A considerable portion of SDN craze involved pretty much this. Even systems that didn't use OpenFlow were incredibly chatty, creating complex chains of NextHop

A considerable portion of SDN craze involved pretty much this. Even systems that didn't use OpenFlow were incredibly chatty, creating complex chains of NextHop routes from centralized or at least semi-centralized servers to the actual switches. Even in more sane setups, it's not actually uncommon to have control plane talk over network to actual forwarding plane - IIRC Cisco Nexus operates this way, with actual forwarding engines talking with control plane over Ethernet link. I like the code to run on the switches directly, but SDNs very often eschewed that for dumber forwarding engines controlled OpenFlow way, even if actual protocols used weren't OpenFlow.