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diff --git a/upstream/archlinux/man8/tc-netem.8 b/upstream/archlinux/man8/tc-netem.8 new file mode 100644 index 00000000..a4cc0d61 --- /dev/null +++ b/upstream/archlinux/man8/tc-netem.8 @@ -0,0 +1,405 @@ +.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 " ] [ " SEED " ]" + +.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 " ]" + +.IR SEED " := " +.B seed +.I VALUE + +.SH DESCRIPTION +The +.B netem +queue discipline provides Network Emulation functionality +for testing protocols by emulating the properties of real-world networks. + +The queue discipline provides one or more network impairments to packets +such as: delay, loss, duplication, and packet corruption. + +.SH OPTIONS +.TP +.BI limit " COUNT" +Limits the maximum number of packets the qdisc may hold when doing delay. + +.TP +.B delay +.IR TIME " [ " JITTER " [ " CORRELATION " ]]]" +.br +Delays the packets before sending. +The optional parameters allow introducing a delay variation and a correlation. +Delay and jitter values are expressed in milliseconds; +Correlation is set by specifying a percent of how much the previous delay +will impact the current random value. + +.TP +.BI distribution " TYPE" +Specifies a pattern for delay distribution. +.RS +.TP +.B uniform +Use an equally weighted distribution of packet delays. +.TP +.B normal +Use a Gaussian distribution of delays. +Sometimes called a Bell Curve. +.TP +.B pareto +Use a Pareto distribution of packet delays. +This is useful to emulate long-tail distributions. +.TP +.B paretonormal +This is a mix of +.B pareto +and +.B normal +distribution which has properties of both Bell curve and long tail. +.RE + +.TP +.BI loss " MODEL" +Drop packets based on a loss model. +.I MODEL +can be one of +.RS +.TP +.BI random " PERCENT" +Each packet loss is independent. +.TP +.BI state " P13 [ P31 [ P32 [ P23 P14 ]]]" +Use a 4-state Markov chain to describe packet loss. +.br +.I P13 +is the packet loss. +Optional parameters extend the model to 2-state +.IR P31 , +3-state +.IR P23 , +.I P32 +and 4-state +.IR P14 . + +The Markov chain states are: +.RS +.TP +.B 1 +good packet reception (no loss). +.TP +.B 2 +good reception within a burst. +.TP +.B 3 +burst losses. +.TP +.B 4 +independent losses. +.RE + +.TP +.BI gemodel " PERCENT [ R [ 1-H [ 1-K ]]]" +Use a Gilbert-Elliot (burst loss) model +based on: +.RS +.TP +.I PERCENT +probability of starting bad (lossy) state. +.TP +.I R +probability of exiting bad state. +.TP +.I "1-H" +loss probability in bad state. +.TP +.I "1-K" +loss probability in good state. +.RE +.RE + +.TP +.B ecn +Use +Explicit Congestion Notification (ECN) +to mark packets instead of dropping them. +A loss model has to be used for this to be enabled. +.TP +.BI corrupt " PERCENT" +modifies the contents of the packet at a random position +based on +.IR PERCENT . +.TP +.BI duplicate " PERCENT" +creates a copy of the packet before queuing. +.TP +.BI reorder " PERCENT" +modifies the order of packet in the queue. +.TP +.BI gap " DISTANCE" +sends some packets immediately. +The first packets +.I "(DISTANCE - 1)" +are delayed and the next packet is sent immediately. + +.TP +.BI rate " RATE [ PACKETOVERHEAD [ CELLSIZE [ CELLOVERHEAD ]]]" +Delays packets based on packet size to emulate a fixed link speed. +Optional parameters: +.RS +.TP +.I PACKETOVERHEAD +Specify a per packet overhead in bytes. +Used to simulate additional link layer headers. +A negative value can be used to simlate when the Ethernet header is +stripped (e.g. -14) or header compression is used. +.TP +.I CELLSIZE +simulate link layer schemes like ATM. +.TP +.I CELLOVERHEAD +specify per cell overhead. +.RE + +Rate throttling impacted by several factors including the kernel clock +granularity. This will show up in an artificial packet compression (bursts). + +.TP +.BI slot " MIN_DELAY [ MAX_DELAY ]" +allows emulating slotted networks. +Defer delivering accumulated packets to within a slot. +Each available slot is configured with a minimum delay to acquire, +and an optional maximum delay. +.TP +.B slot distribution +allows configuring based on distribution similar to +.B distribution +option for packet delays. + +These slot options can provide a crude approximation of bursty MACs such as +DOCSIS, WiFi, and LTE. + +Slot emulation 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. + +.TP +.BI seed " VALUE" +Specifies a seed to guide and reproduce the randomly generated +loss or corruption events. + +.SH LIMITATIONS +Netem is limited by the timer granularity in the kernel. +Rate and delay maybe impacted by clock interrupts. +.PP +Mixing forms of reordering may lead to unexpected results. +For any method of reordering to work, some delay is necessary. +If the delay is less than the inter-packet arrival time then +no reordering will be seen. +Due to mechanisms like TSQ (TCP Small Queues), for TCP performance test +results to be realistic netem must be placed on the ingress of the +receiver host. +.PP +Combining netem with other qdisc is possible but may not always +work because netem use skb control block to set delays. + +.SH EXAMPLES +.PP +.EX +# tc qdisc add dev eth0 root netem delay 100ms +.EE +.RS 4 +Add fixed amount of delay to all packets going out on device eth0. +Each packet will have added delay of 100ms ± 10ms. +.RE +.PP +.EX +# tc qdisc change dev eth0 root netem delay 100ms 10ms 25% +.EE +.RS 4 +This causes the added delay of 100ms ± 10ms +and the next packet delay value will be biased by 25% on the most recent delay. +This isn't a true statistical correlation, but an approximation. +.RE +.PP +.EX +# tc qdisc change dev eth0 root netem delay 100ms 20ms distribution normal +.EE +.RS 4 +This delays packets according to a normal distribution (Bell curve) +over a range of 100ms ± 20ms. +.RE +.PP +.EX +# tc qdisc change dev eth0 root netem loss 0.1% +.EE +.RS 4 +This causes 1/10th of a percent (i.e 1 out of 1000) packets to be +randomly dropped. + +An optional correlation may also be added. +This causes the random number generator to be less random and can be used to emulate packet burst losses. +.RE +.PP +.EX +# tc qdisc change dev eth0 root netem duplicate 1% +.EE +.RS 4 +This causes one percent of the packets sent on eth0 to be duplicated. +.RE +.PP +.EX +# tc qdisc change dev eth0 root netem loss 0.3% 25% +.EE +.RS 4 +This will cause 0.3% of packets to be lost, +and each successive probability depends is biased by 25% of the previous one. +.RE +.PP +There are two different ways to specify reordering. +The gap method uses a fixed sequence and reorders every Nth packet. +.EX +# tc qdisc change dev eth0 root netem gap 5 delay 10ms +.EE +.RS 4 +This causes every 5th (10th, 15th, …) packet to go to be sent immediately +and every other packet to be delayed by 10ms. +This is predictable and useful for base protocol testing like reassembly. +.RE +.PP +The reorder form uses a percentage of the packets to get misordered. +.EX +# tc qdisc change dev eth0 root netem delay 10ms reorder 25% 50% +.EE +In this example, 25% of packets (with a correlation of 50%) will get sent immediately, others will be delayed by 10ms. +.PP +Packets will also get reordered if jitter is large enough. +.EX +# tc qdisc change dev eth0 root netem delay 100ms 75ms +.EE +.RS 4 +If the first packet gets a random delay of 100ms (100ms base - 0ms jitter) +and the second packet is sent 1ms later and gets a delay of 50ms (100ms base - 50ms jitter); +the second packet will be sent first. +This is because the queue discipline tfifo inside netem, +keeps packets in order by time to send. +.RE +.PP +If you don't want this behavior then replace the internal +queue discipline tfifo with a simple FIFO queue discipline. +.EX +# tc qdisc add dev eth0 root handle 1: netem delay 10ms 100ms +# tc qdisc add dev eth0 parent 1:1 pfifo limit 1000 +.EE + +.PP +Example of using rate control and cells size. +.EX +# tc qdisc add dev eth0 root netem rate 5kbit 20 100 5 +.EE +.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 bytes. +.RE + +.PP +It is possible to selectively apply impairment using traffic classification. +.EX +# tc qdisc add dev eth0 root handle 1: prio +# tc qdisc add dev eth0 parent 1:3 handle 30: \ + tbf rate 20kbit buffer 1600 limit 3000 +# tc qdisc add dev eth0 parent 30:1 handle 31: \ + netem delay 200ms 10ms distribution normal +# tc filter add dev eth0 protocol ip parent 1:0 prio 3 u32 \ + match ip dst 65.172.181.4/32 flowid 1:3 +.EE +.RS 4 +This example uses a priority queueing discipline; +a TBF is added to do rate control; and a simple netem delay. +A filter classifies all packets going to 65.172.181.4 as being priority 3. +.PP +.SH SOURCES +.IP " 1. " 4 +Hemminger S. , "Network Emulation with NetEm", Open Source Development Lab, +April 2005 +.UR http://devresources.linux-foundation.org/shemminger/netem/LCA2005_paper.pdf +.UE + +.IP " 2. " 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 +.UR http://netgroup.uniroma2.it/NetemCLG +.UE + +.SH SEE ALSO +.BR tc (8) + +.SH AUTHOR +Netem was written by Stephen Hemminger at Linux foundation and was +inspired by NISTnet. + +Original manpage was created by Fabio Ludovici +<fabio.ludovici at yahoo dot it> and Hagen Paul Pfeifer +<hagen@jauu.net>. |