IPERF3(1) ESnet IPERF3(1)
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NAME
iperf3 - perform network throughput tests
SYNOPSIS
iperf3 -s [ options ]
iperf3 -c server [ options ]
DESCRIPTION
iperf3 is a tool for performing network throughput measurements. It
can test TCP, UDP, or SCTP throughput. To perform an iperf3 test the
user must establish both a server and a client.
The iperf3 executable contains both client and server functionality.
An iperf3 server can be started using either of the -s or --server
command-line parameters, for example:
iperf3 -s
iperf3 --server
Note that many iperf3 parameters have both short (-s) and long (--
server) forms. In this section we will generally use the short form
of command-line flags, unless only the long form of a flag is
available.
By default, the iperf3 server listens on TCP port 5201 for connections
from an iperf3 client. A custom port can be specified by using the -p
flag, for example:
iperf3 -s -p 5002
After the server is started, it will listen for connections from
iperf3 clients (in other words, the iperf3 program run in client
mode). The client mode can be started using the -c command-line
option, which also requires a host to which iperf3 should connect.
The host can by specified by hostname, IPv4 literal, or IPv6 literal:
iperf3 -c iperf3.example.com
iperf3 -c 192.0.2.1
iperf3 -c 2001:db8::1
If the iperf3 server is running on a non-default TCP port, that port
number needs to be specified on the client as well:
iperf3 -c iperf3.example.com -p 5002
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The initial TCP connection is used to exchange test parameters,
control the start and end of the test, and to exchange test results.
This is sometimes referred to as the "control connection". The actual
test data is sent over a separate TCP connection, as a separate flow
of UDP packets, or as an independent SCTP connection, depending on
what protocol was specified by the client.
Normally, the test data is sent from the client to the server, and
measures the upload speed of the client. Measuring the download speed
from the server can be done by specifying the -R flag on the client.
This causes data to be sent from the server to the client.
iperf3 -c iperf3.example.com -p 5202 -R
Results are displayed on both the client and server. There will be at
least one line of output per measurement interval (by default a
measurement interval lasts for one second, but this can be changed by
the -i option). Each line of output includes (at least) the time
since the start of the test, amount of data transfered during the
interval, and the average bitrate over that interval. Note that the
values for each measurement interval are taken from the point of view
of the endpoint process emitting that output (in other words, the
output on the client shows the measurement interval data for the
client.
At the end of the test is a set of statistics that shows (at least as
much as possible) a summary of the test as seen by both the sender and
the receiver, with lines tagged accordingly. Recall that by default
the client is the sender and the server is the receiver, although as
indicated above, use of the -R flag will reverse these roles.
The client can be made to retrieve the server-side output for a given
test by specifying the --get-server-output flag.
Either the client or the server can produce its output in a JSON
structure, useful for integration with other programs, by passing it
the -J flag. Because the contents of the JSON structure are only
competely known after the test has finished, no JSON output will be
emitted until the end of the test.
iperf3 has a (overly) large set of command-line options that can be
used to set the parameters of a test. They are given in the "GENERAL
OPTIONS" section of the manual page below, as well as summarized in
iperf3's help output, which can be viewed by running iperf3 with the
-h flag.
GENERAL OPTIONS
-p, --port n
set server port to listen on/connect to to n (default 5201)
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-f, --format
[kmgtKMGT] format to report: Kbits/Mbits/Gbits/Tbits
-i, --interval n
pause n seconds between periodic throughput reports; default is
1, use 0 to disable
-F, --file name
Use a file as the source (on the sender) or sink (on the
receiver) of data, rather than just generating random data or
throwing it away. This feature is used for finding whether or
not the storage subsystem is the bottleneck for file transfers.
It does not turn iperf3 into a file transfer tool. The length,
attributes, and in some cases contents of the received file may
not match those of the original file.
-A, --affinity n/n,m
Set the CPU affinity, if possible (Linux and FreeBSD only). On
both the client and server you can set the local affinity by
using the n form of this argument (where n is a CPU number). In
addition, on the client side you can override the server's
affinity for just that one test, using the n,m form of argument.
Note that when using this feature, a process will only be bound
to a single CPU (as opposed to a set containing potentialy
multiple CPUs).
-B, --bind host
bind to a specific interface. If the host has multiple
interfaces, it will use the first interface by default.
-V, --verbose
give more detailed output
-J, --json
output in JSON format
--logfile file
send output to a log file.
--forceflush
force flushing output at every interval. Used to avoid buffering
when sending output to pipe.
-d, --debug
emit debugging output. Primarily (perhaps exclusively) of use to
developers.
-v, --version
show version information and quit
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-h, --help
show a help synopsis
SERVER SPECIFIC OPTIONS
-s, --server
run in server mode
-D, --daemon
run the server in background as a daemon
-I, --pidfile file
write a file with the process ID, most useful when running as a
daemon.
-1, --one-off
handle one client connection, then exit.
--rsa-private-key-path file
path to the RSA private key (not password-protected) used to
decrypt authentication credentials from the client (if built with
OpenSSL support).
--authorized-users-path file
path to the configuration file containing authorized users
credentials to run iperf tests (if built with OpenSSL support).
The file is a comma separated list of usernames and password
hashes; more information on the structure of the file can be
found in the EXAMPLES section.
CLIENT SPECIFIC OPTIONS
-c, --client host
run in client mode, connecting to the specified server. By
default, a test consists of sending data from the client to the
server, unless the -R flag is specified.
--sctp
use SCTP rather than TCP (FreeBSD and Linux)
-u, --udp
use UDP rather than TCP
--connect-timeout n
set timeout for establishing the initial control connection to
the server, in milliseconds. The default behavior is the
operating system's timeout for TCP connection establishment.
Providing a shorter value may speed up detection of a down iperf3
server.
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-b, --bitrate n[KM]
set target bitrate to n bits/sec (default 1 Mbit/sec for UDP,
unlimited for TCP/SCTP). If there are multiple streams (-P
flag), the throughput limit is applied separately to each stream.
You can also add a '/' and a number to the bitrate specifier.
This is called "burst mode". It will send the given number of
packets without pausing, even if that temporarily exceeds the
specified throughput limit. Setting the target bitrate to 0 will
disable bitrate limits (particularly useful for UDP tests). This
throughput limit is implemented internally inside iperf3, and is
available on all platforms. Compare with the --fq-rate flag.
This option replaces the --bandwidth flag, which is now
deprecated but (at least for now) still accepted.
--pacing-timer n[KMG]
set pacing timer interval in microseconds (default 1000
microseconds, or 1 ms). This controls iperf3's internal pacing
timer for the -b/--bitrate option. The timer fires at the
interval set by this parameter. Smaller values of the pacing
timer parameter smooth out the traffic emitted by iperf3, but
potentially at the cost of performance due to more frequent timer
processing.
--fq-rate n[KM]
Set a rate to be used with fair-queueing based socket-level
pacing, in bits per second. This pacing (if specified) will be
in addition to any pacing due to iperf3's internal throughput
pacing (-b/--bitrate flag), and both can be specified for the
same test. Only available on platforms supporting the
SO_MAX_PACING_RATE socket option (currently only Linux). The
default is no fair-queueing based pacing.
--no-fq-socket-pacing
This option is deprecated and will be removed. It is equivalent
to specifying --fq-rate=0.
-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. For TCP tests, the default
value is 128KB. In the case of UDP, iperf3 tries to dynamically
determine a reasonable sending size based on the path MTU; if
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that cannot be determined it uses 1460 bytes as a sending size.
For SCTP tests, the default size is 64KB.
--cport port
bind data streams to a specific client port (for TCP and UDP
only, default is to use an ephemeral port)
-P, --parallel n
number of parallel client streams to run. Note that iperf3 is
single threaded, so if you are CPU bound, this will not yield
higher throughput.
-R, --reverse
reverse the direction of a test, so that the server sends data to
the client
-w, --window n[KM]
window size / socket buffer size (this gets sent to the server
and used on that side too)
-M, --set-mss n
set TCP/SCTP maximum segment size (MTU - 40 bytes)
-N, --no-delay
set TCP/SCTP 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
--dscp dscp
set the IP DSCP bits. Both numeric and symbolic values are
accepted.
-L, --flowlabel n
set the IPv6 flow label (currently only supported on Linux)
-X, --xbind name
Bind SCTP associations to a specific subset of links using
sctp_bindx(3). The --B flag will be ignored if this flag is
specified. Normally SCTP will include the protocol addresses of
all active links on the local host when setting up an
association. Specifying at least one --X name will disable this
behaviour. This flag must be specified for each link to be
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included in the association, and is supported for both iperf
servers and clients (the latter are supported by passing the
first --X argument to bind(2)). Hostnames are accepted as
arguments and are resolved using getaddrinfo(3). If the --4 or
--6 flags are specified, names which do not resolve to addresses
within the specified protocol family will be ignored.
--nstreams n
Set number of SCTP streams.
-Z, --zerocopy
Use a "zero copy" method of sending data, such as sendfile(2),
instead of the usual write(2).
-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, --congestion algo
Set the congestion control algorithm (Linux and FreeBSD only).
An older --linux-congestion synonym for this flag is accepted but
is deprecated.
--get-server-output
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.
--username username
username to use for authentication to the iperf server (if built
with OpenSSL support). The password will be prompted for
interactively when the test is run.
--rsa-public-key-path file
path to the RSA public key used to encrypt authentication
credentials (if built with OpenSSL support)
EXAMPLES
Authentication - RSA Keypair
The authentication feature of requires an RSA public keypair. The
public key is used to encrypt the authentication token containing the
user credentials, while the private key is used to decrypt the
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authentication token. An example of a set of UNIX/Linux commands to
generate correct keypair follows:
> openssl genrsa -des3 -out private.pem 2048
> openssl rsa -in private.pem -outform PEM -pubout -out
public.pem
> openssl rsa -in private.pem -out private_not_protected.pem
-outform PEM
After these commands, the public key will be contained in the file
public.pem and the private key will be contained in the file
private_not_protected.pem.
Authentication - Authorized users configuration file
A simple plaintext file must be provided to the iperf3 server in order
to specify the authorized user credentials. The file is a simple list
of comma-separated pairs of a username and a corresponding password
hash. The password hash is a SHA256 hash of the string
"{$user}$password". The file can also contain commented lines
(starting with the # character). An example of commands to generate
the password hash on a UNIX/Linux system is given below:
> S_USER=mario S_PASSWD=rossi
> echo -n "{$S_USER}$S_PASSWD" | sha256sum | awk '{ print $1 }'
An example of a password file (with an entry corresponding to the
above username and password) is given below:
> cat credentials.csv
# file format: username,sha256
mario,bf7a49a846d44b454a5d11e7acfaf13d138bbe0b7483aa3e050879700572709b
AUTHORS
A list of the contributors to iperf3 can be found within the
documentation located at
http://software.es.net/iperf/dev.html#authors.
SEE ALSO
libiperf(3), http://software.es.net/iperf
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