In this episode of PING for 2025, APNIC’s Chief Scientist, Geoff Huston returns to the Domain Name System (DNS) and explores the many faces of nameservers behind domains. Up at the root (the very top of the namespace, where all Top-Level Domains (TLDs) like .gov, .au, or .com are defined), there is a well-established principle of 13 root nameservers. Does this mean only 13 hosts worldwide service this space? No. Thousands of hosts act as one of those 13 root server labels, in a highly distributed worldwide mesh known as ‘anycast‘, which works through BGP routing.
The number of nameservers assigned to a domain and how resolvers (the systems that query authoritative nameservers) choose which one to use are not as clearly defined as you might expect. While aspects like packet sizes, data order, and encoding are strictly specified, the process of selecting and consistently using a particular nameserver for similar queries is largely undefined.
Geoff has been using the APNIC Labs measurement system to study resolver behaviour, focusing on basic statistics for delegated domains at the root. He has observed significant variation in the number of nameservers, their diversity, and their deployment methods in routing. More notably, the way resolvers choose which nameserver to use suggests that many still rely on outdated and overly simplistic selection methods.
Read more about Geoff’s research on DNS nameserver selection and diversity on the APNIC Blog:
- DNS nameservers: Service performance and resilience (February 2025)
- DNS nameservers (December 2024)
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