ISPs’ duplicate DNS queries could strain resolvers, ICANN warns

ICANN says some internet service providers are generating unusual volumes of DNS traffic by sending each customer query to three separate resolvers. The practice appears intended to improve resilience, but DNS systems are already designed to cope with resolver failures, and unnecessary duplicate requests could add strain if adopted widely.

The finding comes from ICANN’s monitoring of DNS stability and resilience. Researchers say the ISPs send queries over both IPv4 and IPv6, with about half of uncached requests repeated within 100 milliseconds and a further 30 per cent within 30 seconds. Separately, Chrome’s share of DNS root server traffic has fallen from 45 per cent to about one per cent after Google addressed a browser flaw; ICANN also estimates users can now see just under 150 resolver farms, down from nearly 250 in 2020.