1IPERF3(1) User Manuals IPERF3(1)
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6 iperf3 - perform network throughput tests
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9 iperf3 -s [ options ]
10 iperf3 -c server [ options ]
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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 re‐
112 ceiver) 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.
131 -V, --verbose
133 give more detailed output
134 -J, --json
136 output in JSON format
137 --logfile file
139 send output to a log file.
140 --forceflush
142 force flushing output at every interval. Used to avoid buffer‐
143 ing when sending output to pipe.
144 --timestamps [format]
146 prepend a timestamp at the start of each output line. By de‐
147 fault, timestamps have the format emitted by ctime(1). Option‐
148 ally, a format specification can be passed to customize the
149 timestamps, see strftime(3).
150 -d, --debug
152 emit debugging output. Primarily (perhaps exclusively) of use
153 to developers.
154 -v, --version
156 show version information and quit
157 -h, --help
159 show a help synopsis
160
163 -s, --server
164 run in server mode
165 -D, --daemon
167 run the server in background as a daemon
168 -I, --pidfile file
170 write a file with the process ID, most useful when running as a
171 daemon.
172 -1, --one-off
174 handle one client connection, then exit.
175 --server-bitrate-limit n[KMGT]
177 set a limit on the server side, which will cause a test to abort
178 if the client specifies a test of more than n bits per second,
179 or if the average data sent or received by the client (including
180 all data streams) is greater than n bits per second. The de‐
181 fault limit is zero, which implies no limit. The interval over
182 which to average the data rate is 5 seconds by default, but can
183 be specified by adding a '/' and a number to the bitrate speci‐
184 fier.
185 --rsa-private-key-path file
187 path to the RSA private key (not password-protected) used to de‐
188 crypt authentication credentials from the client (if built with
189 OpenSSL support).
190 --authorized-users-path file
192 path to the configuration file containing authorized users cre‐
193 dentials to run iperf tests (if built with OpenSSL support).
194 The file is a comma separated list of usernames and password
195 hashes; more information on the structure of the file can be
196 found in the EXAMPLES section.
197
199 -c, --client host
200 run in client mode, connecting to the specified server. By de‐
201 fault, a test consists of sending data from the client to the
202 server, unless the -R flag is specified.
203 --sctp use SCTP rather than TCP (FreeBSD and Linux)
205 -u, --udp
207 use UDP rather than TCP
208 --connect-timeout n
210 set timeout for establishing the initial control connection to
211 the server, in milliseconds. The default behavior is the oper‐
212 ating system's timeout for TCP connection establishment. Pro‐
213 viding a shorter value may speed up detection of a down iperf3
214 server.
215 -b, --bitrate n[KMGT]
217 set target bitrate to n bits/sec (default 1 Mbit/sec for UDP,
218 unlimited for TCP/SCTP). If there are multiple streams (-P
219 flag), the throughput limit is applied separately to each
220 stream. You can also add a '/' and a number to the bitrate
221 specifier. This is called "burst mode". It will send the given
222 number of packets without pausing, even if that temporarily ex‐
223 ceeds the specified throughput limit. Setting the target bi‐
224 trate to 0 will disable bitrate limits (particularly useful for
225 UDP tests). This throughput limit is implemented internally in‐
226 side iperf3, and is available on all platforms. Compare with
227 the --fq-rate flag. This option replaces the --bandwidth flag,
228 which is now deprecated but (at least for now) still accepted.
229 --pacing-timer n[KMGT]
231 set pacing timer interval in microseconds (default 1000 mi‐
232 croseconds, or 1 ms). This controls iperf3's internal pacing
233 timer for the -b/--bitrate option. The timer fires at the in‐
234 terval set by this parameter. Smaller values of the pacing
235 timer parameter smooth out the traffic emitted by iperf3, but
236 potentially at the cost of performance due to more frequent
237 timer processing.
238 --fq-rate n[KMGT]
240 Set a rate to be used with fair-queueing based socket-level pac‐
241 ing, in bits per second. This pacing (if specified) will be in
242 addition to any pacing due to iperf3's internal throughput pac‐
243 ing (-b/--bitrate flag), and both can be specified for the same
244 test. Only available on platforms supporting the SO_MAX_PAC‐
245 ING_RATE socket option (currently only Linux). The default is
246 no fair-queueing based pacing.
247 --no-fq-socket-pacing
249 This option is deprecated and will be removed. It is equivalent
250 to specifying --fq-rate=0.
251 -t, --time n
253 time in seconds to transmit for (default 10 secs)
254 -n, --bytes n[KMGT]
256 number of bytes to transmit (instead of -t)
257 -k, --blockcount n[KMGT]
259 number of blocks (packets) to transmit (instead of -t or -n)
260 -l, --length n[KMGT]
262 length of buffer to read or write. For TCP tests, the default
263 value is 128KB. In the case of UDP, iperf3 tries to dynamically
264 determine a reasonable sending size based on the path MTU; if
265 that cannot be determined it uses 1460 bytes as a sending size.
266 For SCTP tests, the default size is 64KB.
267 --cport port
269 bind data streams to a specific client port (for TCP and UDP
270 only, default is to use an ephemeral port)
271 -P, --parallel n
273 number of parallel client streams to run. Note that iperf3 is
274 single threaded, so if you are CPU bound, this will not yield
275 higher throughput.
276 -R, --reverse
278 reverse the direction of a test, so that the server sends data
279 to the client
280 --bidir
282 test in both directions (normal and reverse), with both the
283 client and server sending and receiving data simultaneously
284 -w, --window n[KMGT]
286 window size / socket buffer size (this gets sent to the server
287 and used on that side too)
288 -M, --set-mss n
290 set TCP/SCTP maximum segment size (MTU - 40 bytes)
291 -N, --no-delay
293 set TCP/SCTP no delay, disabling Nagle's Algorithm
294 -4, --version4
296 only use IPv4
297 -6, --version6
299 only use IPv6
300 -S, --tos n
302 set the IP type of service. The usual prefixes for octal and hex
303 can be used, i.e. 52, 064 and 0x34 all specify the same value.
304 --dscp dscp
306 set the IP DSCP bits. Both numeric and symbolic values are ac‐
307 cepted. Numeric values can be specified in decimal, octal and
308 hex (see --tos above).
309 -L, --flowlabel n
311 set the IPv6 flow label (currently only supported on Linux)
312 -X, --xbind name
314 Bind SCTP associations to a specific subset of links using
315 sctp_bindx(3). The --B flag will be ignored if this flag is
316 specified. Normally SCTP will include the protocol addresses of
317 all active links on the local host when setting up an associa‐
318 tion. Specifying at least one --X name will disable this behav‐
319 iour. This flag must be specified for each link to be included
320 in the association, and is supported for both iperf servers and
321 clients (the latter are supported by passing the first --X argu‐
322 ment to bind(2)). Hostnames are accepted as arguments and are
323 resolved using getaddrinfo(3). If the --4 or --6 flags are
324 specified, names which do not resolve to addresses within the
325 specified protocol family will be ignored.
326 --nstreams n
328 Set number of SCTP streams.
329 -Z, --zerocopy
331 Use a "zero copy" method of sending data, such as sendfile(2),
332 instead of the usual write(2).
333 -O, --omit n
335 Omit the first n seconds of the test, to skip past the TCP slow-
336 start period.
337 -T, --title str
339 Prefix every output line with this string.
340 --extra-data str
342 Specify an extra data string field to be included in JSON out‐
343 put.
344 -C, --congestion algo
346 Set the congestion control algorithm (Linux and FreeBSD only).
347 An older --linux-congestion synonym for this flag is accepted
348 but is deprecated.
349 --get-server-output
351 Get the output from the server. The output format is determined
352 by the server (in particular, if the server was invoked with the
353 --json flag, the output will be in JSON format, otherwise it
354 will be in human-readable format). If the client is run with
355 --json, the server output is included in a JSON object; other‐
356 wise it is appended at the bottom of the human-readable output.
357 --udp-counters-64bit
359 Use 64-bit counters in UDP test packets. The use of this option
360 can help prevent counter overflows during long or high-bitrate
361 UDP tests. Both client and server need to be running at least
362 version 3.1 for this option to work. It may become the default
363 behavior at some point in the future.
364 --repeating-payload
366 Use repeating pattern in payload, instead of random bytes. The
367 same payload is used in iperf2 (ASCII '0..9' repeating). It
368 might help to test and reveal problems in networking gear with
369 hardware compression (including some WiFi access points), where
370 iperf2 and iperf3 perform differently, just based on payload en‐
371 tropy.
372 --username username
374 username to use for authentication to the iperf server (if built
375 with OpenSSL support). The password will be prompted for inter‐
376 actively when the test is run. Note, the password to use can
377 also be specified via the IPERF3_PASSWORD environment variable.
378 If this variable is present, the password prompt will be
379 skipped.
380 --rsa-public-key-path file
382 path to the RSA public key used to encrypt authentication cre‐
383 dentials (if built with OpenSSL support)
384
387 Authentication - RSA Keypair
388 The authentication feature of iperf3 requires an RSA public keypair.
389 The public key is used to encrypt the authentication token containing
390 the user credentials, while the private key is used to decrypt the au‐
391 thentication token. An example of a set of UNIX/Linux commands to gen‐
392 erate correct keypair follows:
393 > openssl genrsa -des3 -out private.pem 2048
395 > openssl rsa -in private.pem -outform PEM -pubout -out public.pem
396 > openssl rsa -in private.pem -out private_not_protected.pem -out‐
397 form PEM
398 After these commands, the public key will be contained in the file pub‐
400 lic.pem and the private key will be contained in the file pri‐
401 vate_not_protected.pem.
402 Authentication - Authorized users configuration file
404 A simple plaintext file must be provided to the iperf3 server in order
405 to specify the authorized user credentials. The file is a simple list
406 of comma-separated pairs of a username and a corresponding password
407 hash. The password hash is a SHA256 hash of the string "{$user}$pass‐
408 word". The file can also contain commented lines (starting with the #
409 character). An example of commands to generate the password hash on a
410 UNIX/Linux system is given below:
411 > S_USER=mario S_PASSWD=rossi
413 > echo -n "{$S_USER}$S_PASSWD" | sha256sum | awk '{ print $1 }'
414 An example of a password file (with an entry corresponding to the above
416 username and password) is given below:
417 > cat credentials.csv
418 # file format: username,sha256
419 mario,bf7a49a846d44b454a5d11e7ac‐
420 faf13d138bbe0b7483aa3e050879700572709b
421
425 A list of the contributors to iperf3 can be found within the documenta‐
426 tion located at https://software.es.net/iperf/dev.html#authors.
427
430 libiperf(3), https://software.es.net/iperf
431ESnet July 2020 IPERF3(1)