Asus RT-AC66U B1 poor USB performance tethering


New Around Here

I've been using RT-AC66U B1 with Samsung S9 and S10e using USB tethering. I've had 200Mbps connection through 4G earlier and I've got around 170Mbps on speedtest through LAN. So, I've been happy with that.

Now, I have updated my connection to 400Mbps and I'm still getting around 170Mbps on speedtest. If I connect the phone with same cable to my PC directly, I'm getting almost 400Mbps on connection tests. Both the USB2.0 and USB3.0 ports on the router give the same 170Mbps speed.

I tried USB performance with HDD on the router and got like 25MB/s on USB2.0 and 35MB/s on USB3.0 ports("10 times the speed" yeah right....) . Same HDD on PC USB2.0 port gives like 120MB/s.

With tethering, router's CPU usage goes to Core 1 40%, Core 2 90%. It seems like it's just capping the speed to 170Mbps. There is no fluctuation.

Is this router just crap or can I get better performance with Merlin or something?


Part of the Furniture
Routers are notoriously poor performers when it comes to USB. They simply were never designed to compete w/ the desktop in this regard. That's why I strongly discourage users from trying to treat them as a true NAS. They're NOT. NOT by any stretch. So I wouldn't expect USB tethering to perform all that much better.

IOW, while I can't give you exact numbers to expect, as you describe it, I'm NOT surprised. Sounds just about right to me based on my own USB experiences w/ various routers over the years.
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Part of the Furniture
USB performance with a drive does not equal the same throughput when tethering. I suspect the router is doing what it can do. You might explore other options.


Part of the Furniture
That model of router is only capable of ~200Mbps throughput WAN to LAN when using Ethernet unless hardware acceleration is being used. At higher speeds it becomes CPU limited (on a single core) without hardware acceleration enabled. As you are using USB tethering I doubt that hardware acceleration is applicable. So in summary, your results are not unexpected for that model.


New Around Here
I "fixed" it by buying Huawei outside 4G/5G modem and plugged that in to the WAN port. Now I'm getting 400/100Mbps Internet. I didn't even know that I could upload 100Mbps with this connection...

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