[lmm]

> Ethernet is a pretty simple physical-layer protocol only made for 1:1 connections, and you can't generally inject packets from a simple tap mid-cable.

This is complete nonsense. Ethernet is a shared-medium protocol. The fact that it doesn't need any special handling of particular endpoints is one of the things that distinguishes it from e.g. Token Ring. How do you think it's possible to link two switches with a standard cable on standard ports? What on Earth are you basing your claims on?

[pclmulqdq]

Ethernet as used in almost every facility has not practically been a shared-medium protocol for decades. The citation of "token ring" sort of dates your notion of "Ethernet."

The Ethernet spec is over 5,200 pages, including the old multi-drop buses, but the parts of the standard that specify the physical layer and actually get used, including 10/100/1GBASE-T and the fiber Ethernets, cannot support more than one endpoint on a wire.