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Network Speed Testing Using iperf3
iperf is a command line utility which provides info about bandwidth, network delays and datagram loss. It can test both TCP and UDP throughput speeds.
To perform an iperf test you establish both a server machine as one end-point, which discards the test traffic, and a client machine, which generates test traffic.
iperf must be installed on both machines. For Debian/Ubuntu:
(in this case we are installing version iperf3)
apt update
apt install iperf3 -y
Re Firewalling
You must open TCP port 5001 on the server machine.
Using Ubuntu/Debian Linux you can do:
ufw allow from 10.147.18.0/24 to 10.147.18.0/24 port 5001 proto tcp
On CentOS/RHEL/Fedora:
firewall-cmd –zone=public –add-port=5001/tcp –permanent
For the purpose of the test I simply briefly disabled fwall on gemini.
I found I only needed to temporarily disable ufw on gemini not on the client.
Or you can do:
root@gemini:/home/kevin# ufw allow 5201 Rule added Rule added (v6) root@gemini:/home/kevin#
You can also change the port by passing the -p option (e.g. in this case to open and use TCP port 2456):
iperf3 -s -p 2456
Then start an iperf server on the server machine using iperf3 server mode:
iperf3 -s
so we do:
root@gemini:/home/kevin# iperf3 -s ----------------------------------------------------------- Server listening on 5201 -----------------------------------------------------------
Next, start an iperf server on the client machine in iperf3 client mode:
iperf3 -c {ip-address-of-server}
iperf3 -c {ip-address-of-server} -p {tcp-port}
in our case, we want to test our VPN, so we enter the geminivpn IP, not the gemini external internet IP!
so we do:
iperf3 -c 10.147.18.185
the result:
root@gemini:/home/kevin# iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 10.147.18.65, port 49458 [ 5] local 10.147.18.185 port 5201 connected to 10.147.18.65 port 49460 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 953 KBytes 7.80 Mbits/sec [ 5] 1.00-2.00 sec 1.18 MBytes 9.87 Mbits/sec [ 5] 2.00-3.00 sec 971 KBytes 7.96 Mbits/sec [ 5] 3.00-4.00 sec 1.13 MBytes 9.48 Mbits/sec [ 5] 4.00-5.00 sec 1.15 MBytes 9.61 Mbits/sec [ 5] 5.00-6.00 sec 1014 KBytes 8.31 Mbits/sec [ 5] 6.00-7.00 sec 1.10 MBytes 9.25 Mbits/sec [ 5] 7.00-8.00 sec 1.14 MBytes 9.59 Mbits/sec [ 5] 8.00-9.00 sec 1.14 MBytes 9.54 Mbits/sec [ 5] 9.00-10.00 sec 1.06 MBytes 8.88 Mbits/sec [ 5] 10.00-10.03 sec 32.2 KBytes 8.91 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate [ 5] 0.00-10.03 sec 10.8 MBytes 9.03 Mbits/sec receiver ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- root@len:/home/kevin# iperf3 -c 10.147.18.185 Connecting to host 10.147.18.185, port 5201 [ 5] local 10.147.18.65 port 49460 connected to 10.147.18.185 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 1.23 MBytes 10.3 Mbits/sec 1 88.6 KBytes [ 5] 1.00-2.00 sec 1.15 MBytes 9.61 Mbits/sec 5 77.8 KBytes [ 5] 2.00-3.00 sec 1.08 MBytes 9.10 Mbits/sec 7 51.0 KBytes [ 5] 3.00-4.00 sec 1.08 MBytes 9.10 Mbits/sec 0 77.8 KBytes [ 5] 4.00-5.00 sec 1.08 MBytes 9.10 Mbits/sec 0 96.6 KBytes [ 5] 5.00-6.00 sec 1.08 MBytes 9.10 Mbits/sec 4 48.3 KBytes [ 5] 6.00-7.00 sec 1.08 MBytes 9.10 Mbits/sec 0 75.1 KBytes [ 5] 7.00-8.00 sec 1.08 MBytes 9.10 Mbits/sec 0 93.9 KBytes [ 5] 8.00-9.00 sec 1.08 MBytes 9.10 Mbits/sec 1 83.2 KBytes [ 5] 9.00-10.00 sec 1.08 MBytes 9.10 Mbits/sec 5 34.9 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 11.1 MBytes 9.27 Mbits/sec 23 sender [ 5] 0.00-10.03 sec 10.8 MBytes 9.03 Mbits/sec receiver iperf Done. root@len:/home/kevin# root@intel:~# iperf3 -c 10.147.18.185 Connecting to host 10.147.18.185, port 5201 [ 5] local 10.147.18.84 port 46324 connected to 10.147.18.185 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 1.45 MBytes 12.1 Mbits/sec 10 48.3 KBytes [ 5] 1.00-2.00 sec 926 KBytes 7.58 Mbits/sec 3 51.0 KBytes [ 5] 2.00-3.00 sec 1.08 MBytes 9.10 Mbits/sec 0 77.8 KBytes [ 5] 3.00-4.00 sec 1.08 MBytes 9.10 Mbits/sec 13 32.2 KBytes [ 5] 4.00-5.00 sec 926 KBytes 7.58 Mbits/sec 1 53.7 KBytes [ 5] 5.00-6.00 sec 1.27 MBytes 10.6 Mbits/sec 1 56.4 KBytes [ 5] 6.00-7.00 sec 1.15 MBytes 9.61 Mbits/sec 1 53.7 KBytes [ 5] 7.00-8.00 sec 1.08 MBytes 9.10 Mbits/sec 1 64.4 KBytes [ 5] 8.00-9.00 sec 1.08 MBytes 9.10 Mbits/sec 1 64.4 KBytes [ 5] 9.00-10.00 sec 1.08 MBytes 9.10 Mbits/sec 2 45.6 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 11.1 MBytes 9.30 Mbits/sec 33 sender [ 5] 0.00-10.03 sec 10.8 MBytes 9.03 Mbits/sec receiver iperf Done. root@intel:~# root@asus:/home/kevin# iperf3 -c 10.147.18.185 Connecting to host 10.147.18.185, port 5201 [ 5] local 10.147.18.14 port 43012 connected to 10.147.18.185 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 1.31 MBytes 10.9 Mbits/sec 1 93.9 KBytes [ 5] 1.00-2.00 sec 1.08 MBytes 9.10 Mbits/sec 0 113 KBytes [ 5] 2.00-3.00 sec 1.21 MBytes 10.1 Mbits/sec 2 93.9 KBytes [ 5] 3.00-4.00 sec 741 KBytes 6.07 Mbits/sec 11 26.8 KBytes [ 5] 4.00-5.00 sec 802 KBytes 6.57 Mbits/sec 1 51.0 KBytes [ 5] 5.00-6.00 sec 1.08 MBytes 9.10 Mbits/sec 0 75.1 KBytes [ 5] 6.00-7.00 sec 1.02 MBytes 8.60 Mbits/sec 1 72.5 KBytes [ 5] 7.00-8.00 sec 1.02 MBytes 8.59 Mbits/sec 1 64.4 KBytes [ 5] 8.00-9.00 sec 1.08 MBytes 9.11 Mbits/sec 0 85.9 KBytes [ 5] 9.00-10.00 sec 1.08 MBytes 9.10 Mbits/sec 1 77.8 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 10.4 MBytes 8.73 Mbits/sec 18 sender [ 5] 0.00-10.07 sec 10.2 MBytes 8.51 Mbits/sec receiver iperf Done. root@asus:/home/kevin#
I then closed down the zerotier VPN on len and did a test from len via the external internet to gemini, ie not using the VPN:
root@len:/home/kevin# systemctl stop zerotier-one
(obviously at that point the vpn connection lost as I was connected via an ssh session).
root@gemini:/home/kevin# iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 5.146.192.17, port 59644 [ 5] local 45.76.140.242 port 5201 connected to 5.146.192.17 port 59646 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 974 KBytes 7.97 Mbits/sec [ 5] 1.00-2.00 sec 1.14 MBytes 9.55 Mbits/sec [ 5] 2.00-3.00 sec 1.16 MBytes 9.73 Mbits/sec [ 5] 3.00-4.00 sec 1.15 MBytes 9.61 Mbits/sec [ 5] 4.00-5.00 sec 1.12 MBytes 9.43 Mbits/sec [ 5] 5.00-6.00 sec 1.16 MBytes 9.73 Mbits/sec [ 5] 6.00-7.00 sec 1.11 MBytes 9.27 Mbits/sec [ 5] 7.00-8.00 sec 1.16 MBytes 9.70 Mbits/sec [ 5] 8.00-9.00 sec 1.08 MBytes 9.07 Mbits/sec [ 5] 9.00-10.00 sec 1.14 MBytes 9.57 Mbits/sec [ 5] 10.00-10.03 sec 28.9 KBytes 9.35 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate [ 5] 0.00-10.03 sec 11.2 MBytes 9.36 Mbits/sec receiver ----------------------------------------------------------- Server listening on 5201 -----------------------------------------------------------
There was no difference in speed. No difference in speed either if len is disconnected from vpn, the other clients show same speeds.
root@gemini:/home/kevin# ufw allow 5201 Rule added Rule added (v6) root@gemini:/home/kevin# root@gemini:/home/kevin# iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 10.147.18.84, port 46580 [ 5] local 10.147.18.185 port 5201 connected to 10.147.18.84 port 46582 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 1.07 MBytes 8.97 Mbits/sec [ 5] 1.00-2.00 sec 1.00 MBytes 8.40 Mbits/sec [ 5] 2.00-3.00 sec 1.01 MBytes 8.46 Mbits/sec [ 5] 3.00-4.00 sec 1.13 MBytes 9.48 Mbits/sec [ 5] 4.00-5.00 sec 1.14 MBytes 9.56 Mbits/sec [ 5] 5.00-6.00 sec 1.07 MBytes 8.99 Mbits/sec [ 5] 6.00-7.00 sec 993 KBytes 8.13 Mbits/sec [ 5] 7.00-8.00 sec 1.13 MBytes 9.45 Mbits/sec [ 5] 8.00-9.00 sec 1.13 MBytes 9.52 Mbits/sec [ 5] 9.00-10.00 sec 1.12 MBytes 9.43 Mbits/sec [ 5] 10.00-10.05 sec 53.7 KBytes 9.37 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate [ 5] 0.00-10.05 sec 10.8 MBytes 9.04 Mbits/sec receiver ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- ^X^Z [1]+ Stopped iperf3 -s root@gemini:/home/kevin# ufw enable Command may disrupt existing ssh connections. Proceed with operation (y|n)? y Firewall is active and enabled on system startup root@gemini:/home/kevin# root@intel:~# iperf3 -c 10.147.18.185 Connecting to host 10.147.18.185, port 5201 [ 5] local 10.147.18.84 port 46582 connected to 10.147.18.185 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 1.46 MBytes 12.3 Mbits/sec 1 85.9 KBytes [ 5] 1.00-2.00 sec 926 KBytes 7.58 Mbits/sec 11 26.8 KBytes [ 5] 2.00-3.00 sec 1.08 MBytes 9.10 Mbits/sec 0 59.0 KBytes [ 5] 3.00-4.00 sec 1.08 MBytes 9.10 Mbits/sec 1 59.0 KBytes [ 5] 4.00-5.00 sec 1.08 MBytes 9.10 Mbits/sec 0 83.2 KBytes [ 5] 5.00-6.00 sec 1.08 MBytes 9.10 Mbits/sec 11 32.2 KBytes [ 5] 6.00-7.00 sec 1.08 MBytes 9.10 Mbits/sec 1 56.4 KBytes [ 5] 7.00-8.00 sec 1.08 MBytes 9.10 Mbits/sec 0 80.5 KBytes [ 5] 8.00-9.00 sec 1.15 MBytes 9.61 Mbits/sec 1 75.1 KBytes [ 5] 9.00-10.00 sec 1.08 MBytes 9.10 Mbits/sec 5 53.7 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 11.1 MBytes 9.32 Mbits/sec 31 sender [ 5] 0.00-10.05 sec 10.8 MBytes 9.04 Mbits/sec receiver iperf Done. root@intel:~# root@gemini:/home/kevin# ufw deny 5201 Rule updated Rule updated (v6) root@gemini:/home/kevin#
I then also did a speed test using two laptops, rather than the server. speed test with iperf3 from asus to intel is much faster:
root@asus:/home/kevin/LOCAL# iperf3 -c intelvpn Connecting to host intelvpn, port 5201 [ 5] local 10.147.18.14 port 50668 connected to 10.147.18.84 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 4.00 MBytes 33.6 Mbits/sec 1 252 KBytes [ 5] 1.00-2.00 sec 4.82 MBytes 40.5 Mbits/sec 2 271 KBytes [ 5] 2.00-3.00 sec 4.64 MBytes 38.9 Mbits/sec 0 295 KBytes [ 5] 3.00-4.00 sec 5.49 MBytes 46.0 Mbits/sec 1 317 KBytes [ 5] 4.00-5.00 sec 5.85 MBytes 49.0 Mbits/sec 0 344 KBytes [ 5] 5.00-6.00 sec 6.21 MBytes 52.1 Mbits/sec 9 263 KBytes [ 5] 6.00-7.00 sec 4.28 MBytes 35.9 Mbits/sec 1 293 KBytes [ 5] 7.00-8.00 sec 5.42 MBytes 45.5 Mbits/sec 1 317 KBytes [ 5] 8.00-9.00 sec 7.11 MBytes 59.7 Mbits/sec 3 338 KBytes [ 5] 9.00-10.00 sec 6.81 MBytes 57.1 Mbits/sec 9 255 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 54.6 MBytes 45.8 Mbits/sec 27 sender [ 5] 0.00-10.04 sec 53.8 MBytes 44.9 Mbits/sec receiver iperf Done. root@asus:/home/kevin/LOCAL# root@intel:/home/kevin# ufw allow 5201 Rule added Rule added (v6) root@intel:/home/kevin# iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 10.147.18.14, port 50666 [ 5] local 10.147.18.84 port 5201 connected to 10.147.18.14 port 50668 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 3.60 MBytes 30.2 Mbits/sec [ 5] 1.00-2.00 sec 4.62 MBytes 38.7 Mbits/sec [ 5] 2.00-3.00 sec 4.53 MBytes 38.0 Mbits/sec [ 5] 3.00-4.00 sec 5.47 MBytes 45.9 Mbits/sec [ 5] 4.00-5.00 sec 6.03 MBytes 50.6 Mbits/sec [ 5] 5.00-6.00 sec 5.80 MBytes 48.7 Mbits/sec [ 5] 6.00-7.00 sec 4.20 MBytes 35.3 Mbits/sec [ 5] 7.00-8.00 sec 5.86 MBytes 49.2 Mbits/sec [ 5] 8.00-9.00 sec 6.74 MBytes 56.5 Mbits/sec [ 5] 9.00-10.00 sec 6.71 MBytes 56.3 Mbits/sec [ 5] 10.00-10.04 sec 215 KBytes 48.3 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate [ 5] 0.00-10.04 sec 53.8 MBytes 44.9 Mbits/sec receiver ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- a bit slower with the len to intel:
root@len:/home/kevin# iperf3 -c intelvpn Connecting to host intelvpn, port 5201 [ 5] local 10.147.18.65 port 55332 connected to 10.147.18.84 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 4.24 MBytes 35.6 Mbits/sec 1 204 KBytes [ 5] 1.00-2.00 sec 3.98 MBytes 33.4 Mbits/sec 2 225 KBytes [ 5] 2.00-3.00 sec 3.92 MBytes 32.9 Mbits/sec 1 247 KBytes [ 5] 3.00-4.00 sec 4.10 MBytes 34.4 Mbits/sec 7 188 KBytes [ 5] 4.00-5.00 sec 4.22 MBytes 35.4 Mbits/sec 0 233 KBytes [ 5] 5.00-6.00 sec 4.16 MBytes 34.9 Mbits/sec 0 258 KBytes [ 5] 6.00-7.00 sec 4.04 MBytes 33.9 Mbits/sec 0 268 KBytes [ 5] 7.00-8.00 sec 3.68 MBytes 30.8 Mbits/sec 0 282 KBytes [ 5] 8.00-9.00 sec 3.92 MBytes 32.9 Mbits/sec 0 301 KBytes [ 5] 9.00-10.00 sec 3.74 MBytes 31.3 Mbits/sec 0 319 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 40.0 MBytes 33.5 Mbits/sec 11 sender [ 5] 0.00-10.08 sec 39.7 MBytes 33.0 Mbits/sec receiver iperf Done. root@len:/home/kevin# # from len to asus:
root@len:/home/kevin# iperf3 -c asusvpn Connecting to host asusvpn, port 5201 [ 5] local 10.147.18.65 port 59526 connected to 10.147.18.14 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 3.41 MBytes 28.6 Mbits/sec 1 169 KBytes [ 5] 1.00-2.00 sec 1.81 MBytes 15.2 Mbits/sec 18 102 KBytes [ 5] 2.00-3.00 sec 3.92 MBytes 32.9 Mbits/sec 1 145 KBytes [ 5] 3.00-4.00 sec 4.64 MBytes 38.9 Mbits/sec 0 185 KBytes [ 5] 4.00-5.00 sec 2.35 MBytes 19.7 Mbits/sec 8 102 KBytes [ 5] 5.00-6.00 sec 1.63 MBytes 13.7 Mbits/sec 0 129 KBytes [ 5] 6.00-7.00 sec 3.44 MBytes 28.8 Mbits/sec 1 156 KBytes [ 5] 7.00-8.00 sec 4.10 MBytes 34.4 Mbits/sec 4 150 KBytes [ 5] 8.00-9.00 sec 2.53 MBytes 21.2 Mbits/sec 6 126 KBytes [ 5] 9.00-10.00 sec 1.57 MBytes 13.1 Mbits/sec 2 145 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 29.4 MBytes 24.6 Mbits/sec 41 sender [ 5] 0.00-10.01 sec 29.1 MBytes 24.4 Mbits/sec receiver iperf Done. root@len:/home/kevin# root@asus:/# iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 10.147.18.65, port 59524 [ 5] local 10.147.18.14 port 5201 connected to 10.147.18.65 port 59526 [ ID] Interval Transfer Bitrate [ 5] 0.00-1.00 sec 3.01 MBytes 25.2 Mbits/sec [ 5] 1.00-2.00 sec 1.71 MBytes 14.4 Mbits/sec [ 5] 2.00-3.00 sec 3.99 MBytes 33.5 Mbits/sec [ 5] 3.00-4.00 sec 4.57 MBytes 38.4 Mbits/sec [ 5] 4.00-5.00 sec 2.43 MBytes 20.4 Mbits/sec [ 5] 5.00-6.00 sec 1.64 MBytes 13.7 Mbits/sec [ 5] 6.00-7.00 sec 3.41 MBytes 28.6 Mbits/sec [ 5] 7.00-8.00 sec 4.10 MBytes 34.4 Mbits/sec [ 5] 8.00-9.00 sec 2.60 MBytes 21.8 Mbits/sec [ 5] 9.00-10.00 sec 1.67 MBytes 14.0 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate [ 5] 0.00-10.01 sec 29.1 MBytes 24.4 Mbits/sec receiver ----------------------------------------------------------- Server listening on 5201 -----------------------------------------------------------
root@len:~# iperf3 iperf3: parameter error - must either be a client (-c) or server (-s) Usage: iperf3 [-s|-c host] [options] iperf3 [-h|--help] [-v|--version] Server or Client: -p, --port # server port to listen on/connect to -f, --format [kmgtKMGT] format to report: Kbits, Mbits, Gbits, Tbits -i, --interval # seconds between periodic throughput reports -F, --file name xmit/recv the specified file -A, --affinity n/n,m set CPU affinity -B, --bind <host> bind to the interface associated with the address <host> -V, --verbose more detailed output -J, --json output in JSON format --logfile f send output to a log file --forceflush force flushing output at every interval -d, --debug emit debugging output -v, --version show version information and quit -h, --help show this message and quit Server specific: -s, --server run in server mode -D, --daemon run the server as a daemon -I, --pidfile file write PID file -1, --one-off handle one client connection then exit --rsa-private-key-path path to the RSA private key used to decrypt authentication credentials --authorized-users-path path to the configuration file containing user credentials Client specific: -c, --client <host> run in client mode, connecting to <host> --sctp use SCTP rather than TCP -X, --xbind <name> bind SCTP association to links --nstreams # number of SCTP streams -u, --udp use UDP rather than TCP --connect-timeout # timeout for control connection setup (ms) -b, --bitrate #[KMG][/#] target bitrate in bits/sec (0 for unlimited) (default 1 Mbit/sec for UDP, unlimited for TCP) (optional slash and packet count for burst mode) --pacing-timer #[KMG] set the timing for pacing, in microseconds (default 1000) --fq-rate #[KMG] enable fair-queuing based socket pacing in bits/sec (Linux only) -t, --time # time in seconds to transmit for (default 10 secs) -n, --bytes #[KMG] number of bytes to transmit (instead of -t) -k, --blockcount #[KMG] number of blocks (packets) to transmit (instead of -t or -n) -l, --length #[KMG] length of buffer to read or write (default 128 KB for TCP, dynamic or 1460 for UDP) --cport <port> bind to a specific client port (TCP and UDP, default: ephemeral port) -P, --parallel # number of parallel client streams to run -R, --reverse run in reverse mode (server sends, client receives) --bidir run in bidirectional mode. Client and server send and receive data. -w, --window #[KMG] set window size / socket buffer size -C, --congestion <algo> set TCP congestion control algorithm (Linux and FreeBSD only) -M, --set-mss # set TCP/SCTP maximum segment size (MTU - 40 bytes) -N, --no-delay set TCP/SCTP no delay, disabling Nagle's Algorithm -4, --version4 only use IPv4 -6, --version6 only use IPv6 -S, --tos N set the IP type of service, 0-255. The usual prefixes for octal and hex can be used, i.e. 52, 064 and 0x34 all specify the same value. --dscp N or --dscp val set the IP dscp value, either 0-63 or symbolic. Numeric values can be specified in decimal, octal and hex (see --tos above). -L, --flowlabel N set the IPv6 flow label (only supported on Linux) -Z, --zerocopy use a 'zero copy' method of sending data -O, --omit N omit the first n seconds -T, --title str prefix every output line with this string --extra-data str data string to include in client and server JSON --get-server-output get results from server --udp-counters-64bit use 64-bit counters in UDP test packets --repeating-payload use repeating pattern in payload, instead of randomized payload (like in iperf2) --username username for authentication --rsa-public-key-path path to the RSA public key used to encrypt authentication credentials [KMG] indicates options that support a K/M/G suffix for kilo-, mega-, or giga- iperf3 homepage at: https://software.es.net/iperf/ Report bugs to: https://github.com/esnet/iperf root@len:~#