I disagree with the overall point you're making here, but I can see that you are seriously committed to it, so I think that no amount of examples of internetwor

I disagree with the overall point you're making here, but I can see that you are seriously committed to it, so I think that no amount of examples of internetworks from the 1980s and 1990s is going to persuade you: to you, I think they'd all be toy-scale and thus irrelevant. Networking in the 1980s and early 1990s was all small LANs, for the vast majority of users, and for PC-type kit. But there were internetworks, yes. DEC ran a global network; DEC tech support was my first experience of true worldwide follow-the-sun support, where the techs on 3 different continents could pick up my case from a single shared database and help me move it forward. I was sysadmin of the London node of a DECnet internet that spanned Oslo, Copenhagen, Stockholm and Helsinki. No IP links between the sites, just DECnet. Companies were running global IPX internetworks: that is how the problems with scaling Netware 3's bindery database arose, which is why Novell developed NDS and Netware 4. Yes, it was a thing. Updating and modernising it was hard.