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version 1.1, 2016/10/18 13:28:17	version 1.1.1.2, 2021/03/17 00:36:45
Line 7 Summary	Line 7 Summary
iperf is a tool for active measurements of the maximum achievable	iperf is a tool for active measurements of the maximum achievable
bandwidth on IP networks. It supports tuning of various parameters	bandwidth on IP networks. It supports tuning of various parameters
related to timing, protocols, and buffers. For each test it reports	related to timing, protocols, and buffers. For each test it reports
the bandwidth, loss, and other parameters.	the measured throughput / bitrate, loss, and other parameters.

This version, sometimes referred to as iperf3, is a redesign of an	This version, sometimes referred to as iperf3, is a redesign of an
original version developed at NLANR/DAST. iperf3 is a new	original version developed at NLANR/DAST. iperf3 is a new
implementation from scratch, with the goal of a smaller, simpler code	implementation from scratch, with the goal of a smaller, simpler code
base, and a library version of the functionality that can be used in	base, and a library version of the functionality that can be used in
other programs. iperf3 also a number of features found in other tools	other programs. iperf3 also has a number of features found in other tools
such as nuttcp and netperf, but were missing from the original iperf.	such as nuttcp and netperf, but were missing from the original iperf.
These include, for example, a zero-copy mode and optional JSON output.	These include, for example, a zero-copy mode and optional JSON output.
Note that iperf3 is not backwards compatible with the original iperf.	Note that iperf3 is not backwards compatible with the original iperf.

Primary development for iperf3 takes place on CentOS Linux, FreeBSD,	Primary development for iperf3 takes place on CentOS Linux, FreeBSD,
and MacOS X. At this time, these are the only officially supported	and macOS. At this time, these are the only officially supported
platforms, however there have been some reports of success with	platforms, however there have been some reports of success with
OpenBSD, NetBSD, Android, Solaris, and other Linux distributions.	OpenBSD, NetBSD, Android, Solaris, and other Linux distributions.

iperf3 is principally developed by ESnet / Lawrence Berkeley National	iperf3 is principally developed by ESnet / Lawrence Berkeley National
Laboratory. It is released under a three-clause BSD license.	Laboratory. It is released under a three-clause BSD license.

Note that at this point, ESnet plans to support iperf3 in "maintenance	For more information see: https://software.es.net/iperf
mode". At this point, there are no definite plans for further iperf3
releases, and ESnet will be providing a very limited amount of
resources for support and development, going forward. However, ESnet
could issue new iperf3 releases to deal with security issues or
high-impact bug fixes.

For more information see: http://software.es.net/iperf

Source code and issue tracker: https://github.com/esnet/iperf	Source code and issue tracker: https://github.com/esnet/iperf

Obtaining iperf3	Obtaining iperf3
Line 42 Obtaining iperf3	Line 35 Obtaining iperf3

Downloads of iperf3 are available at:	Downloads of iperf3 are available at:

http://downloads.es.net/pub/iperf/	https://downloads.es.net/pub/iperf/

To check out the most recent code, clone the git repository at:	To check out the most recent code, clone the git repository at:

Line 69 The manual page is the most up-to-date reference to th	Line 62 The manual page is the most up-to-date reference to th

For sample command line usage, see:	For sample command line usage, see:

http://fasterdata.es.net/performance-testing/network-troubleshooting-tools/iperf-and-iperf3/	https://fasterdata.es.net/performance-testing/network-troubleshooting-tools/iperf/

Using the default options, iperf is meant to show typical well	Using the default options, iperf is meant to show typical well
designed application performance. 'Typical well designed application'	designed application performance. "Typical well designed application"
means avoiding artificial enhancements that work only for testing	means avoiding artificial enhancements that work only for testing
(such as splice()'ing the data to /dev/null). iperf does also have	(such as splice()'ing the data to /dev/null). iperf does also have
flags for 'extreme best case' optimizations but they must be	flags for "extreme best case" optimizations, but they must be
explicitly activated.	explicitly activated.

These flags include:	These flags include:
Line 104 sensitive information.	Line 97 sensitive information.
If you have a question about usage or about the code, please do not	If you have a question about usage or about the code, please do not
submit an issue. Please use one of the mailing lists for that.	submit an issue. Please use one of the mailing lists for that.

Changes from iperf 2.x	Relation to iperf 2.x
----------------------	---------------------

New options:	Note that iperf2 is no longer being developed by its original
	maintainers. However, beginning in 2014, another developer began
	fixing bugs and enhancing functionality, and generating releases of
	iperf2. Both projects (as of late 2017) are currently being developed
	actively, but independently. The continuing iperf2 development
	project can be found at https://sourceforge.net/projects/iperf2/.

-V, --verbose more detailed output than before	iperf3 contains a number of options and functions not present in
-J, --json output in JSON format	iperf2. In addition, some flags are changed from their iperf2
-Z, --zerocopy use a 'zero copy' sendfile() method of sending data	counterparts:
-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)	-C, --linux-congestion set congestion control algorithm (Linux only)
(-Z in iperf2)	(-Z in iperf2)
	--bidir bidirectional testing mode
	(-d in iperf2)

	Some iperf2 options are not available in iperf3:

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	-r, --tradeoff Do a bidirectional test individually
-T, --ttl time-to-live, for multicast (default 1)	-T, --ttl time-to-live, for multicast (default 1)
-x, --reportexclude [CDMSV] exclude C(connection) D(data) M(multicast)	-x, --reportexclude [CDMSV] exclude C(connection) D(data) M(multicast)
S(settings) V(server) reports	S(settings) V(server) reports
-y, --reportstyle C report as a Comma-Separated Values	-y, --reportstyle C report as a Comma-Separated Values

Also deprecated is the ability to set the options via environment	Also removed is the ability to set the options via environment
variables.	variables.

Known Issues	Known Issues
------------	------------

* UDP performance: Some problems have been noticed with iperf3 on the	A set of known issues is maintained on the iperf3 Web pages:
ESnet 100G testbed at high UDP rates (above 10Gbps). The symptom is
that on any particular run of iperf3 the receiver reports a loss rate
of about 20%, regardless of the -b option used on the client side.
This problem appears not to be iperf3-specific, and may be due to the
placement of the iperf3 process on a CPU and its relation to the
inbound NIC. In some cases this problem can be mitigated by an
appropriate use of the CPU affinity (-A) option. (Issue #55)

* The -Z flag sometimes causes the iperf3 client to hang on OSX.	https://software.es.net/iperf/dev.html#known-issues
(Issue #129)

* When specifying the socket buffer size using the "-w" flag on Linux, Linux
doubles the value you pass in. (You can see this using iperf3's debug flag).
But then the CWND does not actually ramp up to the doubled value, but only
to about 75% of the doubled value. This appears to be by design.

* Although the "-w" flag is documented as setting the (TCP) window
size, it is also used to set the socket buffer size. This has been
shown to be helpful with high-bitrate UDP tests.

* On some platforms, it might be necessary to invoke "ldconfig"
manually after doing a "make install" before the iperf3 executable can
find its shared library. (Issue #153)

* The results printed on the server side at the end of a test do not
correctly reflect the client-side measurements. This is due to the
ordering of computing and transferring results between the client
and server. (Issue #293)

* The server could have a very short measurement reporting interval at
the end of a test (particularly a UDP test), containing few or no
packets. This issue is due to an artifact of timing between the
client and server. (Issue #278)

Links	Links
-----	-----

Line 194 responsibility for the content of these pages.	Line 149 responsibility for the content of these pages.
Copyright	Copyright
---------	---------

iperf, Copyright (c) 2014-2016, The Regents of the University of	iperf, Copyright (c) 2014-2020, The Regents of the University of
California, through Lawrence Berkeley National Laboratory (subject	California, through Lawrence Berkeley National Laboratory (subject
to receipt of any required approvals from the U.S. Dept. of	to receipt of any required approvals from the U.S. Dept. of
Energy). All rights reserved.	Energy). All rights reserved.

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