Packet drops with USB (Gigabit) Ethernet adapter with ASIX chipset

Hi,

I've bought a USB 3.0 10/100/1000 Ethernet adapter with AX88179 chipset from UGREEN to capture packets with Wireshark 3.2.3/3.2.4 on my Win10 client.

When I did the first capture I realized that there are a lot of "Previous segment not captured" messages in different TCP streams. So I started a second capture on the client side interface to compare them both. The capture of the client sides interface had no lost packets, but the capture of the USB adapter showed about 200 "Previous segment not captured" messages in one minute of 200 kbit/s traffic.

To verify that the adapter has no hardware defect, I tried some other adapters:

• UGREEN USB 3.0 Gigabit 10/100/1000Mbps Ethernet Adapter (ASIX AX88179)

• Plugable USB 3.0 Gigabit Ethernet Adapter USB3-E1000 (ASIX AX88179)

• Plugable USB 2.0 Ethernet Adapter USB2-E100 (ASIX AX88772)

All of them are having the same issue.
I've already did the following troubleshootings without success:

• Changed original drivers of USB adapters to the one from ASIX

• Tested adapters with another Win10 client

• Capture with an internal on-board-LAN port from Realtek with the same span port -> no "Previous segment not captured" messages. Conclusion: Switch/span port is fine.

• Gigabit USB adapters has no packet drops as LAN interface. 952 Mbit/s throughput (iPerf3) without unusual error frames.

• Disabled all energy-saving and offloading options of the USB adapters

• Raised capture buffer to 500MB

• Captured with dumpcap.exe (the summary at the end says "No lost packets")

• Downgrade npcap from 0.9991 to 0.9987

Now I'm not sure if this is an issue with ASIX chipset in general, or something with npcap. I'm also wondering why I haven't found any other reports related to this behaviour. Is it me only?

DiagReport-20200522-161455.txt

Start with the attached DiagReport-20200522-161455.txt and reproduce the comparison on Windows 10 using the listed ASIX adapters, Wireshark, and dumpcap.exe. Compare USB-adapter captures with the onboard Realtek capture and determine whether packet loss originates in npcap or the ASIX path; done means the cause is isolated and the reported drops are resolved or clearly documented.