Bandwidth is symmetrical, control is not [LWN.net]

Bandwidth is symmetrical, control is not

Posted Jun 12, 2009 18:38 UTC (Fri) by khim (subscriber, #9252)
In reply to: Linux first to offer USB 3.0 driver (Linux Devices) by Steve_Baker
Parent article: Linux first to offer USB 3.0 driver (Linux Devices)

I think it's very likely the bandwidth is symmetrical. I have not read anything to suggest it is otherwise at least.

Badwidth is symmetrical, but like all version of USB there are devices and there are hosts. PC is a host, HDD is device and some cams can be both (host when connected to printer, device when connected to PC). Since difference between host and device is fundamental you can not just connect two PCs via USB - you need connecting device. Device like this one can act as mediator, but all such devices have poor, unreliable and, most importantly, slow drivers and in general it makes USB unusable as network solution... Certainly not threat to Ethernet...

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Bandwidth is symmetrical, control is not

Posted Jun 12, 2009 20:35 UTC (Fri) by Steve_Baker (guest, #265) [Link]

If the 3.0 controllers support the USB On The Go (OTG) extension, it might
not be a problem (although it may still require a special cable for
electrical reasons,) otherwise I suppose PC to PC USB would continue to
require a bridge chip. A bridge chip can probably be made decently fast,
but would still introduce latency. Since 3.0 allows for slave initiated
communications I suspect a bridge chip will be unnecessary. Furthermore
the spec seems to specify a special A to A cable for debugging and "other
host-to-host connection applications." I'm cautiously optimistic as it
really seems like 3.0 is taking on Firewire which has always had this
capability.

As far as the network topology goes, at the USB level it would just be a
point to point link, one end a host/master, the other a device/slave. The
mesh network wouldn't be handled at the USB protocol layer, but at a
higher layer.

I'm not saying it's going to work the way I'd like, just that it might,
I'm keeping my fingers crossed.