Measuring the Global Recursive DNS Infrastructure: A View From the Edge

The Domain Name System (DNS) is one of the most critical Internet subsystems. While the majority of ISPs deploy and operate their own DNS infrastructure, many end users resort to third-party DNS providers with hopes of enhancing their privacy, security, and web performance. However, bad user choices and the uneven geographical deployment of DNS providers could render insecure and inefficient DNS configurations for millions of users. In this paper, we propose a novel and flexible measurement method to (1) study the infrastructure of recursive DNS resolvers, including both ISP's and third-party DNS providers' deployment strategies; and (2) study end-user DNS choices, both in a timely manner and at a global scale. For that, we leverage the outreach capacity of online advertising networks to distribute lightweight JavaScript-based DNS measurement scripts. To showcase the potential of our technique, we launch two separate ad campaigns that triggered more than 3M DNS lookups, which allow us to identify and study more than 76k recursive DNS resolvers giving support to more than 25k eyeball ASes in 178 countries. The analysis of the data offers new insights into the DNS infrastructure, such as user preferences towards third-party DNS providers (namely, Google, OpenDNS, Level3, and Cloudflare recursive DNS resolvers account for ~13% of the total DNS requests triggered by our campaigns), and into deployment decisions of many ISPs providing both mobile and fixed access networks to separate the DNS infrastructure serving each type of access technology.