So it looks like the root namespace providers output a totally reasonable amount of traffic. Divided between the hundreds of points of presence globally, this is tens of megabits per physical host.
This FAQ is illuminating: https://www.verisign.com/en_US/domain-names/internet-resolut...
The servers themselves are ordinary 1 RU physical rack mount servers with 1 Gbps or 10 Gbps Ethernet. Nothing special. I'm guessing that most of the load isn't from the root, e.g.: "j.root-servers.net", but from hosting the authoritative DNS servers for .com and .net (b.gtld-servers.net) on the same box. That would surely have more traffic and much more data.
