[2023.01.17] Measuring DNS-over-HTTPS Performance Around the World

ABSTRACT

In recent years, DNS-over-HTTPS (DoH) has gained significant traction as a privacy-preserving alternative to unencrypted DNS. While several studies have measured DoH performance relative to traditional DNS and other encrypted DNS schemes, they are often incomplete, either conducting measurements from single countries or are unable to compare encrypted DNS to default client behavior. To expand on existing research, we use the BrightData proxy network to gather a dataset consisting of 22,052 unique clients across 224 countries and territories. Our data shows that the performance impact of a switch to DoH is mixed, with a median slowdown of 65ms per query across a 10-query connection, but with 28% of clients receiving a speedup over that same interval. We compare four public DoH providers, noting that Cloudflare are excels in both DoH resolution time (265ms) and global points-of-presence (146). Furthermore, we analyze geographic differences between DoH and Do53 resolution times, and provide analysis on possible causes, finding that clients from countries with low Internet infrastructure investment are almost twice as likely to experience a slowdown when switching to DoH as those with high Internet infrastructure investment. We conclude with possible improvements to the DoH ecosystem. We hope that our findings can help to inform continuing DoH deployments

-jhsong