Hi Songtao, I had some time now to test the throughput of the ASIX and Realtek adapters. Whilst the performance of the ASIX adapter is generally good (TX is still lower than RX), with the Realtek adapters the performance is abysmal. Depending on the load, particularly when receiving packets, the Realtek adapter will seize up completely and more often than not have to be unplugged and replugged. Then, I realised that the link speed was coming up at 100 Mbps only. I have now tried with multiple Realtek based adapters (Anker, CableCreation and Rankie), and also on multiple switches (Ubiquiti US-16, Cisco SG300 and Cisco SG200); the result is always the same: 100 Mbps. Trying to set the switch port speed to manual kills the link immediately… Now, the ASIX disparity between TX and RX was already present on the Linux based driver William and yourself worked on. To resolve that, both tx-checksumming and scatter-gather must be set to "on" (that's what I did on my own driver). The issue with the Realtek driver is hard to say, but perhaps it is because you are only relying on the if_cdce and the usb-ethernet drivers. I suspect that using the r8153/r8152 specific FreeBSD driver (if_ure) would yield better results. The if_ure driver, like the if_axge driver you are using for the ASIX adapters, implements specific firmware functions of the adapter. Note 1: I have seen your reply on one of the existing comments saying that your own tests puts the performance of both ASIX and Realtek adapters on a par. Nobody else is mentioning anything about link speed… Am I the only one seeing the issue? Note 2: The ports on my test rig are definitely USB3 and I have confirmed multiple times that Gigabit speeds are achieved when using my Linux based drivers.