This can help to solve the problem...
Pay attention:
RPi3B+ internal gigabit NIC...
pi@raspberrypi:~ $ sudo iperf3 -c XXX.XXX.X.XXX ...
sending from pi to my big PC
Connecting to host
big PC, port 5201
[ 4] local
RPi3B+ port 54914 connected to
big PC port 5201
[ ID] Interval Transfer Bandwidth
Retr Cwnd
[ 4] 0.00-1.00 sec 37.9 MBytes 318 Mbits/sec
0 257 KBytes
[ 4] 1.00-2.00 sec 37.7 MBytes 316 Mbits/sec
0 270 KBytes
[ 4] 2.00-3.00 sec 37.8 MBytes 317 Mbits/sec
0 284 KBytes
[ 4] 3.00-4.00 sec 37.7 MBytes 316 Mbits/sec
0 298 KBytes
[ 4] 4.00-5.00 sec 37.5 MBytes 314 Mbits/sec
0 317 KBytes
[ 4] 5.00-6.00 sec 37.7 MBytes 316 Mbits/sec
0 317 KBytes
[ 4] 6.00-7.00 sec 37.7 MBytes 316 Mbits/sec
0 331 KBytes
[ 4] 7.00-8.00 sec 37.7 MBytes 316 Mbits/sec
0 349 KBytes
[ 4] 8.00-9.00 sec 37.6 MBytes 315 Mbits/sec
0 387 KBytes
[ 4] 9.00-10.00 sec 37.7 MBytes 316 Mbits/sec
0 387 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
Retr
[ 4] 0.00-10.00 sec 377 MBytes 316 Mbits/sec
0 sender
[ 4] 0.00-10.00 sec 376 MBytes
315 Mbits/sec receiver
iperf Done.
pi@raspberrypi:~ $ sudo iperf3 -c XXX.XXX.X.XXX -R
Connecting to host
big PC, port 5201
Reverse mode, remote host
big PC is sending
[ 4] local
RPi3B+ port 54918 connected to
big PC port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 27.2 MBytes 228 Mbits/sec
[ 4] 1.00-2.00 sec 27.1 MBytes 227 Mbits/sec
[ 4] 2.00-3.00 sec 27.0 MBytes 227 Mbits/sec
[ 4] 3.00-4.00 sec 27.3 MBytes 229 Mbits/sec
[ 4] 4.00-5.00 sec 25.6 MBytes 214 Mbits/sec
[ 4] 5.00-6.00 sec 25.0 MBytes 209 Mbits/sec
[ 4] 6.00-7.00 sec 26.1 MBytes 219 Mbits/sec
[ 4] 7.00-8.00 sec 25.9 MBytes 217 Mbits/sec
[ 4] 8.00-9.00 sec 25.0 MBytes 210 Mbits/sec
[ 4] 9.00-10.00 sec 26.2 MBytes 220 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
Retr
[ 4] 0.00-10.00 sec 262 MBytes 220 Mbits/sec
3281 sender
[ 4] 0.00-10.00 sec 262 MBytes
220 Mbits/sec receiver
iperf Done.
Now:
RPi3B+
USB 3.0 hub with gigabit NIC lsmod reports
ax88179_178a kernel module...
RPi3B+ internal gigabit NIC is now down.
pi@raspberrypi:~ $ sudo iperf3 -c XXX.XXX.X.XXX ...
sending from pi to my big PC
Connecting to host
big PC, port 5201
[ 4] local
RPi3B+ port 54016 connected to
big PC port 5201
[ ID] Interval Transfer Bandwidth
Retr Cwnd
[ 4] 0.00-1.00 sec 21.7 MBytes 182 Mbits/sec
0 38.2 KBytes
[ 4] 1.00-2.00 sec 21.8 MBytes 183 Mbits/sec
0 42.4 KBytes
[ 4] 2.00-3.00 sec 21.8 MBytes 183 Mbits/sec
0 45.2 KBytes
[ 4] 3.00-4.00 sec 21.6 MBytes 181 Mbits/sec
0 69.3 KBytes
[ 4] 4.00-5.00 sec 21.6 MBytes 181 Mbits/sec
0 69.3 KBytes
[ 4] 5.00-6.00 sec 21.7 MBytes 182 Mbits/sec
0 103 KBytes
[ 4] 6.00-7.00 sec 21.8 MBytes 183 Mbits/sec
0 156 KBytes
[ 4] 7.00-8.00 sec 22.0 MBytes 184 Mbits/sec
0 156 KBytes
[ 4] 8.00-9.00 sec 22.1 MBytes 185 Mbits/sec
0 233 KBytes
[ 4] 9.00-10.00 sec 21.9 MBytes 184 Mbits/sec
0 233 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
Retr
[ 4] 0.00-10.00 sec 218 MBytes 183 Mbits/sec
0 sender
[ 4] 0.00-10.00 sec 217 MBytes
182 Mbits/sec receiver
iperf Done.
pi@raspberrypi:~ $ sudo iperf3 -c XXX.XXX.X.XXX -R
Connecting to host
big PC, port 5201
Reverse mode, remote host
big PC is sending
[ 4] local
RPi3B+ port 54020 connected to
big PC port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 20.3 MBytes 170 Mbits/sec
[ 4] 1.00-2.00 sec 20.6 MBytes 173 Mbits/sec
[ 4] 2.00-3.00 sec 20.8 MBytes 174 Mbits/sec
[ 4] 3.00-4.00 sec 20.6 MBytes 173 Mbits/sec
[ 4] 4.00-5.00 sec 20.5 MBytes 172 Mbits/sec
[ 4] 5.00-6.00 sec 20.3 MBytes 170 Mbits/sec
[ 4] 6.00-7.00 sec 20.6 MBytes 173 Mbits/sec
[ 4] 7.00-8.00 sec 21.0 MBytes 176 Mbits/sec
[ 4] 8.00-9.00 sec 19.3 MBytes 162 Mbits/sec
[ 4] 9.00-10.00 sec 20.7 MBytes 174 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
Retr
[ 4] 0.00-10.00 sec 205 MBytes 172 Mbits/sec
3368 sender
[ 4] 0.00-10.00 sec 205 MBytes
172 Mbits/sec receiver
iperf Done.
---
We can see that
ethernet gigabit usb adapter (
ax88179_178a kernel module) performs a little less than internal gigabit adapter RPi3B+.
But both internal and external gigabits NIC on RPi3B+ have RX loss packets to show us
Retr column.
Then,
lan78xx kernel driver is not the problem.The same problem exists with
ax88179_178a lan kernel module.
Same problem on old RPi3B not plus latest raspbian OS.
Then... the problem is on Raspbian kernel.
---
Same net, same cable, same router port, and iperf3 test from tinkerboard to big PC and back.
0 Retr sending and receiving.Then no hardware problem on my net in all test in this thread.Problem appears using RPi.

- iperf3-on-tinkerboard-on-same-net-cable-router-port-that-rpi3b-plus-before-tested.png (228.8 KiB) Viewed 8042 times