Comment by cyberax

And for a while, telco engineers tried to retrofit Internet to their purposes.

I worked on a network that used RSVP ( https://en.wikipedia.org/wiki/Resource_Reservation_Protocol ) to emulate the old circuit-switched topology. It was kinda amazing to see how it could carve guaranteed-bandwidth paths through the network fabric.

Of course, it also never really worked with dynamic routing and brought in tons of complexity with stuck states. In our network, it eventually was just removed entirely in favor of 1gbit links with VLANs for priority/normal traffic.