File sharing using USB cable?

[lugoteehalt]

Sorry if this a bit simple, but can I simply connect two (that's 2) computers via some sort of USB cable and move files between them? What do I ask the nice lady at the shop for?

TIA.

[saikee]

You know what? You have me fooled.

I actually overturned my drawers, found a USB cable with two male ends, switched on two PCs, booted up two Linux and hooked the cable to a USB port on each PC.

Result -------------------------------------------------------

Nothing.

Then I thought the guy who invented the USB ports must have tried this out before himself. If the two PC could talk through a USB cables then we would be able to throw away the network cards. Would he not have shouted it out so loud that every PC user would have heard it.

In conclusion

It looks like the standard distros don't allow one PC talks to another PC via a USB cable. May be this is technically impossible. If it is possible then may be it is a nice project for some enthusiastic PC users.

[michaelk]

You can possibly damage your computers by connecting a regular USB cable to two computers. You are basically shorting 5 VDC. It will not work because you can not directly connect two controllers together and in addition there are +/- signals so you basically need a crossover connection.

However, there are special USB data transfer cables that you can find just about in any electronic store. (MS hypes these for upgrading and transfering apps and data) The usbnet module basically configures a virtual ethernet port where you can assign an IP address. I do not know which chipsets are support with the usbnet module. Check linux-usb.org for information and of course google.

http://www.usbgear.com/computer_cable_details.cfm?sku=CANET103&cats=160&catid=508%2C106%2C141%2C508%2C106%2C141%2C112%2C16 0

[saikee]

It did cross my mind about the the 2 out 4 wires in a USB has a 5VDC power supply. However I had more faith in the short circuit protection of the PC components.

Checked the PC afterward and the port still works. I wouldn't press my luck to try it again though.

[bwkaz]

USB on its own is an asymmetric protocol: you have one master, talking to up to 127 slaves. You can only ever have one master. Each computer's USB controller is a master, so you can't hook multiple computers up to each other via USB.

However, the Linux kernel has "USB gadget" drivers, which make your Linux machine into a USB printer-class, or storage-class, or whatever, device. So if you have a USB client chip somewhere (most machines don't, but lots of embedded devices do), you could drive it and act like a storage class device, exposing some or all of your filesystem over the USB link. But you need the hardware first. :)

As far as the data transfer cables: I would suspect that these are USB -> NIC -> second NIC -> USB bridges, all wrapped up in a single cable. The actual link is probably Ethernet (especially if you're using the usbnet module), and you get two different USB device chips, each plugging into their own USB host.

[i845_]

I actually overturned my drawers, found a USB cable with two male ends, switched on two PCs, booted up two Linux and hooked the cable to a USB port on each PC.

:eek: :eek: :eek:

My friend tried that once... and as michaelk has rightly pointed out, he ended up nuking one of his mainboards!

@lugoteehalt

Basically look out for A-to-A cables that have a chip in between. These are also known as USB 'bridge' cables. It is the chip that does the magic involved (so far as I know...). They should look like these (http://www.shivaranjan.com/shivaupload/windowslivewriter/10WaystoNetworkTwoComputers_11F65/usbbridgecable.jpg)...

Read this (http://www.hardwaresecrets.com/article/248) for more info.

@bwkaz

The actual link might not be Ethernet after all: these cables offer a max. transfer rate of upto 480 Mbps (USB 2.0).

Fast Ethernet, Gigabit Ethernet and 10 Gigabit Ethernet offer max. transfer rates of upto 100 Mbps, 1 Gbps, and 10 Gbps respectively...

[lugoteehalt]

Thanks girls - that seems to basically sort it. The shop lady refused to sell me anything saying she only had stuff for microsoft - don't quite know what to make of this. Thanks again.

[bwkaz]

The actual link might not be Ethernet after all: these cables offer a max. transfer rate of upto 480 Mbps (USB 2.0).

Fast Ethernet, Gigabit Ethernet and 10 Gigabit Ethernet offer max. transfer rates of upto 100 Mbps, 1 Gbps, and 10 Gbps respectively... Not if you're using USB2 to talk gigabit, they don't. The network link can handle gigabit, but the USB2 link on the other side of the bridges can only handle 480Mbps, so that's all that you actually get. The slowest link in the chain determines the speed of the whole chain. ;)

So I'd guess that they're using a USB2 -> gigabit chipset -> gigabit chipset -> USB2 type setup. :)

It may be pure USB2, as you said, but if it uses the usbnet driver, then I doubt it. ;)

[i845_]

The slowest link in the chain determines the speed of the whole chain.

That did cross my mind more than once.

Let's look at the setup you mentioned:

USB 2.0 +----+ 10/100/1000 +----+ 10/100/1000 +----+ USB 2.0

Gigabit Ethernet interfaces are capable of rates upto 1 Gbps. The USB interfaces act as bottlenecks in this case, restricting the speed to only 480 Mbps (as you mentioned...)

Again,

USB 2.0 +----+ 10/100 +----+ 10/100 +----+ USB 2.0

Here the Fast Ethernet interfaces shall act as bottlenecks, restricting the speed only to 100 Mbps (although the OS will register the connection as having a speed of 480 Mbps anyway...)

In both cases, one ends up with something that fails to utilize the interface(s) involved to their fullest... that's what appears weird to me. :confused: :confused: :confused:

It's time for some Googling, I guess...

[rdeschene2]

"The slowest link in the chain determines the speed of the whole chain."

Yep, the old "rate limiting step" applies to data connections as well as chemical reactions and manufacturing lines. If you think of pipes of different sizes feeding into each other, you quickly realize that the rate limiting factor is the pipe with the smallest outlet and if you try to pour more in then that, things just get backed up.

Caches are just replacing the pipes with funnels (with lids!) so they can absorb some funnels running a bit faster than others, at least occasionally.

[.iznogud]

Hi all.. just to digress a bit 'bout bottleneck:

CAT-5 cables are rated with 100Mbps of throughput,
CAT-5e goes with 350Mbps,
CAT-6 comes with a gigabit of throughput.

CAT-6 cables are made of solid wire, i've never seen it made of stranded wire, and each line has to be in a separate sleeve, thus making it really robust, and in no means "useful" between two USB ports. CAT-6 is not standardized and very often it is incompatible with CAT-5e connectors, etc.

therefore, such link would be rated with max throughput of 350 mbps in case it was built on ethernet with usb chips at the ends.

p.s. lol @ myself - I came here looking for some tips and help, and here is my first post - being smart455

[bwkaz]

CAT-5 cables are rated with 100Mbps of throughput, Per pair...

CAT-5e goes with 350Mbps, Not really, at least not throughput. That speed is the absolute minimum-allowable maximum baud rate per pair: there are two sets of two pairs in a cable, and there are lots of reasons that the baud rate may not equal the data throughput rate (the biggest would be if the 1000BaseT standard specified compression of the data).

Plus, a cable can be made to a higher spec than cat5e, but not be certified for cat6 for any of several reasons -- if so, then the cable will be able to handle higher baud rates. But there's nothing in the Category 5E standard that prevents cable from being able to handle higher baud rates.

CAT-6 comes with a gigabit of throughput. And again, per pair.

CAT-6 cables are made of solid wire, ... Irrelevant?

and in no means "useful" between two USB ports. Not directly, you're right there. Since USB uses four wires (+5V, GND, D+, D-), while Ethernet uses eight wires (RX+, RX-, TX+, TX-, plus four unused wires for 100BaseT, or another set of RX+/RX-, TX+/TX- for 1000BaseT), you're right that an Ethernet-type wire isn't useful between USB devices.

But that wasn't what we were talking about, either. ;) We were talking about a single device with two USB male type A plugs, which has (between the USB plugs) a pair of Ethernet transceivers hooked together. The transceivers can both be held inside a single enclosure and hooked up to each other directly, requiring absolutely no Ethernet-type cable of any kind. They can even be close enough to not require any twisting in the wires: think two chips right next to each other on a single board, with eight traces between them that are each about a millimeter long. (Of course that would require a custom pair of chips, so the transmit pins hook up to the receive pins. A standard chip could be used with a bit of trace monkeying, making the traces maybe a few tens of millimeters long.)

Since the bandwidth claimed by the manufacturer is 480mbps, gigabit Ethernet devices would make sense, because then the bandwidth limiter would be the USB bus.

CAT-6 is not standardized and very often it is incompatible with CAT-5e connectors, etc. Maybe several years ago it wasn't standardized. Not anymore. EIA/TIA most definitely has a Category-6 cable standard: see, for instance, this (http://www.lanshack.com/cat5e-tutorial.aspx). And note the bandwidth figures given there, as well.

As far as it being "incompatible" with cat5e connectors, everything uses the same pinout. The only possible way it could be incompatible is if it used a different pinout: that's just not the case. Now, maybe cat5e connectors made the entire run of cable only be usable at cat5e specs, but that's different from being incompatible.

therefore, such link would be rated with max throughput of 350 mbps in case it was built on ethernet with usb chips at the ends. Nope. For one, if that was true, then absolutely every single gigabit link (using cat5e cable) would actually have a data rate of 350mbps. It doesn't: the data rate is a gigabit per second.

Second, just because this type of USB device has two gigabit transceivers does not necessarily mean that they're connected with cat5e cable.

Third, even if the devices were connected with cat5e cable, the maximum data rate between the transceivers would still be 1gbps, not 350mbps.

[.iznogud]

well excuse me for being shallow (hence the nickname) :) i better shut up :)

[Satanic Atheist]

My tuppence worth:

I'm using Cat-5e cable in my house but I've wired and crimped on all the modules at the end (since the network is physically built into the house with wall-plates and everything) and I can run at Gigabit speeds. The switch registers that my laptop is running at 1Gbps (green light) and my router at 10/100Mbps speeds (orange light). I've successfully connected another 1Gbps computer to the network and tried copying something huge over it and it does appear to be able to use all the bandwidth (although this was well over a year ago now, I can't remember the details). The only reason I don't use my server on Gigabit Ethernet is because the driver is broken for running at that speed.

So does this mean that I have good-quality Cat-5e cable (and can hence run at Gigabit speeds) or my gear is lying to me?

James

[bwkaz]

So does this mean that I have good-quality Cat-5e cable (and can hence run at Gigabit speeds) or my gear is lying to me? My guess? Your equipment isn't lying. Depends on the bandwidth that you saw, though: Was it up above 100mbps? (That's 12.5 megabytes per second. Though I see in the other thread that you already know that. :))

If it was anything above 12.5 megabytes/sec, then yes, you were running at gigabit. Well, unless it wasn't Ethernet (token-ring or some crazy serial OC3 or something would be different speeds).

[Satanic Atheist]

Hehe. I wasn't running token ring or anything crazy like that (I live in the here and now, not the yesterday!) but I honestly can't remember the speed that it was running at. I doubt that it would make a huge amount of difference, though since the hard drives would be the bottleneck in this case.

I might try knocking up a RAM disk on each machine and trying the server in Gigabit mode (again) and seeing how fast I can transfer data...

I'm still a bit surprised that my Cat-5e cabling can support Gigabit Ethernet since it's not specced for it... but I suppose it's perfectly possible (just because it isn't rated for it doesn't mean it won't work - ever used a nail as an emergency fuse?).

James

[bwkaz]

I'm still a bit surprised that my Cat-5e cabling can support Gigabit Ethernet since it's not specced for it... But, see, that's the thing. It is specced for it. See the link above, reproduced here (http://www.lanshack.com/cat5e-tutorial.aspx). :p

[Satanic Atheist]

Oops. Missed that link! Thanks. OK, I get it now - it should've been running at Gigabit speeds. Now, if only I can fix the Gigabit port on the server (broken driver) I'll have the entire network running at Gigabit speeds! It is quite annoying that the main point of the network (the server) is the bottleneck...

James