

	.B loss_gilb_ell
	p [r [1-h [1-k]]]

	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.

	.B loss_gilb_ell_4s
	p [r [1-h [1-k]]]

	adds packet losses according to the Gilbert-Elliot-4s loss model. It is a
	particular version of the GI model which behaviour is very similar to the
	Gilbert-Elliot's. The input parameters are the same of the real Gilbert-Elliot
	model or its special cases. The transition probabilities and GI parameters that
	corresponds to the Gilbert-Elliot input parameters are calculated and, if the
	query mode is enabled, printed to screen. This option is included to study the
	correspondence between GI model and the models available in the literature, it
	has no practical use at the moment.

	.B loss_pattern
	FILENAME [REPETITIONS]

	adds packet losses according to a deterministic loss pattern. It reads from the
	text file FILENAME a sequence of "1" and "0" where "1" are the loss events and
	"0" are the regular transmission of packets . The parameter repetitions is
	optional and is the number of "replicas" of the loss pattern file. It is
	optional and by default is 0 which means infinite repetition of the loss
	pattern.

	.B corrupt
	PERCENT [CORRELATION]]

	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.

	.B duplicate
	PERCENT [CORRELATION]]

	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.

	.B reorder
	PRECENT [CORRELATION] [ gap DISTANCE ]]

	there are two ways to use this option:

	.B reorder
	gap 5 10 ms

	in this first example every 5th (10th, 15th) packet is sent immediately while
	other packets are delayed by 10 ms

	.B reorder
	25% 50%

	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; to the choice of Pseudo-Random
	Number Generator (PRNG) and the original loss model.

	.SH SOURCES
	.TP
	o
	Hemminger S. , "Network Emulation with NetEm", Open Source Development Lab,
	April 2005
	(http://devresources.linux-foundation.org/shemminger/netem/LCA2005_paper.pdf)

	.TP
	o
	Netem page from Linux foundation, (http://www.linuxfoundation.org/en/Net:Netem)

	.TP
	o
	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 OSDL 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>