Invoking iperf3 =============== 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: http://fasterdata.es.net/performance-testing/network-troubleshooting-tools/iperf-and-iperf3/ 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 (such as ``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 ``-Z`` (``--zerocopy``) and ``-A`` (``--affinity``) options. iperf3 Manual Page ------------------ 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. :: IPERF(1) User Manuals IPERF(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. ‐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. 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. ‐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] TCP window size / socket buffer size (this gets sent to the server and used on that side too) ‐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 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, ‐‐linux‐congestion algo Set the congestion control algorithm (linux only). AUTHORS Iperf was originally written by Mark Gates and Alex Warshavsky. Man page and maintence by Jon Dugan . Other con‐ tributions from Ajay Tirumala, Jim Ferguson, Feng Qin, Kevin Gibbs, John Estabrook , Andrew Gallatin , Stephen Hemminger SEE ALSO libiperf(3), https://github.com/esnet/iperf ESnet February 2014 IPERF(1) The iperf3 manual page will typically be installed in manual section 1.