Hello,
can anyone advise why are there so many Retries when I try to do iperf3 BW test from PC-A to PC-B? The network map looks like this:
PC-A ----- ether4 on RB951G-2HnD - ether5 on same MT ----- PC-B
Here is the iperf3 output:
user@ubuntu-1:~$ iperf3 -c 192.168.20.254 -i 5 -t 60
Connecting to host 192.168.20.254, port 5201
[ 4] local 192.168.10.253 port 39188 connected to 192.168.20.254 port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-5.00 sec 542 MBytes 910 Mbits/sec 458 72.1 KBytes
[ 4] 5.00-10.00 sec 548 MBytes 919 Mbits/sec 753 219 KBytes
[ 4] 10.00-15.00 sec 547 MBytes 917 Mbits/sec 636 194 KBytes
[ 4] 15.00-20.00 sec 547 MBytes 918 Mbits/sec 676 201 KBytes
[ 4] 20.00-25.00 sec 545 MBytes 914 Mbits/sec 667 247 KBytes
[ 4] 25.00-30.00 sec 547 MBytes 918 Mbits/sec 781 73.5 KBytes
[ 4] 30.00-35.00 sec 545 MBytes 914 Mbits/sec 729 70.7 KBytes
[ 4] 35.00-40.00 sec 546 MBytes 916 Mbits/sec 666 320 KBytes
[ 4] 40.00-45.00 sec 545 MBytes 914 Mbits/sec 912 73.5 KBytes
[ 4] 45.00-50.00 sec 547 MBytes 918 Mbits/sec 742 281 KBytes
[ 4] 50.00-55.00 sec 548 MBytes 919 Mbits/sec 663 69.3 KBytes
[ 4] 55.00-60.00 sec 547 MBytes 917 Mbits/sec 875 173 KBytes
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-60.00 sec 6.40 GBytes 916 Mbits/sec 8558 sender
[ 4] 0.00-60.00 sec 6.40 GBytes 916 Mbits/sec receiver
iperf Done.
user@ubuntu-1:~$
PC-A and PC-B are identical: Ubuntu 18.04 LTS virtualised on HP DL380 G7, assigned 8 cores of CPU, 8 GB RAM, 2 NICs (one for management, one for connection to MikroTik) 2nd NIC is vmnic2 or vmnic3.
PC-A: 192.168.10.253 and PC-B is 192.168.20.254
There is nothing configured on MikroTik (just basic configuration. IP addresses), no NAT,no queues, no FW rules, nothing.
CPU usage during one-way test (A to B or vice versa) is between 60 to 70%.
EDIT: SCENARIO 2
in scenario 2 I replaced RB951G-2HnD and used hAP ac, situation is very similar, still very high number of Retries:
user@ubuntu-1:~$ iperf3 -c 192.168.20.254 -i 5 -t 60
Connecting to host 192.168.20.254, port 5201
[ 4] local 192.168.10.253 port 39192 connected to 192.168.20.254 port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-5.00 sec 540 MBytes 905 Mbits/sec 1046 69.3 KBytes
[ 4] 5.00-10.00 sec 539 MBytes 904 Mbits/sec 1070 56.6 KBytes
[ 4] 10.00-15.00 sec 539 MBytes 904 Mbits/sec 1030 147 KBytes
[ 4] 15.00-20.00 sec 540 MBytes 906 Mbits/sec 1049 140 KBytes
[ 4] 20.00-25.00 sec 536 MBytes 898 Mbits/sec 1104 49.5 KBytes
[ 4] 25.00-30.00 sec 536 MBytes 900 Mbits/sec 1083 52.3 KBytes
[ 4] 30.00-35.00 sec 536 MBytes 900 Mbits/sec 1063 279 KBytes
[ 4] 35.00-40.00 sec 536 MBytes 900 Mbits/sec 1048 66.5 KBytes
[ 4] 40.00-45.00 sec 540 MBytes 907 Mbits/sec 1043 290 KBytes
[ 4] 45.00-50.00 sec 536 MBytes 900 Mbits/sec 1064 296 KBytes
[ 4] 50.00-55.00 sec 536 MBytes 900 Mbits/sec 1044 296 KBytes
[ 4] 55.00-60.00 sec 537 MBytes 901 Mbits/sec 1107 50.9 KBytes
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-60.00 sec 6.30 GBytes 902 Mbits/sec 12751 sender
[ 4] 0.00-60.00 sec 6.30 GBytes 902 Mbits/sec receiver
iperf Done.
user@ubuntu-1:~$
What could cause these problems? Posssibly faulty cables? MikroTik over-utilized? Something else?
Any idea is welcome.
Thank you.
