= Summary =
iperf3 is a tool for measuring achievable bandwidth on IP networks.
iperf3 is NOT backwards compatible with the original iperf.
Supported platforms:
= Building iperf3 =
== Prerequisites: ==
== Building ==
./configure; make; make install
(Note: If configure fails, try running ./bootstrap.sh first)
= Latest version =
To check out the most recent code, do: hg clone http://code.google.com/p/iperf/
= Bug Reports =
Before submitting a bug report, try checking out the latest version of the code, and confirm that its not already fixed. Then submit to: https://code.google.com/p/iperf/issues/list
For more information see: http://code.google.com/p/iperf/
= Changes from iperf 2.x =
New options:
-V, --verbose more detailed output than before -J, --json output in JSON format -Z, --zerocopy use a 'zero copy' sendfile() method of sending data -O, --omit N omit the first n seconds (to ignore slowstart) -T, --title str prefix every output line with this string -F, --file name xmit/recv the specified file -A, --affinity n/n,m set CPU affinity (Linux and FreeBSD only) -k, --blockcount #[KMG] number of blocks (packets) to transmit (instead of -t or -n) -L, --flowlabel set IPv6 flow label (Linux only)
Changed flags: -C, --linux-congestion set congestion control algorithm (Linux only) (-Z in iperf2.0)
Deprecated options:
Not planning to support these iperf2 flags. If you really miss these options, please submit a request in the issue tracker:
-d, --dualtest Do a bidirectional test simultaneously -r, --tradeoff Do a bidirectional test individually -T, --ttl time-to-live, for multicast (default 1) -x, --reportexclude [CDMSV] exclude C(connection) D(data) M(multicast) S(settings) V(server) reports -y, --reportstyle C report as a Comma-Separated Values
Also deprecated is the ability to set the options via environment variables.
For sample command line usage, see:
http://fasterdata.es.net/performance-testing/network-troubleshooting-tools/iperf-and-iperf3/
Using the default options, iperf 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). iperf does also have flags for 'extreme best case' optimizations but they must be explicitly activated.
These flags include: -Z, --zerocopy use a 'zero copy' sendfile() method of sending data -A, --affinity n/n,m set CPU affinity
= Known Issues =
UDP performance: iperf2/iperf3 both only are only about 50% as fast as nuttcp in UDP mode. We are looking into this, but in the meantime, if you want to get UDP above 5Gbps, we recommend using nuttcp instead (http://www.nuttcp.net/)
Interval reports on high-loss networks: The way iperf3 is currently implemented, the sender write command will block until the entire block has been written. This means that it might take several seconds to send a full block if the network has high loss, and the interval reports will have widely varying interval times. We are trying to determine the best solution to this, but in the meantime, try using a smaller block size if you get strange interval reports. For example, try "-l 4K".
-Z flag on OSX sometimes hangs
On OpenBSD, the server seems to require a "-4" argument, implying that it can only be used with IPv4.