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Feb 18, 2019

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.

Feb 18, 2019


Thanks much for the feedback.

Regarding RTL8153, I have 3 different vendors' adaptors and all of them working fine on my side. Let's see if any other folks have such issue also for the feedback.

I agree with you that adding if_ure should support them better, meanwhile, cdce is simple and no much needs to configure the hardware or the hardware do not comply the cdce spec well. We will add that in the following update as additional benefit is we can support more devices.

While, at currently stage, one thing I can imagine to have a try but can not guarantee is, Would you mind plug the devices on a Win* host first on a USB3 port and then plug it back on the platform back to see if it works for you or not? If it's not, I am afraid we may need wait a while for next release. Sorry for the convenience as we have never see such issue before.

Regarding ASIX, we are working on that now.

Feb 15, 2022

Hello Songtao

I have a similar issue with Realtek USB 101001G2.5G LAN 0bda:8156 and a TP Link TL-SG108-M2 8 port unmanaged switch.

After ESXi reboot the nic connects with 100mbps speed and not 2.5G. If I disconnect/reconnect the lan cable (CAT6 15 cm) I get 2.5G speed. But not every time I reboot. Sometime both nic gets 100mbps and other time only vusb0 get 100mbps and vusb1 gets 2.5G.

NUC7i3BNK, VMware ESXi, 7.0.3, 18644231 with installed and modified to with for link.


Feb 25, 2019

Hi Songtao,

I have been able to trace the issue with the Realtek driver when using the Ubquiti US-16 switch to being a problem with the switch itself. The advertised speed was just being discarded… I have now been able to validate the both adapters work.With the Cisco router, it seems I just got the cabling wrong when moving from one switch to another.

However, attempts to run iperf against the ASIX adapter, as a server, will result on the following messages on vmkernel.log:

2019-02-16T09:29:11.043Z cpu2:2097548)usbd_setup_ctrl_transfer:1538: Wrong framelength 0 != 8

This seems to be related to the TCP window size used — anything other than 64k will crash the adapter and generate those messages until a reboot.

Overall, the performance is adequate, but I am still getting better results when using my own Linux based drivers.

Looking forward to the next iteration of the fling, though.


Feb 19, 2019

Hi Songtao,

Thank you for you response, but unfortunately I don't have anything other than VMs running Windows.

Anyway, I know the adapters I have tested advertise and link at 1000 Mbps, plugged on the same USB ports and to the same switch ports. I use my own porting of the Realtek Linux driver and it works just fine on ESXi.

I will just wait for the next version of the fling and test again. Although I can simply carry on using my own drivers, it would be a nice option to have once the Linux subsystem is completely removed from ESXi.

By the way, thanks for the great work and the prompt response.