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iperf3 - Online in the Cloud

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iperf3 - perform network throughput tests


iperf3 -s [ options ]
iperf3 -c server [ options ]


iperf3 is a tool for performing network throughput measurements. It can test either TCP
or UDP throughput. To perform an iperf3 test the user must establish both a server and a


-p, --port n
set server port to listen on/connect to to n (default 5201)

-f, --format
[kmKM] format to report: Kbits, Mbits, KBytes, MBytes

-i, --interval n
pause n seconds between periodic bandwidth reports; default is 1, use 0 to disable

-F, --file name
client-side: read from the file and write to the network, instead of using random
data; server-side: read from the network and write to the file, instead of throwing
the data away

-A, --affinity n/n,m
Set the CPU affinity, if possible (linux only). On both the client and server you
can set the local affinity; in addition, on the client side you can override the
server's affinity for just that one test, using the n,m form.

-V, --verbose
give more detailed output

-J, --json
output in JSON format

-d, --debug
emit debugging output. Primarily (perhaps exclusively) of use to developers.

-v, --version
show version information and quit

-h, --help
show a help synopsis


-s, --server
run in server mode

-D, --daemon
run the server in background as a daemon

-1, --one-off
handle one client connection, then exit.


-c, --client host
run in client mode, connecting to the specified server

-u, --udp
use UDP rather than TCP

-b, --bandwidth n[KM]
set target bandwidth to n bits/sec (default 1 Mbit/sec for UDP, unlimited for TCP).
If there are multiple streams (-P flag), the bandwidth limit is applied separately
to each stream. You can also add a '/' and a number to the bandwidth specifier.
This is called "burst mode". It will send the given number of packets without
pausing, even if that temporarily exceeds the specified bandwidth limit. Setting
the target bandwidth to 0 will disable bandwidth limits (particularly useful for
UDP tests).

-t, --time n
time in seconds to transmit for (default 10 secs)

-n, --bytes n[KM]
number of bytes to transmit (instead of -t)

-k, --blockcount n[KM]
number of blocks (packets) to transmit (instead of -t or -n)

-l, --length n[KM]
length of buffer to read or write (default 128 KB for TCP, 8KB for UDP)

-P, --parallel n
number of parallel client streams to run

-R, --reverse
run in reverse mode (server sends, client receives)

-w, --window n[KM]
window size / socket buffer size (this gets sent to the server and used on that
side too)

-B, --bind n[KM]
bind to a specific interface or multicast address

-M, --set-mss n
set TCP maximum segment size (MTU - 40 bytes)

-N, --no-delay
set TCP no delay, disabling Nagle's Algorithm

-4, --version4
only use IPv4

-6, --version6
only use IPv6

-S, --tos n
set the IP 'type of service'

-L, --flowlabel n
set the IPv6 flow label (currently only supported on Linux)

-Z, --zerocopy
Use a "zero copy" method of sending data, such as sendfile(2), instead of the usual

-O, --omit n
Omit the first n seconds of the test, to skip past the TCP slow-start period.

-T, --title str
Prefix every output line with this string.

-C, --linux-congestion algo
Set the congestion control algorithm (linux only).

Get the output from the server. The output format is determined by the server (in
particular, if the server was invoked with the --json flag, the output will be in
JSON format, otherwise it will be in human-readable format). If the client is run
with --json, the server output is included in a JSON object; otherwise it is
appended at the bottom of the human-readable output.


Iperf was originally written by Mark Gates and Alex Warshavsky. Man page and maintence by
Jon Dugan <jdugan at x1024 dot net>. Other contributions from Ajay Tirumala, Jim
Ferguson, Feng Qin, Kevin Gibbs, John Estabrook <jestabro at ncsa.uiuc.edu>, Andrew
Gallatin <gallatin at gmail.com>, Stephen Hemminger <shemminger at linux-foundation.org>

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