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I would like to connect two computers so that one is connected on physicall via the "standard ethernet jack" (got lost in the naming, i believe it's 8P8C) and the other will be connected to a USB jack.

However, logically they should be communicating via IP.

While searching for the adapters, I realized that I'm not completely clear on the differences between a "Ethernet to USB" adapter and "USB ethernet network card".

  • Is the adapter just physical mapping between the wires? If so, why would it need power and have specific operating system requirements to work. (I found some of those)
  • What is the difference from the OS point of wiew?
  • What is the difference from the users point of wiew? Won't he have a same network interface available ( with ifconfig) in both cases?
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That sounds like 2 different names for the same thing to me. –  Lawrence Dec 19 '13 at 14:05
    
I don't see the difference between the two devices they both perform the exact same function. –  Ramhound Dec 19 '13 at 14:10

2 Answers 2

I don't think there's any difference. You're probably looking at similarly-designed products with different nomenclature. Based on the info you provided, I have no idea what a "USB Ethernet Card" would be insofar as it is distinct from an "Ethernet to USB Adapter".

An Ethernet to USB Adapter is a miniaturized Ethernet chipset inside an enclosure that connects to your computer's USB Host Controller. You can think of it as operating identically to having a PCI Express ethernet card mounted inside the PC chassis, except that the mechanism for communicating between the Ethernet chipset and the motherboard/CPU is USB, instead of PCIe.

If you have one computer which already has an Ethernet card installed in the chassis, and one computer that doesn't, then to connect them over Ethernet (and thus have an IP connection between them), all you need is to buy one Ethernet to USB Adapter and find or buy an Ethernet cable. Then just plug the USB male cable into the computer without an Ethernet adapter, and I think you should know how to do the rest...

I still have no idea what a USB Ethernet Card is, assuming that it is somehow distinct from what I've described above.

To the best of my knowledge, there are no products on the market that don't have "active circuitry" in the Ethernet NIC that's inline with the adapter/cable. If you were simply to map the wires between Ethernet and USB, it wouldn't work. That would be stupid. But don't be fooled by the low price of Ethernet to USB Adapters; 99.9% of them are very likely to be proper Ethernet NICs with all the accompanying circuitry; it's just that their circuitry complexity is not particularly high (especially for ones limited to 100 Mbps speeds), so you don't need a very large or expensive chip to make them.

If you manage to find someone selling adapters that just map the wires between Ethernet and USB, be sure to give their product a bad rating if they're selling it on eBay or Amazon or similar.

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I was thinking the 'usb network card' would use a generic USB host driver (or a proprietary driver) where in the adapter situation the usbnet driver (this is for Linux)? –  Alan Dec 19 '13 at 14:26
    
You still haven't told me what a USB Network Card is, so I have no idea what it would use. Can you link to an actual product? –  allquixotic Dec 19 '13 at 14:27
    
Thank you for pointing it out. I was considering them as cards because of the large price difference. For example, this one is refereed to as a card ebay.com/itm/…. But I've seen them costing 4X more. –  Alan Dec 19 '13 at 14:50
    
....Yeah, that's completely identical to a USB to Ethernet Adapter. –  allquixotic Dec 19 '13 at 14:52
    
They call it an adaptor further down. They're as confused as you are! –  Journeyman Geek Dec 19 '13 at 15:11

There's almost always better alternatives. Unfortunately my last usb -> ethernet adaptor broke so I'm going off memory but

1) There's a specific chip inside that does the interface - in mine, it was a USB-EL1210A made by CATA. (Yes this is an old piece of junk that did half duplex, predating the days of every modern pc coming with ethernet onboard. It was replaced by a PCI card). Modern equivalents would have a different chipset, but they would have a chip. If there's an Ethernet cable at the other end of your adaptor, its clearly not a passive 'electrical' conversion.

2) Assuming you have drivers, it'll be treated the same as another ethernet device, my specific model wouldn't run on anything newer than windows 98 when it came to windows, but ran perfectly fine for a certain value of fine on linux, using the same naming convention as a locally attached ethernet adaptor. They should be reasonably common/generic - though some may need you to compile the driver yourself. Research might be useful here.

These days 'fast' ethernet adaptors are cheap as chips, and there are USB 3.0 gig-e capable adaptors. The raspberry pi HCL might be a useful place if you want ideas on specific adaptors

3) None at all. It'll be detected the same as any ethernet adaptor. I've even had a phone that pretends to be a USB ethernet adaptor and was seen as a eth device if I recall properly.

There is also apparently a way to do ethernet over a physical usb layer but I doubt thats what we're talking about here.

Referring to such a device as a card would be a misnomer - generally when we talk about cards we talk about add on devices on a motherboard, or devices that slot into a express card or pcmcia slot. A USB ethernet device is almost certainly a adaptor or dongle.

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