Recently I started working on a networking series for software developers who enter the electrical-grid world and suddenly discover that the grid speaks in packets, interfaces, switches, routes, protocols and a suspicious number of acronyms.
Before going anywhere near IEC 61850, utility WANs or substation networks, I wanted to understand the ordinary networking machinery itself. Not only what a switch or ARP does, but why these things had to appear in the first place.
I could start with the OSI model. I have seen that diagram enough times in my life. The problem is that a finished diagram is very good at telling us where something belongs and surprisingly bad at showing why it exists.
So I had a more ridiculous idea.
Imagine that I am somewhere in medieval Europe. No copper cable, no fiber, no radio and definitely no Ethernet. I have stone towers on hills, and the only useful property I can rely on is visibility. If one tower can see another, I can make light visible or hide it.
