I think parent means: there no network protocol which can propagate blocking in sane manner between providers (something like bgp for firewalls) edit: yes, you

I think parent means: there no network protocol which can propagate blocking in sane manner between providers (something like bgp for firewalls) edit: yes, you can you bgp to blockhole subnet traffic - the standard doesn't play well if you want blackhole unrelated subnets from upstream network