AFAIK a whole lot of cat herding at the level of ISPs and peering administrators and an upgrade of things like BGP. Very hard to do coordinated updates to a fed

AFAIK a whole lot of cat herding at the level of ISPs and peering administrators and an upgrade of things like BGP. Very hard to do coordinated updates to a federated network, as IPv6 shows... we are 20+ years in and the IPv6 transition is still only crawling along.