[Cerowrt-devel] DC behaviors today

Mikael Abrahamsson swmike at swm.pp.se
Mon Dec 4 07:41:28 EST 2017

On Mon, 4 Dec 2017, Joel Wirāmu Pauling wrote:

> How to deliver a switch, when the wiring and port standard isn't
> actually workable?

Not workable?

> 10GBase-T is out of Voltage Spec with SFP+ ; you can get copper SFP+

Yep, the "Cu SFP" was a luxury for a while. Physics is harsh mistress 

> but they are out of spec... 10GbaseT doesn't really work over Cat5e
> more than a couple of meters (if you are lucky) and even Cat6 is only
> rated at 30M... there is a reason no-one is producing Home Copper
> switches and it's not just the NIC Silicon cost (that was a factor
> until Recently obviously, but only part of the equation).

I have CAT6 in my home, and not more than 30 meters anywhere. So it would 
work for me. You need CAT6e for 100M, so anyone doing new installs should 
use that. Stiff cable, though.

> On the flip side:
> Right now I am typing this via a 40gbit network, comprised of the
> cheap and readily available Tb3 port - it's daisy chained and limited
> to 6 ports, but right now it's easily the cheapest and most effective
> port. Pitty that the fabled optical tb3 cables are damn expensive...
> so you're limited to daisy-chains of 2m. They seem to have screwed the
> pooch on the USB-C network standard quite badly - which looked so
> promising, so for the moment Tb3 it is for me at least.

With that distance, you could probably run 10GE over CAT3 wiring. So there 
is a reason 10GE requires more for longer distances, because it's bad 
cable so instead you need lots of power and DSPs to figure out what's 
going on.

Mikael Abrahamsson    email: swmike at swm.pp.se

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