Ask Lemmy

I guess it doesn't really matter as long as you stick to one for both ends of the cable

It shouldn't actually matter. It's strictly by convention that the US (and probably North America; unclear about beyond) almost exclusively uses B. The big risk is that people will assume it's B, and the other end is B, which can cause issues when they e.g. replace a receptacle and make all of your connections crossover. But even that shouldn't matter much these days.

There's also some very limited issues switching from A to B on the same line (A in wall, B in patch cable), but this is very rare. If you saw A, it was probably either a crossover, or you live in a place that uses A.

So I learned all this almost 2 decades ago so the details may be off...

There's crossover cables, which are a-b and used if you want to connect one computer to another-the tx and rx are flipped from one side to the other, so two "client" devices (like 2 computers) don't speak and listen on the same line

There's rollover cables, which are flipped on one side, that were used to connect to the console port of a router

Aside from that, nothing about the configuration really matters except being standard. The reason they're not just in stripe-color color order is to separate the tx and rx to minimize interference

I'm pretty sure all of this became moot after hundred gigabit Ethernet became a common thing anyways - they multiplex electrical signals across each of the wires, so they have to negotiate the method or fall back to a simpler protocol from the start. I'm not sure how robust it is to randomly shuffling the order on each side individually (I wouldn't try it on hardware I wasn't willing to risk)

So really, all that matters is that it matches. And since we've been doing it a certain way for so long, doing it differently is a bad idea. A vs b makes no difference, but you could make green the split pair and it'd be identical. You could use the same arbitrary order on each side and you'd probably not notice much difference, although you might get a lot more errors from minute interference

And FWIW, I think b is the more common standard across the world... But any advantage or disadvantage probably died back when we stopped using those trunk lines with dozens of pairs split out on a punch down block that goes to a bunch of different homes