alt Hacker NewsImagine two computers A and B. A has two NICs, A1 and A2. B has B1 and B2. So 4 NICs total. You connect directly A1 to B1 and A2 to B2 with crossover cables. You then route all the traffic from A to B over A1 to B1 and all the traffic from B to A over B2 to A2.
Why do you do all this? To avoid collisions and the loss of effective bandwidth from back-offs.
It only really works with 2 computers because if you add a 3rd, now you need 12 NICs instead of 4 for unidirectional point-to-point connections.
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But why would you? You don't have collisions since the introduction of full duplex ethernet on both copper/fiber. Kinda sounds like you're confusing half duplex with simplex, or maybe bidi? As a network engineer I've never seen someone ever refer to "simplex ethernet".
That's not how modern ethernet works at all. A single NIC talking directly to an another one has no collisions ever. Depending on what your channel is, either you have separate wires for the directions, or you are using a hybrid circuit (as in telegraphs, the term is so overloaded it's hard to google). Either way, packets going in one direction never wait for packets going in the other.