1 Invoking iperf3 2 =============== 3 4 iperf3 includes a manual page listing all of the command-line options. 5 The manual page is the most up-to-date reference to the various flags and parameters. 6 7 For sample command line usage, see: 8 9 https://fasterdata.es.net/performance-testing/network-troubleshooting-tools/iperf/ 10 11 Using the default options, iperf3 is meant to show typical well 12 designed application performance. "Typical well designed application" 13 means avoiding artificial enhancements that work only for testing 14 (such as ``splice()``-ing the data to ``/dev/null``). iperf3 does 15 also have flags for "extreme best case" optimizations but they must be 16 explicitly activated. These flags include the ``-Z`` (``--zerocopy``) 17 and ``-A`` (``--affinity``) options. 18 19 iperf3 Manual Page 20 ------------------ 21 22 This section contains a plaintext rendering of the iperf3 manual page. 23 It is presented here only for convenience; the text here might not 24 correspond to the current version of iperf3. The authoritative iperf3 25 manual page is included in the source tree and installed along with 26 the executable. 27 28 :: 29 30 IPERF3(1) User Manuals IPERF3(1) 31 32 33 34 NAME 35 iperf3 - perform network throughput tests 36 37 SYNOPSIS 38 iperf3 -s [ options ] 39 iperf3 -c server [ options ] 40 41 42 DESCRIPTION 43 iperf3 is a tool for performing network throughput measurements. It 44 can test TCP, UDP, or SCTP throughput. To perform an iperf3 test the 45 user must establish both a server and a client. 46 47 The iperf3 executable contains both client and server functionality. 48 An iperf3 server can be started using either of the -s or --server com- 49 mand-line parameters, for example: 50 51 iperf3 -s 52 53 iperf3 --server 54 55 Note that many iperf3 parameters have both short (-s) and long 56 (--server) forms. In this section we will generally use the short form 57 of command-line flags, unless only the long form of a flag is avail- 58 able. 59 60 By default, the iperf3 server listens on TCP port 5201 for connections 61 from an iperf3 client. A custom port can be specified by using the -p 62 flag, for example: 63 64 iperf3 -s -p 5002 65 66 After the server is started, it will listen for connections from iperf3 67 clients (in other words, the iperf3 program run in client mode). The 68 client mode can be started using the -c command-line option, which also 69 requires a host to which iperf3 should connect. The host can by speci- 70 fied by hostname, IPv4 literal, or IPv6 literal: 71 72 iperf3 -c iperf3.example.com 73 74 iperf3 -c 192.0.2.1 75 76 iperf3 -c 2001:db8::1 77 78 If the iperf3 server is running on a non-default TCP port, that port 79 number needs to be specified on the client as well: 80 81 iperf3 -c iperf3.example.com -p 5002 82 83 The initial TCP connection is used to exchange test parameters, control 84 the start and end of the test, and to exchange test results. This is 85 sometimes referred to as the "control connection". The actual test 86 data is sent over a separate TCP connection, as a separate flow of UDP 87 packets, or as an independent SCTP connection, depending on what proto- 88 col was specified by the client. 89 90 Normally, the test data is sent from the client to the server, and mea- 91 sures the upload speed of the client. Measuring the download speed 92 from the server can be done by specifying the -R flag on the client. 93 This causes data to be sent from the server to the client. 94 95 iperf3 -c iperf3.example.com -p 5202 -R 96 97 Results are displayed on both the client and server. There will be at 98 least one line of output per measurement interval (by default a mea- 99 surement interval lasts for one second, but this can be changed by the 100 -i option). Each line of output includes (at least) the time since the 101 start of the test, amount of data transferred during the interval, and 102 the average bitrate over that interval. Note that the values for each 103 measurement interval are taken from the point of view of the endpoint 104 process emitting that output (in other words, the output on the client 105 shows the measurement interval data for the client. 106 107 At the end of the test is a set of statistics that shows (at least as 108 much as possible) a summary of the test as seen by both the sender and 109 the receiver, with lines tagged accordingly. Recall that by default 110 the client is the sender and the server is the receiver, although as 111 indicated above, use of the -R flag will reverse these roles. 112 113 The client can be made to retrieve the server-side output for a given 114 test by specifying the --get-server-output flag. 115 116 Either the client or the server can produce its output in a JSON struc- 117 ture, useful for integration with other programs, by passing it the -J 118 flag. Because the contents of the JSON structure are only competely 119 known after the test has finished, no JSON output will be emitted until 120 the end of the test. 121 122 iperf3 has a (overly) large set of command-line options that can be 123 used to set the parameters of a test. They are given in the "GENERAL 124 OPTIONS" section of the manual page below, as well as summarized in 125 iperf3's help output, which can be viewed by running iperf3 with the -h 126 flag. 127 128 GENERAL OPTIONS 129 -p, --port n 130 set server port to listen on/connect to to n (default 5201) 131 132 -f, --format 133 [kmgtKMGT] format to report: Kbits/Mbits/Gbits/Tbits 134 135 -i, --interval n 136 pause n seconds between periodic throughput reports; default is 137 1, use 0 to disable 138 139 -F, --file name 140 Use a file as the source (on the sender) or sink (on the 141 receiver) of data, rather than just generating random data or 142 throwing it away. This feature is used for finding whether or 143 not the storage subsystem is the bottleneck for file transfers. 144 It does not turn iperf3 into a file transfer tool. The length, 145 attributes, and in some cases contents of the received file may 146 not match those of the original file. 147 148 -A, --affinity n/n,m 149 Set the CPU affinity, if possible (Linux, FreeBSD, and Windows 150 only). On both the client and server you can set the local 151 affinity by using the n form of this argument (where n is a CPU 152 number). In addition, on the client side you can override the 153 server's affinity for just that one test, using the n,m form of 154 argument. Note that when using this feature, a process will 155 only be bound to a single CPU (as opposed to a set containing 156 potentialy multiple CPUs). 157 158 -B, --bind host 159 bind to the specific interface associated with address host. If 160 the host has multiple interfaces, it will use the first inter- 161 face by default. 162 163 -V, --verbose 164 give more detailed output 165 166 -J, --json 167 output in JSON format 168 169 --logfile file 170 send output to a log file. 171 172 --forceflush 173 force flushing output at every interval. Used to avoid buffer- 174 ing when sending output to pipe. 175 176 -d, --debug 177 emit debugging output. Primarily (perhaps exclusively) of use 178 to developers. 179 180 -v, --version 181 show version information and quit 182 183 -h, --help 184 show a help synopsis 185 186 187 SERVER SPECIFIC OPTIONS 188 -s, --server 189 run in server mode 190 191 -D, --daemon 192 run the server in background as a daemon 193 194 -I, --pidfile file 195 write a file with the process ID, most useful when running as a 196 daemon. 197 198 -1, --one-off 199 handle one client connection, then exit. 200 201 --rsa-private-key-path file 202 path to the RSA private key (not password-protected) used to 203 decrypt authentication credentials from the client (if built 204 with OpenSSL support). 205 206 --authorized-users-path file 207 path to the configuration file containing authorized users cre- 208 dentials to run iperf tests (if built with OpenSSL support). 209 The file is a comma separated list of usernames and password 210 hashes; more information on the structure of the file can be 211 found in the EXAMPLES section. 212 213 CLIENT SPECIFIC OPTIONS 214 -c, --client host 215 run in client mode, connecting to the specified server. By 216 default, a test consists of sending data from the client to the 217 server, unless the -R flag is specified. 218 219 --sctp use SCTP rather than TCP (FreeBSD and Linux) 220 221 -u, --udp 222 use UDP rather than TCP 223 224 --connect-timeout n 225 set timeout for establishing the initial control connection to 226 the server, in milliseconds. The default behavior is the oper- 227 ating system's timeout for TCP connection establishment. Pro- 228 viding a shorter value may speed up detection of a down iperf3 229 server. 230 231 -b, --bitrate n[KM] 232 set target bitrate to n bits/sec (default 1 Mbit/sec for UDP, 233 unlimited for TCP/SCTP). If there are multiple streams (-P 234 flag), the throughput limit is applied separately to each 235 stream. You can also add a '/' and a number to the bitrate 236 specifier. This is called "burst mode". It will send the given 237 number of packets without pausing, even if that temporarily 238 exceeds the specified throughput limit. Setting the target 239 bitrate to 0 will disable bitrate limits (particularly useful 240 for UDP tests). This throughput limit is implemented internally 241 inside iperf3, and is available on all platforms. Compare with 242 the --fq-rate flag. This option replaces the --bandwidth flag, 243 which is now deprecated but (at least for now) still accepted. 244 245 --pacing-timer n[KMG] 246 set pacing timer interval in microseconds (default 1000 247 microseconds, or 1 ms). This controls iperf3's internal pacing 248 timer for the -b/--bitrate option. The timer fires at the 249 interval set by this parameter. Smaller values of the pacing 250 timer parameter smooth out the traffic emitted by iperf3, but 251 potentially at the cost of performance due to more frequent 252 timer processing. 253 254 --fq-rate n[KM] 255 Set a rate to be used with fair-queueing based socket-level pac- 256 ing, in bits per second. This pacing (if specified) will be in 257 addition to any pacing due to iperf3's internal throughput pac- 258 ing (-b/--bitrate flag), and both can be specified for the same 259 test. Only available on platforms supporting the SO_MAX_PAC- 260 ING_RATE socket option (currently only Linux). The default is 261 no fair-queueing based pacing. 262 263 --no-fq-socket-pacing 264 This option is deprecated and will be removed. It is equivalent 265 to specifying --fq-rate=0. 266 267 -t, --time n 268 time in seconds to transmit for (default 10 secs) 269 270 -n, --bytes n[KM] 271 number of bytes to transmit (instead of -t) 272 273 -k, --blockcount n[KM] 274 number of blocks (packets) to transmit (instead of -t or -n) 275 276 -l, --length n[KM] 277 length of buffer to read or write. For TCP tests, the default 278 value is 128KB. In the case of UDP, iperf3 tries to dynamically 279 determine a reasonable sending size based on the path MTU; if 280 that cannot be determined it uses 1460 bytes as a sending size. 281 For SCTP tests, the default size is 64KB. 282 283 --cport port 284 bind data streams to a specific client port (for TCP and UDP 285 only, default is to use an ephemeral port) 286 287 -P, --parallel n 288 number of parallel client streams to run. Note that iperf3 is 289 single threaded, so if you are CPU bound, this will not yield 290 higher throughput. 291 292 -R, --reverse 293 reverse the direction of a test, so that the server sends data 294 to the client 295 296 --bidir 297 bidirectional mode, server and client send and receive data. 298 299 -w, --window n[KM] 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 321 accepted. 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 --repeating-payload 373 Use repeating pattern in payload, instead of random bytes. The 374 same payload is used in iperf2 (ASCII '0..9' repeating). It 375 might help to test and reveal problems in networking gear with 376 hardware compression (including some WiFi access points), where 377 iperf2 and iperf3 perform differently, just based on payload 378 entropy. 379 380 --username username 381 username to use for authentication to the iperf server (if built 382 with OpenSSL support). The password will be prompted for inter- 383 actively when the test is run. Note, the password to use can 384 also be specified via the IPERF3_PASSWORD environment variable. 385 If this variable is present, the password prompt will be 386 skipped. 387 388 --rsa-public-key-path file 389 path to the RSA public key used to encrypt authentication cre- 390 dentials (if built with OpenSSL support) 391 392 393 EXAMPLES 394 Authentication - RSA Keypair 395 The authentication feature of iperf3 requires an RSA public keypair. 396 The public key is used to encrypt the authentication token containing 397 the user credentials, while the private key is used to decrypt the 398 authentication token. An example of a set of UNIX/Linux commands to 399 generate correct keypair follows: 400 401 > openssl genrsa -des3 -out private.pem 2048 402 > openssl rsa -in private.pem -outform PEM -pubout -out public.pem 403 > openssl rsa -in private.pem -out private_not_protected.pem -out- 404 form PEM 405 406 After these commands, the public key will be contained in the file pub- 407 lic.pem and the private key will be contained in the file pri- 408 vate_not_protected.pem. 409 410 Authentication - Authorized users configuration file 411 A simple plaintext file must be provided to the iperf3 server in order 412 to specify the authorized user credentials. The file is a simple list 413 of comma-separated pairs of a username and a corresponding password 414 hash. The password hash is a SHA256 hash of the string "{$user}$pass- 415 word". The file can also contain commented lines (starting with the # 416 character). An example of commands to generate the password hash on a 417 UNIX/Linux system is given below: 418 419 > S_USER=mario S_PASSWD=rossi 420 > echo -n "{$S_USER}$S_PASSWD" | sha256sum | awk '{ print $1 }' 421 422 An example of a password file (with an entry corresponding to the above 423 username and password) is given below: 424 > cat credentials.csv 425 # file format: username,sha256 426 mario,bf7a49a846d44b454a5d11e7acfaf13d138bbe0b7483aa3e050879700572709b 427 428 429 430 AUTHORS 431 A list of the contributors to iperf3 can be found within the documenta- 432 tion located at https://software.es.net/iperf/dev.html#authors. 433 434 435 SEE ALSO 436 libiperf(3), https://software.es.net/iperf 437 438 439 440 ESnet June 2018 IPERF3(1) 441 442 The iperf3 manual page will typically be installed in manual 443 section 1. 444 445
