This really brings back some memories. My first career in IT was supporting and implementing an OS/2 Lan Server based banking implementation for a regional bank in the south. The bank deployed what was essentially a massive flat token ring based network interconnected via Fiber to regional areas and leased lines to branches. It was not Netbios over TCP/IP, it was straight up Netbios over the entire network. Given Netbios is broadcast based for resolution, broadcast storms were common across the network, so a gordian knot of filters and configs were setup at the routers to mitigate this. There was no concept of subnet based routing implemented yet.

I ended up taking a job with IBM supporting the TCP/IP stack on top of OS/2. It was a 24 year old me, and a grey beard 60 year old dude that literally supported the entire OS/2 Lan Server TCP/IP stack across the world during the time that corporate networks were just beginning to connect to the Internet. Everyone else on the OS/2 support team at IBM just punted to us anything that was TCP/IP related and thought we were wizards or something. What a wild time to be alive.