1IPERF3(1) User Manuals IPERF3(1)
2
6 iperf3 - perform network throughput tests
7
9 iperf3 -s [ options ]
10 iperf3 -c server [ options ]
11
14 iperf3 is a tool for performing network throughput measurements. It
15 can test TCP, UDP, or SCTP throughput. To perform an iperf3 test the
16 user must establish both a server and a client.
17 The iperf3 executable contains both client and server functionality.
19 An iperf3 server can be started using either of the -s or --server com‐
20 mand-line parameters, for example:
21 iperf3 -s
23 iperf3 --server
25 Note that many iperf3 parameters have both short (-s) and long
27 (--server) forms. In this section we will generally use the short form
28 of command-line flags, unless only the long form of a flag is avail‐
29 able.
30 By default, the iperf3 server listens on TCP port 5201 for connections
32 from an iperf3 client. A custom port can be specified by using the -p
33 flag, for example:
34 iperf3 -s -p 5002
36 After the server is started, it will listen for connections from iperf3
38 clients (in other words, the iperf3 program run in client mode). The
39 client mode can be started using the -c command-line option, which also
40 requires a host to which iperf3 should connect. The host can by speci‐
41 fied by hostname, IPv4 literal, or IPv6 literal:
42 iperf3 -c iperf3.example.com
44 iperf3 -c 192.0.2.1
46 iperf3 -c 2001:db8::1
48 If the iperf3 server is running on a non-default TCP port, that port
50 number needs to be specified on the client as well:
51 iperf3 -c iperf3.example.com -p 5002
53 The initial TCP connection is used to exchange test parameters, control
55 the start and end of the test, and to exchange test results. This is
56 sometimes referred to as the "control connection". The actual test
57 data is sent over a separate TCP connection, as a separate flow of UDP
58 packets, or as an independent SCTP connection, depending on what proto‐
59 col was specified by the client.
60 Normally, the test data is sent from the client to the server, and mea‐
62 sures the upload speed of the client. Measuring the download speed
63 from the server can be done by specifying the -R flag on the client.
64 This causes data to be sent from the server to the client.
65 iperf3 -c iperf3.example.com -p 5202 -R
67 Results are displayed on both the client and server. There will be at
69 least one line of output per measurement interval (by default a mea‐
70 surement interval lasts for one second, but this can be changed by the
71 -i option). Each line of output includes (at least) the time since the
72 start of the test, amount of data transferred during the interval, and
73 the average bitrate over that interval. Note that the values for each
74 measurement interval are taken from the point of view of the endpoint
75 process emitting that output (in other words, the output on the client
76 shows the measurement interval data for the client.
77 At the end of the test is a set of statistics that shows (at least as
79 much as possible) a summary of the test as seen by both the sender and
80 the receiver, with lines tagged accordingly. Recall that by default
81 the client is the sender and the server is the receiver, although as
82 indicated above, use of the -R flag will reverse these roles.
83 The client can be made to retrieve the server-side output for a given
85 test by specifying the --get-server-output flag.
86 Either the client or the server can produce its output in a JSON struc‐
88 ture, useful for integration with other programs, by passing it the -J
89 flag. Because the contents of the JSON structure are only competely
90 known after the test has finished, no JSON output will be emitted until
91 the end of the test.
92 iperf3 has a (overly) large set of command-line options that can be
94 used to set the parameters of a test. They are given in the "GENERAL
95 OPTIONS" section of the manual page below, as well as summarized in
96 iperf3's help output, which can be viewed by running iperf3 with the -h
97 flag.
98
100 -p, --port n
101 set server port to listen on/connect to to n (default 5201)
102 -f, --format
104 [kmgtKMGT] format to report: Kbits/Mbits/Gbits/Tbits
105 -i, --interval n
107 pause n seconds between periodic throughput reports; default is
108 1, use 0 to disable
109 -F, --file name
111 Use a file as the source (on the sender) or sink (on the
112 receiver) of data, rather than just generating random data or
113 throwing it away. This feature is used for finding whether or
114 not the storage subsystem is the bottleneck for file transfers.
115 It does not turn iperf3 into a file transfer tool. The length,
116 attributes, and in some cases contents of the received file may
117 not match those of the original file.
118 -A, --affinity n/n,m
120 Set the CPU affinity, if possible (Linux, FreeBSD, and Windows
121 only). On both the client and server you can set the local
122 affinity by using the n form of this argument (where n is a CPU
123 number). In addition, on the client side you can override the
124 server's affinity for just that one test, using the n,m form of
125 argument. Note that when using this feature, a process will
126 only be bound to a single CPU (as opposed to a set containing
127 potentialy multiple CPUs).
128 -B, --bind host
130 bind to the specific interface associated with address host. If
131 the host has multiple interfaces, it will use the first inter‐
132 face by default.
133 -V, --verbose
135 give more detailed output
136 -J, --json
138 output in JSON format
139 --logfile file
141 send output to a log file.
142 --forceflush
144 force flushing output at every interval. Used to avoid buffer‐
145 ing when sending output to pipe.
146 -d, --debug
148 emit debugging output. Primarily (perhaps exclusively) of use
149 to developers.
150 -v, --version
152 show version information and quit
153 -h, --help
155 show a help synopsis
156
159 -s, --server
160 run in server mode
161 -D, --daemon
163 run the server in background as a daemon
164 -I, --pidfile file
166 write a file with the process ID, most useful when running as a
167 daemon.
168 -1, --one-off
170 handle one client connection, then exit.
171 --rsa-private-key-path file
173 path to the RSA private key (not password-protected) used to
174 decrypt authentication credentials from the client (if built
175 with OpenSSL support).
176 --authorized-users-path file
178 path to the configuration file containing authorized users cre‐
179 dentials to run iperf tests (if built with OpenSSL support).
180 The file is a comma separated list of usernames and password
181 hashes; more information on the structure of the file can be
182 found in the EXAMPLES section.
183
185 -c, --client host
186 run in client mode, connecting to the specified server. By
187 default, a test consists of sending data from the client to the
188 server, unless the -R flag is specified.
189 --sctp use SCTP rather than TCP (FreeBSD and Linux)
191 -u, --udp
193 use UDP rather than TCP
194 --connect-timeout n
196 set timeout for establishing the initial control connection to
197 the server, in milliseconds. The default behavior is the oper‐
198 ating system's timeout for TCP connection establishment. Pro‐
199 viding a shorter value may speed up detection of a down iperf3
200 server.
201 -b, --bitrate n[KM]
203 set target bitrate to n bits/sec (default 1 Mbit/sec for UDP,
204 unlimited for TCP/SCTP). If there are multiple streams (-P
205 flag), the throughput limit is applied separately to each
206 stream. You can also add a '/' and a number to the bitrate
207 specifier. This is called "burst mode". It will send the given
208 number of packets without pausing, even if that temporarily
209 exceeds the specified throughput limit. Setting the target
210 bitrate to 0 will disable bitrate limits (particularly useful
211 for UDP tests). This throughput limit is implemented internally
212 inside iperf3, and is available on all platforms. Compare with
213 the --fq-rate flag. This option replaces the --bandwidth flag,
214 which is now deprecated but (at least for now) still accepted.
215 --pacing-timer n[KMG]
217 set pacing timer interval in microseconds (default 1000
218 microseconds, or 1 ms). This controls iperf3's internal pacing
219 timer for the -b/--bitrate option. The timer fires at the
220 interval set by this parameter. Smaller values of the pacing
221 timer parameter smooth out the traffic emitted by iperf3, but
222 potentially at the cost of performance due to more frequent
223 timer processing.
224 --fq-rate n[KM]
226 Set a rate to be used with fair-queueing based socket-level pac‐
227 ing, in bits per second. This pacing (if specified) will be in
228 addition to any pacing due to iperf3's internal throughput pac‐
229 ing (-b/--bitrate flag), and both can be specified for the same
230 test. Only available on platforms supporting the SO_MAX_PAC‐
231 ING_RATE socket option (currently only Linux). The default is
232 no fair-queueing based pacing.
233 --no-fq-socket-pacing
235 This option is deprecated and will be removed. It is equivalent
236 to specifying --fq-rate=0.
237 -t, --time n
239 time in seconds to transmit for (default 10 secs)
240 -n, --bytes n[KM]
242 number of bytes to transmit (instead of -t)
243 -k, --blockcount n[KM]
245 number of blocks (packets) to transmit (instead of -t or -n)
246 -l, --length n[KM]
248 length of buffer to read or write. For TCP tests, the default
249 value is 128KB. In the case of UDP, iperf3 tries to dynamically
250 determine a reasonable sending size based on the path MTU; if
251 that cannot be determined it uses 1460 bytes as a sending size.
252 For SCTP tests, the default size is 64KB.
253 --cport port
255 bind data streams to a specific client port (for TCP and UDP
256 only, default is to use an ephemeral port)
257 -P, --parallel n
259 number of parallel client streams to run. Note that iperf3 is
260 single threaded, so if you are CPU bound, this will not yield
261 higher throughput.
262 -R, --reverse
264 reverse the direction of a test, so that the server sends data
265 to the client
266 -w, --window n[KM]
268 window size / socket buffer size (this gets sent to the server
269 and used on that side too)
270 -M, --set-mss n
272 set TCP/SCTP maximum segment size (MTU - 40 bytes)
273 -N, --no-delay
275 set TCP/SCTP no delay, disabling Nagle's Algorithm
276 -4, --version4
278 only use IPv4
279 -6, --version6
281 only use IPv6
282 -S, --tos n
284 set the IP type of service. The usual prefixes for octal and hex
285 can be used, i.e. 52, 064 and 0x34 all specify the same value.
286 --dscp dscp
288 set the IP DSCP bits. Both numeric and symbolic values are
289 accepted. Numeric values can be specified in decimal, octal and
290 hex (see --tos above).
291 -L, --flowlabel n
293 set the IPv6 flow label (currently only supported on Linux)
294 -X, --xbind name
296 Bind SCTP associations to a specific subset of links using
297 sctp_bindx(3). The --B flag will be ignored if this flag is
298 specified. Normally SCTP will include the protocol addresses of
299 all active links on the local host when setting up an associa‐
300 tion. Specifying at least one --X name will disable this behav‐
301 iour. This flag must be specified for each link to be included
302 in the association, and is supported for both iperf servers and
303 clients (the latter are supported by passing the first --X argu‐
304 ment to bind(2)). Hostnames are accepted as arguments and are
305 resolved using getaddrinfo(3). If the --4 or --6 flags are
306 specified, names which do not resolve to addresses within the
307 specified protocol family will be ignored.
308 --nstreams n
310 Set number of SCTP streams.
311 -Z, --zerocopy
313 Use a "zero copy" method of sending data, such as sendfile(2),
314 instead of the usual write(2).
315 -O, --omit n
317 Omit the first n seconds of the test, to skip past the TCP slow-
318 start period.
319 -T, --title str
321 Prefix every output line with this string.
322 --extra-data str
324 Specify an extra data string field to be included in JSON out‐
325 put.
326 -C, --congestion algo
328 Set the congestion control algorithm (Linux and FreeBSD only).
329 An older --linux-congestion synonym for this flag is accepted
330 but is deprecated.
331 --get-server-output
333 Get the output from the server. The output format is determined
334 by the server (in particular, if the server was invoked with the
335 --json flag, the output will be in JSON format, otherwise it
336 will be in human-readable format). If the client is run with
337 --json, the server output is included in a JSON object; other‐
338 wise it is appended at the bottom of the human-readable output.
339 --repeating-payload
341 Use repeating pattern in payload, instead of random bytes. The
342 same payload is used in iperf2 (ASCII '0..9' repeating). It
343 might help to test and reveal problems in networking gear with
344 hardware compression (including some WiFi access points), where
345 iperf2 and iperf3 perform differently, just based on payload
346 entropy.
347 --username username
349 username to use for authentication to the iperf server (if built
350 with OpenSSL support). The password will be prompted for inter‐
351 actively when the test is run.
352 --rsa-public-key-path file
354 path to the RSA public key used to encrypt authentication cre‐
355 dentials (if built with OpenSSL support)
356
359 Authentication - RSA Keypair
360 The authentication feature of iperf3 requires an RSA public keypair.
361 The public key is used to encrypt the authentication token containing
362 the user credentials, while the private key is used to decrypt the
363 authentication token. An example of a set of UNIX/Linux commands to
364 generate correct keypair follows:
365 > openssl genrsa -des3 -out private.pem 2048
367 > openssl rsa -in private.pem -outform PEM -pubout -out public.pem
368 > openssl rsa -in private.pem -out private_not_protected.pem -out‐
369 form PEM
370 After these commands, the public key will be contained in the file pub‐
372 lic.pem and the private key will be contained in the file pri‐
373 vate_not_protected.pem.
374 Authentication - Authorized users configuration file
376 A simple plaintext file must be provided to the iperf3 server in order
377 to specify the authorized user credentials. The file is a simple list
378 of comma-separated pairs of a username and a corresponding password
379 hash. The password hash is a SHA256 hash of the string "{$user}$pass‐
380 word". The file can also contain commented lines (starting with the #
381 character). An example of commands to generate the password hash on a
382 UNIX/Linux system is given below:
383 > S_USER=mario S_PASSWD=rossi
385 > echo -n "{$S_USER}$S_PASSWD" | sha256sum | awk '{ print $1 }'
386 An example of a password file (with an entry corresponding to the above
388 username and password) is given below:
389 > cat credentials.csv
390 # file format: username,sha256
391 mario,bf7a49a846d44b454a5d11e7acfaf13d138bbe0b7483aa3e050879700572709b
392
396 A list of the contributors to iperf3 can be found within the documenta‐
397 tion located at https://software.es.net/iperf/dev.html#authors.
398
401 libiperf(3), https://software.es.net/iperf
402ESnet June 2018 IPERF3(1)