iperf3 includes a manual page listing all of the command-line options. The manual page is the most up-to-date reference to the various flags and parameters.
For sample command line usage, see:
Using the default options, iperf3 is meant to show typical well
designed application performance. “Typical well designed application”
means avoiding artificial enhancements that work only for testing
splice()-ing the data to
/dev/null). iperf3 does
also have flags for “extreme best case” optimizations but they must be
explicitly activated. These flags include the
This section contains a plaintext rendering of the iperf3 manual page. It is presented here only for convenience; the authoritative iperf3 manual page is included in the source tree and installed along with the executable.
IPERF3(1) User Manuals IPERF3(1) 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 either TCP or UDP throughput. To perform an iperf3 test the user must establish both a server and a client. GENERAL OPTIONS -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 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 mul- tiple CPUs). -B, --bind host bind to a specific interface -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 buffer- ing when sending output to pipe. -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 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. CLIENT SPECIFIC OPTIONS -c, --client host run in client mode, connecting to the specified server --sctp use SCTP rather than TCP (FreeBSD and Linux) -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). This bandwidth limit is implemented internally inside iperf3, and is available on all platforms. Compare with the --fq-rate flag. --fq-rate n[KM] Set a rate to be used with fair-queueing based socket-level pac- ing, in bits per second. This pacing (if specified) will be in addition to any pacing due to iperf3's internal bandwidth pacing (-b 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 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 -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) -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' -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 associa- tion. Specifying at least one --X name will disable this behav- iour. This flag must be specified for each link to be included in the association, and is supported for both iperf servers and clients (the latter are supported by passing the first --X argu- ment 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; other- wise it is appended at the bottom of the human-readable output. AUTHORS A list of the contributors to iperf3 can be found within the documenta- tion located at http://software.es.net/iperf/dev.html#authors. SEE ALSO libiperf(3), http://software.es.net/iperf ESnet January 2017 IPERF3(1)
The iperf3 manual page will typically be installed in manual section 1.