Working stable, DS1515+ (avaton) with RTL8156B (Disable jumbo frames)

[manors]

Description of the problem

The initial setting of iperf3 can only run for 200 seconds before it stops working.

I tried the following:

1. Change the USB port that is inserted. There are 4 USB3.0 ports on the back of DS1515+, but not on the front. Only ports 2 and 3 can run for about 200 seconds, and the other ports will crash faster. The speed of iperf3 on port 1 is only 1.3Gbps.

---

|1___2|
|3___4|
|__________|
2. Use a dual-powered USB interface, but it doesn't work. It even crashes faster.
3. Remove the USB network card shell and stick a heat sink on the chip. It has a little effect, which extends the crash time by about ten seconds.
4. I removed the dual-powered USB extension cable because it was useless. Then replace it with a better network cable, still CAT5E cable. The speed of iperf3 has increased, from less than 1.8Gbps at the beginning to 2.37Gbps, but it still crashes.
5. After turning off jumbo frames on the middle switch, ports 1 and 4 still crash for a short time. But if connected to USB ports 2 and 3 will run stably. iperf3 reports a stable speed of 2.37Gbps. It has been running stably for an hour.

Summary:
I am not sure which specific steps solved this problem. I hope it will be helpful to you.

Description of your products

DS1515+
Linux 3.10.105 #25556 SMP Tue Mar 21 22:24:38 CST 2023 x86_64 GNU/Linux synology_avoton_1515+
DSM version 6.2.4-25556 Update 7
Seekswan USB-A RTL8156B 2.5G
Driver: 2.18.1-1

Description of your environment

• using a Ethernet switch
  • PC: NIC model I226
  • Ethernet switch: Seekswan 42.5G 210G switch
• cable category Cat.5e

Output of lsusb command

|__usb1          1d6b:0002:0310 09  2.00  480MBit/s 0mA 1IF  (ehci_hcd 0000:00:16.0) hub
  |__1-1         8087:07db:0002 09  2.00  480MBit/s 0mA 1IF  ( ffffffd1ffffffb2ffffffdbffffffad) hub
    |__1-1.1     f400:f400:0100 00  2.00  480MBit/s 200mA 1IF  (Synology DiskStation 65005BD063A34F96)
|__usb2          1d6b:0002:0310 09  2.00  480MBit/s 0mA 1IF  (Linux 3.10.105 etxhci_hcd-170202 Etron xHCI Host Controller 0000:04:00.0) hub
|__usb3          1d6b:0003:0310 09  3.00 5000MBit/s 0mA 1IF  (Linux 3.10.105 etxhci_hcd-170202 Etron xHCI Host Controller 0000:04:00.0) hub
  |__3-1         0bda:8156:3104 00  3.20 5000MBit/s 256mA 1IF  (Realtek USB 10/100/1G/2.5G LAN 401000001)````

### Output of ``ifconfig -a`` command

(paste output here)

[manors]

Update:
use iperf3 --bidir do test still unstable, after 200 seconds it stops working.
without --bidir can stable working.