Ethernet Speed Capped by macOS over Thunderbolt?

Your title says it was capped over Thunderbolt. It looks like the speed was capped by USB hub. When connected to USB4 on your Mac, you get fast speeds. When connected to any of the Hubs, you seem to get USB3 capability. On newer Apple Silicon Macs, the USB side of things is USB4. So, if it is a USB to Ethernet, then it will be capped by the bus speed. The bus on the hub may only be USB3.

Also note that when using USB, all devices on the same bus share the total speed. When using Thunderbolt, all devices can exploit the top speed, if able. But, that adaptor would have to be Thunderbolt capable to use Thunderbolt.

Another USB shortfall (or maybe it is really a hub shortfall) is the bus may revert to a slower USB spec if there are slower devices connected to it. For instance, if you connect a USB2 device to a USB3 hub, the whole hub may function at USB2 speeds.

Corrode wrote:

The LG 5K Ultrafine connects to the Mac via a single Thunderbolt 3 connection. How is it not a Thunderbolt hub?

A Thunderbolt hub would have to have downstream Thunderbolt ports. Otherwise, it’s something else.

There is a lot of confusing marketing about Thunderbolt. 3rd party hardware manufacturers often use the word “Thunderbolt” when they mean USB-C.

Yes, there’s no apple hardware because they don’t make a USB-C to Ethernet adapter. They only sell the Belkin one via the Apple Store.

Thunderbolt to Gigabit Ethernet Adapter - Apple (CA)

Regarding the USB output of built-in hubs, where can I find those ratings?

I just googled the displays mentioned in the original, closed threads and in this one. If you click on the “specs” links on each, it describes what they support.

There is nothing that explicitly says they do or don’t support any specific devices. They just talk about protocols and speeds. Since neither has any downstream Thunderbolt ports, they can’t really be considered Thunderbolt hubs. They are USB hubs. It would be a question for those manufacturers whether or not they support gigabit Ethernet via your Belkin adapter. I doubt you would ever get an answer from them. Most hardware support people have no idea what Ethernet is. I’m quite sure that they haven’t tested this kind of configuration at all. Ethernet is uncommon and PCs tend to have Ethernet built-in, so they wouldn’t be trying to route it through the monitor.

It probably all boils down to how and where that transition from Thunderbolt to USB is taking place. That old thread described the configuration working correctly with a PC, but erroneously called it Thunderbolt. I can guarantee that no PC has Thunderbolt. That would be a pure USB connection. But with a Mac, it is likely talking Thunderbolt to the display and it is the display doing the downstream transition to USB. This is all speculation, of course. But it is a problem easily solved by simply using a different, dedicated port for the Ethernet instead of routing it through the display.

However - I am on a Macbook Air M2 and using an OWC Thunderbolt 4 Dock. Currently experiencing WiFi speeds beating the ethernet via the dock connection.

So, that would imply the Dock is running at a lower throughput, like I explained.

Why would the OS think that the connection is USB when it is actually on the Thunderbolt bridge using a Thunderbolt port with a Thunderbolt cable into a Thunderbolt 4 dock.

You can't change a USB device to a Thunderbolt device. The Dock is passing it through via USB. You stated you had a USB to Ethernet, not Thunderbolt to Ethernet. If it is USB to Ethernet, it is only USB. The Thunderbolt Dock may only have USB3 and not USB4. If it worked before through the Dock, ask the people who make the Dock. Sounds like it works fine directly connected to the Mac.

The LG 5K Ultrafine connects to the Mac via a single Thunderbolt 3 connection. How is it not a Thunderbolt hub?

It may be a Thunderbolt hub, but that doesn't make a USB device Thunderbolt. It is still USB if that is what it is.

Also, don't confuse the port shape with the transport protocol. All of Apple's USB-C ports are Thunderbolt, DisplayPort, and USB. When you connect a device, it knows which protocol to use based on what the device tells it. If the device tells it, "hey, bud, I'm USB3," that's the protocol the port will use.

The Thunderbolt Dock is doing the same thing, but it may not support USB4, only USB3. However, since you can connect it directly to your Mac and get USB4 speeds, it seems like your adaptor is USB4 capable, and your Thunderbolt Dock can only do USB3. Or, it may just be the Dock isn't very good.

Yes, there’s no apple hardware because they don’t make a USB-C to Ethernet adapter. They only sell the Belkin one via the Apple Store.

I thought they stopped making it, but here is a Thunderbolt to Ethernet adaptor: Thunderbolt to Gigabit Ethernet Adapter - Education - Apple

Regarding the USB output of built-in hubs, where can I find those ratings?

Here's what could be your Mac: MacBook Pro 14- and 16-inch - Technical Specifications - Apple

But, as I stated, all M1 and later have USB4.

Regardless, just because your Mac can do USB4 doesn't mean a hub you connect to the Mac can handle USB4. It may be Thunderbolt and USB3.

Helpful information -

However - I am on a Macbook Air M2 and using an OWC Thunderbolt 4 Dock. Currently experiencing WiFi speeds beating the ethernet via the dock connection.

Disconnecting all other devices from the dock did not make a difference.

This situation did not start occurring until after the latest OS update to 12.6. The same thing occurred on Big Sur after an OS update.

Why would the OS think that the connection is USB when it is actually on the Thunderbolt bridge using a Thunderbolt port with a Thunderbolt cable into a Thunderbolt 4 dock.

Corrode wrote:

The USB-C to Ethernet adapter is only USB 3 so I disagree that the dock needs to support USB 4 in order to support full throughout.

Regardless, it is a question for the manufacturers of that device. You aren't even using an Apple adapter. No Apple hardware is involved at that point.

Since this is occurring on multiple thunderbolt docks, it seems that the throttling is occurring when the Ethernet data is sent over Thunderbolt. That is the one constant here.

You are referring to that thread from last year. You have to forget about that. Even if that thread were still open, it would have nothing to do with Thunderbolt at all. That display is not a Thunderbolt hub. It is a USB hub. If you had your Belkin adapter plugged in to it, the answer would still be the same.

Your display is also not a Thunderbolt hub. And its USB output isn't even as good as that of the Dell from the other thread.

• it is faster connected directly to the MacBook than to the hub in the display

Then the device is capable of faster speeds and the Hub is not.

the hub is connected via Thunderbolt 3

You can't turn USB into Thunderbolt. USB is synchronous and Thunderbolt is asynchronous. They are two entirely different protocols. If the hub is converting USB to Thunderbolt, that is the likely where the slowdown occurs. It should be passing the USB data straight through as USB.

The way Apple handles USB traffic over Thunderbolt

USB traffic doesn't go over Thunderbolt. It is USB.

I didn’t ask for output specs of the MacBook. I asked for output specs of the hub.

I can't tell you what the specs of the Dell hub are. I have no idea what the model number is to look it up. I had to guess at which 14" MacBook you have. You can search the internet or the specs of the hub.

Clearly Monterey is not treating Ethernet traffic as if it were Thunderbolt -->Ethernet but seems to want to treat it as USB traffic.

Here is a pic of the connections and the resulting Mac OS network screen.

The Mac is a 2022 M2 MacBook Air

Do you have an Ethernet adapter to compare?

Thunderbolt is a protocol that can carry other protocols inside it. For example, when I have an external hard drive connected over a true Thunderbolt connection, then it is difficult to tell that it is running over Thunderbolt. The drive shows up like any other internal drive.