Comment by wrs

I'm talking about data not able to leave the building, not even data getting lost on the way.

One example was a site that had fiber and coax, from different companies. They might have shared a pipe at some point along their length, hard to say. But both connections went down at the same time for digital reasons, not physical. The providers had simultaneous unrelated backend router problems and the site lost contact to both gateways.

This was with a nice SD-WAN system that routed everything dynamically across both pipes to address latency and errors, but if the packets get dropped at the first hop in both networks, there's not much you can do!

The saving grace in that case was the third redundant connection, a 4G cell modem, with a lot less bandwidth but able to keep the critical transactions going. These days I'd certainly want Starlink on the roof as well.