USB Ethernet fast and reliable?

phunni · 2015-07-21 14:39:20

Apologies for any typos, I'm writing this on my phone.

I'm having serious problems with the nic on the box that acts as my router. The issue sends to be either the card itself or a dodgy connector on the mobo. I can't be certain, but I suspect the latter.

I'm considering buying a new NIC, but given that the slot is not pci express, although most new cards seem to be, as well as the fact that it could be the mobo, I'm tempted to buy a USB Ethernet adapter. Please note, in case it isn't obvious, I'm talking about a wired connection here.

My questions therefore are:

1) what's the Linux support like for USB Ethernet?
2) Would a USB adapter be as fast and reliable as a pci one?

This would be the link to my home network from my router, so I need it to be reliable.

ewaller · 2015-07-21 14:50:25

I've found it to be well supported and reliable. Fast? If you are on USB 2.0, you are going to top out around 280Mbits/sec. Fast enough for 10/100 Base-T. Not good enough for 1000 Base-T.

I've not every tried SuperSpeed USB 3.0 devices. The bus speed would support gigabit rates, but I've no idea if they are available or supported.

phunni · 2015-07-21 15:11:10

I'm not sure if the box supports USB 3 to be honest, but it's faster than my internet, so it should be fast enough I suppose!

phunni · 2015-07-21 16:04:16

Have just determined via "lsusb" that I have one 2.0 port and a number of 1.1 ones. How do I figure out which is which?

ewaller · 2015-07-21 16:17:11

Plug a device into a port and rerun lsusb. The device will enumerate and lsusb will tell you which bus number it is on. Look for the root hub with the same bus number and that will tell you.

phunni · 2015-07-21 16:21:46

Brilliant - thank you!

phunni · 2015-07-21 16:24:20

Apologies if this is a stupid question - I'm still thinking all this through. Given that an ethernet port via USB wouldbe faster than my internet, but (probably) slower than my other (on board) ethernet, would it not make sense for me to use the USB one for the internet connection and the on board one for the internal network connection?

mich41 · 2015-07-21 17:58:36

I have a UNITEK Y-3461 USB 3.0 gigabit interface. I never used it 24/7, but it worked well for copying some multi-GB files for several hours at USB 2.0 speed. It reaches 30-40 MB/s on USB 2.0 and, IIRC, reasonably close to 1Gb/s on 3.0.

Avoid the cheapest dongles marketed as "full speed usb 2.0" or something like that, here "full speed" means 12Mb/s and being USB 2.0 compliant doesn't require the device to support any faster rate.

However, personally I'd just grab some old rtl8193 PCI card for a beer or two and be done with it.

ewaller wrote:

Plug a device into a port and rerun lsusb. The device will enumerate and lsusb will tell you which bus number it is on. Look for the root hub with the same bus number and that will tell you.

Oh c'mon, the OP has a dual stack and every low/full speed device will be routed to one of these UHCIs and every high speed device to the EHCI, no matter which port you use.

@UP: yes, I guess it would.

Last edited by mich41 (2015-07-21 18:00:14)

ewaller · 2015-07-21 18:17:10

mich41 wrote:

Oh c'mon, the OP has a dual stack and every low/full speed device will be routed to one of these UHCIs and every high speed device to the EHCI, no matter which port you use.
@UP: yes, I guess it would.

Is that true? If so, Clearly I have missed something fundamental

Edit: Are you talking 2.0/3.0 ? Or are you talking 1.1 / 2.0 routing?

Edit: Certainly, if a device is plugged into a 2.0 hub, it will use the appropriate stack. But I believe that if you plug into a USB 1.1 hub, you get 1.1 only. Again, unless I am missing something.

Last edited by ewaller (2015-07-21 18:30:46)

Gusar · 2015-07-21 19:26:29

@ewaller: Old machines needed an USB 1 controller per port, but a single USB 2 controller for all the ports. And I'm talking about the same ports here, not on separate hubs. So it's exactly how mich41 describes it, no matter where you attach your device, it'll be handled by the appropriate controller.

@phunni: I'd get a PCI card. They're still around, even gigabit ones. PCI can theoretically handle it, don't know about practice. But even if it can't handle the full gigabit, I believe it'll be faster than an USB 2 adapter. An USB adapter will work perfectly fine, but USB has a lot of overhead. Which not only means performance in practice is lower than USB's theoretical limits, CPU usage will also be higher than with a PCI card.

phunni · 2015-07-21 19:30:53

@gusar my concern about a pci card (apart from finding a compatible one) is that the problem might actually be the socket itself.

Thanks guys, for all the help - very useful.

Gusar · 2015-07-22 12:53:23

@mich41: A question - when you plug your USB3 adapter into an USB2 port, does it work in gigabit ethernet mode or fast ethernet mode?

phunni · 2015-07-22 13:02:25

Gentlemen (and/or ladies) thanks for your help. An Anker USB adapter arrived this morning and is working well. I appear to be getting around the same internet speeds as I was before - so I'm happy :-)

Last edited by phunni (2015-07-22 13:02:40)

mich41 · 2015-07-22 20:57:33

Gusar wrote:

@mich41: A question - when you plug your USB3 adapter into an USB2 port, does it work in gigabit ethernet mode or fast ethernet mode?

Mine works in gigabit mode and generally any adapter has no sensible reason not to.

ewaller · 2015-07-22 21:45:03

mich41 wrote:

Mine works in gigabit mode and generally any adapter has no sensible reason not to.

Except you cannot maintain gigabit rates on USB 2.0, so it will have to slow down, even though it is 1000 Base-T mode (using 4 pairs on Cat 5 cable instead of 2)

Gusar · 2015-07-23 01:02:54

ewaller wrote:

Except you cannot maintain gigabit rates on USB 2.0, so it will have to slow down, even though it is 1000 Base-T mode (using 4 pairs on Cat 5 cable instead of 2)

You can't get the full gigabit because USB2 is 480 mbit/s, but there's still a difference between fast ethernet (100 mbit/s) and going as fast as the bus will handle in gigabit ethernet mode. I'm not sure why, but I thought these adapters will only work in fast ethernet mode when connected to USB2.

Last edited by Gusar (2015-07-23 01:12:04)

Arch Linux

#1 2015-07-21 14:39:20

USB Ethernet fast and reliable?

#2 2015-07-21 14:50:25

Re: USB Ethernet fast and reliable?

#3 2015-07-21 15:11:10

Re: USB Ethernet fast and reliable?

#4 2015-07-21 16:04:16

Re: USB Ethernet fast and reliable?

#5 2015-07-21 16:17:11

Re: USB Ethernet fast and reliable?

#6 2015-07-21 16:21:46

Re: USB Ethernet fast and reliable?

#7 2015-07-21 16:24:20

Re: USB Ethernet fast and reliable?

#8 2015-07-21 17:58:36

Re: USB Ethernet fast and reliable?

#9 2015-07-21 18:17:10

Re: USB Ethernet fast and reliable?

#10 2015-07-21 19:26:29

Re: USB Ethernet fast and reliable?

#11 2015-07-21 19:30:53

Re: USB Ethernet fast and reliable?

#12 2015-07-22 12:53:23

Re: USB Ethernet fast and reliable?

#13 2015-07-22 13:02:25

Re: USB Ethernet fast and reliable?

#14 2015-07-22 20:57:33

Re: USB Ethernet fast and reliable?

#15 2015-07-22 21:45:03

Re: USB Ethernet fast and reliable?

#16 2015-07-23 01:02:54

Re: USB Ethernet fast and reliable?

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