iperf

code format="html4strict" Iperf tests:

no arg. -b -r -d -w Default settings Data format Bi-directional bandwidth Simultaneous bi-directional bandwidth TCP Window size -p, -t, -i -u, -b -m -M -P -h	 Port, timing and interval UDP tests, bandwidth settings Maximum Segment Size display Maximum Segment Size settings Parallel tests help Jperf:

no arg. -d -u, -b	 Default settings Simultaneous bi-directional bandwidth UDP tests, bandwidth settings

Default Iperf settings: Also check "Jperf section.

By default, the Iperf client connects to the Iperf server on the TCP port 5001 and the bandwidth displayed by Iperf is the bandwidth from the client to the server. If you want to use UDP tests, use the -u argument. The -d and -r Iperf client arguments measure the bi-directional bandwidths. (See further on this tutorial)

Client side:


 * 1) iperf -c 10.1.1.1

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16384 Byte (default)

[ 3] local 10.6.2.5 port 33453 connected with 10.1.1.1 port 5001 [ 3]  0.0-10.2 sec   1.26 MBytes   1.05 Mbits/sec

Server side:


 * 1) iperf -s

Server listening on TCP port 5001 TCP window size: 8.00 KByte (default)

[852] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 33453 [ ID]  Interval          Transfer       Bandwidth [852]  0.0-10.6 sec   1.26 MBytes   1.03 Mbits/sec

Data formatting: (-f argument)

The -f argument can display the results in the desired format: bits(b), bytes(B), kilobits(k), kilobytes(K), megabits(m), megabytes(M), gigabits(g) or gigabytes(G). Generally the bandwidth measures are displayed in bits (or Kilobits, etc ...) and an amount of data is displayed in bytes (or Kilobytes, etc ...). As a reminder, 1 byte is equal to 8 bits and, in the computer science world, 1 kilo is equal to 1024 (2^10). For example: 100'000'000 bytes is not equal to 100 Mbytes but to 100'000'000/1024/1024 = 95.37 Mbytes.

Client side:


 * 1) iperf -c 10.1.1.1 -f b

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16384 Byte (default)

[ 3] local 10.6.2.5 port 54953 connected with 10.1.1.1 port 5001 [ 3]  0.0-10.2 sec   1359872 Bytes   1064272 bits/sec

Server side:


 * 1) iperf -s

Server listening on TCP port 5001 TCP window size: 8.00 KByte (default)

[852] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 33453 [ ID]  Interval          Transfer       Bandwidth [852]  0.0-10.6 sec   920 KBytes   711 Kbits/sec

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Bi-directional bandwidth measurement: (-r argument)

The Iperf server connects back to the client allowing the bi-directional bandwidth measurement. By default, only the bandwidth from the client to the server is measured. If you want to measure the bi-directional bandwidth simultaneously, use the -d keyword. (See next test.)

Client side:


 * 1) iperf -c 10.1.1.1 -r

Server listening on TCP port 5001 TCP window size: 85.3 KByte (default)

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16.0 KByte (default)

[ 5] local 10.6.2.5 port 35726 connected with 10.1.1.1 port 5001 [ 5]  0.0-10.0 sec   1.12 MBytes   936 Kbits/sec [ 4] local 10.6.2.5 port 5001 connected with 10.1.1.1 port 1640 [ 4]  0.0-10.1 sec   74.2 MBytes   61.7 Mbits/sec

Server side:


 * 1) iperf -s

Server listening on TCP port 5001 TCP window size: 8.00 KByte (default)

[852] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 54355 [ ID]  Interval          Transfer        Bandwidth [852]  0.0-10.1 sec   1.15 MBytes   956 Kbits/sec

Client connecting to 10.6.2.5, TCP port 5001 TCP window size: 8.00 KByte (default)

[824] local 10.1.1.1 port 1646 connected with 10.6.2.5 port 5001 [ ID]  Interval          Transfer        Bandwidth [824]  0.0-10.0 sec   73.3 MBytes   61.4 Mbits/sec

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Simultaneous bi-directional bandwidth measurement: (-d argument) Also check the "Jperf" section.

To measure the bi-directional bandwidths simultaneousely, use the -d argument. If you want to test the bandwidths sequentially, use the -r argument (see previous test). By default (ie: without the -r or -d arguments), only the bandwidth from the client to the server is measured.

Client side:


 * 1) iperf -c 10.1.1.1 -d

Server listening on TCP port 5001 TCP window size: 85.3 KByte (default)

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16.0 KByte (default)

[ 5] local 10.6.2.5 port 60270 connected with 10.1.1.1 port 5001 [ 4] local 10.6.2.5 port 5001 connected with 10.1.1.1 port 2643 [ 4] 0.0-10.0 sec 76.3 MBytes 63.9 Mbits/sec [ 5] 0.0-10.1 sec 1.55 MBytes 1.29 Mbits/sec

Server side:


 * 1) iperf -s

Server listening on TCP port 5001 TCP window size: 8.00 KByte (default)

[852] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 60270

Client connecting to 10.6.2.5, TCP port 5001 TCP window size: 8.00 KByte (default)

[800] local 10.1.1.1 port 2643 connected with 10.6.2.5 port 5001 [ ID]  Interval          Transfer       Bandwidth [800]  0.0-10.0 sec   76.3 MBytes   63.9 Mbits/sec [852]  0.0-10.1 sec   1.55 MBytes   1.29 Mbits/sec

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TCP Window size: (-w argument)

The TCP window size is the amount of data that can be buffered during a connection without a validation from the receiver. It can be between 2 and 65,535 bytes. On Linux systems, when specifying a TCP buffer size with the -w argument, the kernel allocates double as much as indicated.

Client side:

WARNING: TCP window size set to 2000 bytes. A small window size will give poor performance. See the Iperf documentation.
 * 1) iperf -c 10.1.1.1 -w 2000

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 3.91 KByte (WARNING: requested 1.95 KByte)

[ 3] local 10.6.2.5 port 51400 connected with 10.1.1.1 port 5001 [ 3]  0.0-10.1 sec   704 KBytes   572 Kbits/sec

Server side:


 * 1) iperf -s -w 4000

Server listening on TCP port 5001 TCP window size: 3.91 KByte

[852] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 51400 [ ID]  Interval          Transfer       Bandwidth [852]  0.0-10.1 sec   704 KBytes   570 Kbits/sec

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Communication port (-p), timing (-t) and interval (-i):

The Iperf server communication port can be changed with the -p argument. It must be configured on the client and the server with the same value, default is TCP port 5001. The -t argument specifies the test duration time in seconds, default is 10 secs. The -i argument indicates the interval in seconds between periodic bandwidth reports.

Client side:


 * 1) iperf -c 10.1.1.1 -p 12000 -t 20 -i 2

Client connecting to 10.1.1.1, TCP port 12000 TCP window size: 16.0 KByte (default)

[ 3] local 10.6.2.5 port 58316 connected with 10.1.1.1 port 12000 [ 3]   0.0- 2.0 sec    224 KBytes    918 Kbits/sec [ 3]   2.0- 4.0 sec    368 KBytes    1.51 Mbits/sec [ 3]   4.0- 6.0 sec    704 KBytes    2.88 Mbits/sec [ 3]   6.0- 8.0 sec    280 KBytes    1.15 Mbits/sec [ 3]   8.0-10.0 sec    208 KBytes    852 Kbits/sec [ 3]  10.0-12.0 sec   344 KBytes    1.41 Mbits/sec [ 3]  12.0-14.0 sec   208 KBytes    852 Kbits/sec [ 3]  14.0-16.0 sec   232 KBytes    950 Kbits/sec [ 3]  16.0-18.0 sec   232 KBytes    950 Kbits/sec [ 3]  18.0-20.0 sec   264 KBytes    1.08 Mbits/sec [ 3]   0.0-20.1 sec   3.00 MBytes   1.25 Mbits/sec

Server side:


 * 1) iperf -s -p 12000

Server listening on TCP port 12000 TCP window size: 8.00 KByte (default)

[852] local 10.1.1.1 port 12000 connected with 10.6.2.5 port 58316 [ ID] Interval Transfer Bandwidth [852]  0.0-20.1 sec   3.00 MBytes   1.25 Mbits/sec

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UDP tests: (-u), bandwidth settings (-b) Also check the "Jperf" section.

The UDP tests with the -u argument will give invaluable information about the jitter and the packet loss. If you don't specify the -u argument, Iperf uses TCP. To keep a good link quality, the packet loss should not go over 1 %. A high packet loss rate will generate a lot of TCP segment retransmissions which will affect the bandwidth.

The jitter is basically the latency variation and does not depend on the latency. You can have high response times and a very low jitter. The jitter value is particularly important on network links supporting voice over IP (VoIP) because a high jitter can break a call. The -b argument allows the allocation if the desired bandwidth.

Client side:


 * 1) iperf -c 10.1.1.1 -u -b 10m

Client connecting to 10.1.1.1, UDP port 5001 Sending 1470 byte datagrams UDP buffer size: 108 KByte (default)

[ 3] local 10.6.2.5 port 32781 connected with 10.1.1.1 port 5001 [ 3]  0.0-10.0 sec   11.8 MBytes   9.89 Mbits/sec [ 3] Sent 8409 datagrams [ 3] Server Report: [ 3]  0.0-10.0 sec   11.8 MBytes   9.86 Mbits/sec   2.617 ms   9/ 8409   (0.11%)

Server side:


 * 1) iperf -s -u -i 1

Server listening on UDP port 5001 Receiving 1470 byte datagrams UDP buffer size: 8.00 KByte (default)

[904] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 32781 [ ID]  Interval         Transfer        Bandwidth         Jitter        Lost/Total Datagrams [904]  0.0- 1.0 sec   1.17 MBytes   9.84 Mbits/sec   1.830 ms   0/ 837   (0%) [904]  1.0- 2.0 sec   1.18 MBytes   9.94 Mbits/sec   1.846 ms   5/ 850   (0.59%) [904]  2.0- 3.0 sec   1.19 MBytes   9.98 Mbits/sec   1.802 ms   2/ 851   (0.24%) [904]  3.0- 4.0 sec   1.19 MBytes   10.0 Mbits/sec   1.830 ms   0/ 850   (0%) [904]  4.0- 5.0 sec   1.19 MBytes   9.98 Mbits/sec   1.846 ms   1/ 850   (0.12%) [904]  5.0- 6.0 sec   1.19 MBytes   10.0 Mbits/sec   1.806 ms   0/ 851   (0%) [904]  6.0- 7.0 sec   1.06 MBytes   8.87 Mbits/sec   1.803 ms   1/ 755   (0.13%) [904]  7.0- 8.0 sec   1.19 MBytes   10.0 Mbits/sec   1.831 ms   0/ 850   (0%) [904]  8.0- 9.0 sec   1.19 MBytes   10.0 Mbits/sec   1.841 ms   0/ 850   (0%) [904]  9.0-10.0 sec   1.19 MBytes   10.0 Mbits/sec   1.801 ms   0/ 851   (0%) [904]  0.0-10.0 sec   11.8 MBytes   9.86 Mbits/sec   2.618 ms   9/ 8409  (0.11%)

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Maximum Segment Size (-m argument) display:

The Maximum Segment Size (MSS) is the largest amount of data, in bytes, that a computer can support in a single, unfragmented TCP segment. It can be calculated as follows: MSS = MTU - TCP & IP headers The TCP & IP headers are equal to 40 bytes. The MTU or Maximum Transmission Unit is the greatest amount of data that can be transferred in a frame. Here are some default MTU size for different network topology: Ethernet - 1500 bytes: used in a LAN. PPPoE - 1492 bytes: used on ADSL links. Token Ring (16Mb/sec) - 17914 bytes: old technology developed by IBM. Dial-up - 576 bytes

Generally, a higher MTU (and MSS) brings higher bandwidth efficiency

Client side:


 * 1) iperf -c 10.1.1.1 -m

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16.0 KByte (default)

[ 3] local 10.6.2.5 port 41532 connected with 10.1.1.1 port 5001 [ 3]  0.0-10.2 sec   1.27 MBytes   1.04 Mbits/sec [ 3] MSS size 1448 bytes (MTU 1500 bytes, ethernet)

Here the MSS is not equal to 1500 - 40 but to 1500 - 40 - 12 (Timestamps option) = 1448

Server side:

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 * 1) iperf -s

Maximum Segment Size (-M argument) settings:

Use the -M argument to change the MSS. (See the previous test for more explanations about the MSS)

WARNING: attempt to set TCP maximum segment size to 1300, but got 536
 * 1) iperf -c 10.1.1.1 -M 1300 -m

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16.0 KByte (default)

[ 3] local 10.6.2.5 port 41533 connected with 10.1.1.1 port 5001 [ 3]  0.0-10.1 sec   4.29 MBytes   3.58 Mbits/sec [ 3] MSS size 1288 bytes (MTU 1328 bytes, unknown interface)

Server side:

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 * 1) iperf -s

Parallel tests (-P argument):

Use the -P argument to run parallel tests.

Client side:


 * 1) iperf -c 10.1.1.1 -P 2

Client connecting to 10.1.1.1, TCP port 5001 TCP window size: 16.0 KByte (default)

[ 3] local 10.6.2.5 port 41534 connected with 10.1.1.1 port 5001 [ 4] local 10.6.2.5 port 41535 connected with 10.1.1.1 port 5001 [ 4]    0.0-10.1 sec   1.35 MBytes   1.12 Mbits/sec [ 3]    0.0-10.1 sec   1.35 MBytes   1.12 Mbits/sec [SUM] 0.0-10.1 sec   2.70 MBytes   2.24 Mbits/sec

Server side:

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 * 1) iperf -s

Iperf help:

Usage: iperf [-s|-c host] [options] iperf [-h|--help] [-v|--version]
 * 1) iperf -h

Client/Server: -f -i -l -m -p -u -w -B -C -M -N -V	--format --interval --len --print_mss --port --udp --window --bind --compatibility --mss --nodelay --IPv6Version	[kmKM]
 * 1) [KM]
 * 1) [KM]



"host"
 * 1) [KM]



format to report: Kbits, Mbits, KBytes, MBytes seconds between periodic bandwidth reports length of buffer to read or write (default 8 KB) print TCP maximum segment size (MTU - TCP/IP header) server port to listen on/connect to use UDP rather than TCP TCP window size (socket buffer size) bind to "host", an interface or multicast address for use with older versions does not sent extra msgs set TCP maximum segment size (MTU - 40 bytes) set TCP no delay, disabling Nagle's Algorithm Set the domain to IPv6 Server specific: -s -U -D	--server --single_udp --daemon

run in server mode run in single threaded UDP mode run the server as a daemon Client specific: -b -c -d -n -r -t -F -I -L -P -T	--bandwidth --client --dualtest --num --tradeoff --time --fileinput --stdin --listenport --parallel --ttl	 #[KM] "host"


 * 1) [KM]

"name"

run in client mode, connecting to "host" Do a bidirectional test simultaneously number of bytes to transmit (instead of -t) Do a bidirectional test individually time in seconds to transmit for (default 10 secs) input the data to be transmitted from a file input the data to be transmitted from stdin port to recieve bidirectional tests back on number of parallel client threads to run time-to-live, for multicast (default 1) Miscellaneous: -h -v	--help --version print this message and quit print version information and quit
 * 1) 	 for UDP, bandwidth to send at in bits/sec (default 1 Mbit/sec, implies -u)
 * 1) 	 for UDP, bandwidth to send at in bits/sec (default 1 Mbit/sec, implies -u)
 * 1) 	 for UDP, bandwidth to send at in bits/sec (default 1 Mbit/sec, implies -u)

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