A hierarchy of caches is not the core idea. This is a common misunderstanding, but it is not how the DNS works. There is a hierarchy of content, content DNS s

A hierarchy of caches is not the core idea. This is a common misunderstanding, but it is not how the DNS works. There is a hierarchy of content, content DNS servers serving up their portions of the overall DNS database with delegations pointing to subdomain content DNS servers, and resolving proxy DNS servers stitching all of this content together (combining a bunch of partial answers from different content DNS server into an overall full answer) as they perform query resolution. Content DNS servers don't even have caches, as they serve up content directly from some kind of back-end database source. That is the core idea; distribution of content around the world's content DNS servers, rather than having a giant replicated /etc/hosts or HOSTS.TXT file. Indeed, the headlined interview begins with this very point. And yes, there has been at least one significant change in implementation. It was about a quarter of a century ago, when people began to realize that not having the same single DNS server perform multiple rôles was a good idea, and indeed best practice, and the whole RD/AA thing turned into mostly a hangover from old poorer practices. So if you were about to retort that some content DNS servers (e.g. ISC's BIND, Microsoft DNS server) also doubled up as caching proxy DNS servers and did have caches, you should notice that even the "Cricket" Book has been recommending proper separation of rôles for many years now. This was a major change, reflected in the designs of newer DNS softwares than ISC's BIND, such as Bernstein djbdns, MaraDNS, PowerDNS, and nsd, which do not mix the rôles in a single program. And it's page 321 et seq. in the 2001 edition of the book. * http://jdebp.uk./FGA/dns-server-roles.html http://jdebp.uk./FGA/dns-server-roles.html