1IPERF3(1)                        User Manuals                        IPERF3(1)
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NAME

6       iperf3 - perform network throughput tests
7

SYNOPSIS

9       iperf3 -s [ options ]
10       iperf3 -c server [ options ]
11
12

DESCRIPTION

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
18       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
22              iperf3 -s
23
24              iperf3 --server
25
26       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
31       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
35              iperf3 -s -p 5002
36
37       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
43              iperf3 -c iperf3.example.com
44
45              iperf3 -c 192.0.2.1
46
47              iperf3 -c 2001:db8::1
48
49       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
52              iperf3 -c iperf3.example.com -p 5002
53
54       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
61       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
66              iperf3 -c iperf3.example.com -p 5202 -R
67
68       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
78       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
84       The  client  can be made to retrieve the server-side output for a given
85       test by specifying the --get-server-output flag.
86
87       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
93       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

GENERAL OPTIONS

100       -p, --port n
101              set server port to listen on/connect to to n (default 5201)
102
103       -f, --format
104              [kmgtKMGT]   format to report: Kbits/Mbits/Gbits/Tbits
105
106       -i, --interval n
107              pause n seconds between periodic throughput reports; default  is
108              1, use 0 to disable
109
110       -I, --pidfile file
111              write  a file with the process ID, most useful when running as a
112              daemon.
113
114       -F, --file name
115              Use a file as the source (on the sender) or  sink  (on  the  re‐
116              ceiver)  of  data,  rather  than  just generating random data or
117              throwing it away.  This feature is used for finding  whether  or
118              not  the storage subsystem is the bottleneck for file transfers.
119              It does not turn iperf3 into a file transfer tool.  The  length,
120              attributes,  and in some cases contents of the received file may
121              not match those of the original file.
122
123       -A, --affinity n/n,m
124              Set the CPU affinity, if possible (Linux, FreeBSD,  and  Windows
125              only).   On  both  the  client  and server you can set the local
126              affinity by using the n form of this argument (where n is a  CPU
127              number).   In  addition, on the client side you can override the
128              server's affinity for just that one test, using the n,m form  of
129              argument.   Note  that  when  using this feature, a process will
130              only be bound to a single CPU (as opposed to  a  set  containing
131              potentialy multiple CPUs).
132
133       -B, --bind host
134              bind  to  the  specific  interface associated with address host.
135              --bind-dev dev.ft R bind to  the  specified  network  interface.
136              This  option  uses SO_BINDTODEVICE, and may require root permis‐
137              sions.  (Available on Linux and possibly other systems.)
138
139       -V, --verbose
140              give more detailed output
141
142       -J, --json
143              output in JSON format
144
145       --logfile file
146              send output to a log file.
147
148       --forceflush
149              force flushing output at every interval.  Used to avoid  buffer‐
150              ing when sending output to pipe.
151
152       --timestamps[=format]
153              prepend  a  timestamp  at the start of each output line.  By de‐
154              fault, timestamps have the format emitted by ctime(1).   Option‐
155              ally, = followed by a format specification can be passed to cus‐
156              tomize the timestamps, see strftime(3).  If this optional format
157              is  given, the = must immediately follow the --timestamps option
158              with no whitespace intervening.
159
160       --rcv-timeout #
161              set idle timeout for receiving data during active tests. The re‐
162              ceiver  will  halt a test if no data is received from the sender
163              for this number of ms (default to 12000 ms, or 2 minutes).
164
165       -d, --debug
166              emit debugging output.  Primarily (perhaps exclusively)  of  use
167              to developers.
168
169       -v, --version
170              show version information and quit
171
172       -h, --help
173              show a help synopsis
174
175

SERVER SPECIFIC OPTIONS

177       -s, --server
178              run in server mode
179
180       -D, --daemon
181              run the server in background as a daemon
182
183       -1, --one-off
184              handle one client connection, then exit.
185
186       --server-bitrate-limit n[KMGT]
187              set a limit on the server side, which will cause a test to abort
188              if the client specifies a test of more than n bits  per  second,
189              or if the average data sent or received by the client (including
190              all data streams) is greater than n bits per  second.   The  de‐
191              fault  limit is zero, which implies no limit.  The interval over
192              which to average the data rate is 5 seconds by default, but  can
193              be  specified by adding a '/' and a number to the bitrate speci‐
194              fier.
195
196       --rsa-private-key-path file
197              path to the RSA private key (not password-protected) used to de‐
198              crypt  authentication credentials from the client (if built with
199              OpenSSL support).
200
201       --authorized-users-path file
202              path to the configuration file containing authorized users  cre‐
203              dentials  to  run  iperf  tests (if built with OpenSSL support).
204              The file is a comma separated list  of  usernames  and  password
205              hashes;  more  information  on  the structure of the file can be
206              found in the EXAMPLES section.
207
208       --time-skew-thresholdsecond seconds
209              time skew threshold (in seconds) between the server  and  client
210              during the authentication process.
211

CLIENT SPECIFIC OPTIONS

213       -c, --client host
214              run  in client mode, connecting to the specified server.  By de‐
215              fault, a test consists of sending data from the  client  to  the
216              server, unless the -R flag is specified.
217
218       --sctp use SCTP rather than TCP (FreeBSD and Linux)
219
220       -u, --udp
221              use UDP rather than TCP
222
223       --connect-timeout n
224              set  timeout  for establishing the initial control connection to
225              the server, in milliseconds.  The default behavior is the  oper‐
226              ating  system's  timeout for TCP connection establishment.  Pro‐
227              viding a shorter value may speed up detection of a  down  iperf3
228              server.
229
230       -b, --bitrate n[KMGT]
231              set  target  bitrate  to n bits/sec (default 1 Mbit/sec for UDP,
232              unlimited for TCP/SCTP).  If  there  are  multiple  streams  (-P
233              flag),  the  throughput  limit  is  applied  separately  to each
234              stream.  You can also add a '/' and  a  number  to  the  bitrate
235              specifier.  This is called "burst mode".  It will send the given
236              number of packets without pausing, even if that temporarily  ex‐
237              ceeds  the  specified  throughput limit.  Setting the target bi‐
238              trate to 0 will disable bitrate limits (particularly useful  for
239              UDP tests).  This throughput limit is implemented internally in‐
240              side iperf3, and is available on all  platforms.   Compare  with
241              the  --fq-rate flag.  This option replaces the --bandwidth flag,
242              which is now deprecated but (at least for now) still accepted.
243
244       --pacing-timer n[KMGT]
245              set pacing timer interval  in  microseconds  (default  1000  mi‐
246              croseconds,  or  1  ms).  This controls iperf3's internal pacing
247              timer for the -b/--bitrate option.  The timer fires at  the  in‐
248              terval  set  by  this  parameter.   Smaller values of the pacing
249              timer parameter smooth out the traffic emitted  by  iperf3,  but
250              potentially  at  the  cost  of  performance due to more frequent
251              timer processing.
252
253       --fq-rate n[KMGT]
254              Set a rate to be used with fair-queueing based socket-level pac‐
255              ing,  in bits per second.  This pacing (if specified) will be in
256              addition to any pacing due to iperf3's internal throughput  pac‐
257              ing  (-b/--bitrate flag), and both can be specified for the same
258              test.  Only available on platforms  supporting  the  SO_MAX_PAC‐
259              ING_RATE  socket  option (currently only Linux).  The default is
260              no fair-queueing based pacing.
261
262       --no-fq-socket-pacing
263              This option is deprecated and will be removed.  It is equivalent
264              to specifying --fq-rate=0.
265
266       -t, --time n
267              time in seconds to transmit for (default 10 secs)
268
269       -n, --bytes n[KMGT]
270              number of bytes to transmit (instead of -t)
271
272       -k, --blockcount n[KMGT]
273              number of blocks (packets) to transmit (instead of -t or -n)
274
275       -l, --length n[KMGT]
276              length  of  buffer to read or write.  For TCP tests, the default
277              value is 128KB.  In the case of UDP, iperf3 tries to dynamically
278              determine  a  reasonable  sending size based on the path MTU; if
279              that cannot be determined it uses 1460 bytes as a sending  size.
280              For SCTP tests, the default size is 64KB.
281
282       --cport port
283              bind  data  streams  to  a specific client port (for TCP and UDP
284              only, default is to use an ephemeral port)
285
286       -P, --parallel n
287              number of parallel client streams to run. Note  that  iperf3  is
288              single  threaded,  so  if you are CPU bound, this will not yield
289              higher throughput.
290
291       -R, --reverse
292              reverse the direction of a test, so that the server  sends  data
293              to the client
294
295       --bidir
296              test  in  both  directions  (normal  and reverse), with both the
297              client and server sending and receiving data simultaneously
298
299       -w, --window n[KMGT]
300              window size / socket buffer size (this gets sent to  the  server
301              and used on that side too)
302
303       -M, --set-mss n
304              set TCP/SCTP maximum segment size (MTU - 40 bytes)
305
306       -N, --no-delay
307              set TCP/SCTP no delay, disabling Nagle's Algorithm
308
309       -4, --version4
310              only use IPv4
311
312       -6, --version6
313              only use IPv6
314
315       -S, --tos n
316              set the IP type of service. The usual prefixes for octal and hex
317              can be used, i.e. 52, 064 and 0x34 all specify the same value.
318
319       --dscp dscp
320              set the IP DSCP bits.  Both numeric and symbolic values are  ac‐
321              cepted.  Numeric  values  can be specified in decimal, octal and
322              hex (see --tos above).
323
324       -L, --flowlabel n
325              set the IPv6 flow label (currently only supported on Linux)
326
327       -X, --xbind name
328              Bind SCTP associations to  a  specific  subset  of  links  using
329              sctp_bindx(3).   The  --B  flag  will be ignored if this flag is
330              specified.  Normally SCTP will include the protocol addresses of
331              all  active  links on the local host when setting up an associa‐
332              tion. Specifying at least one --X name will disable this  behav‐
333              iour.   This flag must be specified for each link to be included
334              in the association, and is supported for both iperf servers  and
335              clients (the latter are supported by passing the first --X argu‐
336              ment to bind(2)).  Hostnames are accepted as arguments  and  are
337              resolved  using  getaddrinfo(3).   If  the  --4 or --6 flags are
338              specified, names which do not resolve to  addresses  within  the
339              specified protocol family will be ignored.
340
341       --nstreams n
342              Set number of SCTP streams.
343
344       -Z, --zerocopy
345              Use  a  "zero copy" method of sending data, such as sendfile(2),
346              instead of the usual write(2).
347
348       -O, --omit n
349              Omit the first n seconds of the test, to skip past the TCP slow-
350              start period.
351
352       -T, --title str
353              Prefix every output line with this string.
354
355       --extra-data str
356              Specify  an  extra data string field to be included in JSON out‐
357              put.
358
359       -C, --congestion algo
360              Set the congestion control algorithm (Linux and  FreeBSD  only).
361              An  older  --linux-congestion  synonym for this flag is accepted
362              but is deprecated.
363
364       --get-server-output
365              Get the output from the server.  The output format is determined
366              by the server (in particular, if the server was invoked with the
367              --json flag, the output will be in  JSON  format,  otherwise  it
368              will  be  in  human-readable format).  If the client is run with
369              --json, the server output is included in a JSON  object;  other‐
370              wise it is appended at the bottom of the human-readable output.
371
372       --udp-counters-64bit
373              Use 64-bit counters in UDP test packets.  The use of this option
374              can help prevent counter overflows during long  or  high-bitrate
375              UDP  tests.   Both client and server need to be running at least
376              version 3.1 for this option to work.  It may become the  default
377              behavior at some point in the future.
378
379       --repeating-payload
380              Use  repeating pattern in payload, instead of random bytes.  The
381              same payload is used in iperf2  (ASCII  '0..9'  repeating).   It
382              might  help  to test and reveal problems in networking gear with
383              hardware compression (including some WiFi access points),  where
384              iperf2 and iperf3 perform differently, just based on payload en‐
385              tropy.
386
387       --dont-fragment
388              Set the IPv4 Don't Fragment (DF) bit on outgoing packets.   Only
389              applicable to tests doing UDP over IPv4.
390
391       --username username
392              username to use for authentication to the iperf server (if built
393              with OpenSSL support).  The password will be prompted for inter‐
394              actively  when  the  test is run.  Note, the password to use can
395              also be specified via the IPERF3_PASSWORD environment  variable.
396              If  this  variable  is  present,  the  password  prompt  will be
397              skipped.
398
399       --rsa-public-key-path file
400              path to the RSA public key used to encrypt  authentication  cre‐
401              dentials (if built with OpenSSL support)
402
403

EXAMPLES

405   Authentication - RSA Keypair
406       The  authentication  feature  of iperf3 requires an RSA public keypair.
407       The public key is used to encrypt the authentication  token  containing
408       the  user credentials, while the private key is used to decrypt the au‐
409       thentication token.  The private key must be in PEM  format  and  addi‐
410       tionally  must  not have a password set.  The public key must be in PEM
411       format and use SubjectPrefixKeyInfo encoding.  An example of a  set  of
412       UNIX/Linux  commands  using OpenSSL to generate a correctly-formed key‐
413       pair follows:
414
415            > openssl genrsa -des3 -out private.pem 2048
416            > openssl rsa -in private.pem -outform PEM -pubout -out public.pem
417            > openssl rsa -in private.pem -out private_not_protected.pem -out‐
418            form PEM
419
420       After these commands, the public key will be contained in the file pub‐
421       lic.pem and the  private  key  will  be  contained  in  the  file  pri‐
422       vate_not_protected.pem.
423
424   Authentication - Authorized users configuration file
425       A  simple plaintext file must be provided to the iperf3 server in order
426       to specify the authorized user credentials.  The file is a simple  list
427       of  comma-separated  pairs  of  a username and a corresponding password
428       hash.  The password hash is a SHA256 hash of the string  "{$user}$pass‐
429       word".   The file can also contain commented lines (starting with the #
430       character).  An example of commands to generate the password hash on  a
431       UNIX/Linux system is given below:
432
433            > S_USER=mario S_PASSWD=rossi
434            > echo -n "{$S_USER}$S_PASSWD" | sha256sum | awk '{ print $1 }'
435
436       An example of a password file (with an entry corresponding to the above
437       username and password) is given below:
438            > cat credentials.csv
439            # file format: username,sha256
440            mario,bf7a49a846d44b454a5d11e7ac‐
441            faf13d138bbe0b7483aa3e050879700572709b
442
443
444

AUTHORS

446       A list of the contributors to iperf3 can be found within the documenta‐
447       tion located at https://software.es.net/iperf/dev.html#authors.
448
449

SEE ALSO

451       libiperf(3), https://software.es.net/iperf
452
453
454
455ESnet                            February 2021                       IPERF3(1)
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