Measuring the Placement of DNS Servers in Top-Level-Domain

DNS is a critical infrastructure of the global Internet. To assure DNS’s efficient and robust operations, each domain, especially each of the Top-Level-Domains (TLDs), should deploy multiple redundant nameservers in diverse locations. To assess the robustness of TLD nameserver deployment regarding the nameserver redundancy and location diversity, we conduct a measurement study by sending special DNS queries and running traceroute to TLD nameservers from about 200 PlanetLab sites. By combining the measurement data with other data sources including IP address assignment, BGP routing tables, and IP address location inference, we identify the nameserver providers for all TLDs and the locations of their servers. Our results suggest that TLD nameservers are adequately distributed as of today, more than 90% TLDs can survive from single point failure. We also observe that many TLD nameservers are co-located at a small group of “hot spots”. We conduct simulations to evaluate the impact of such co-locations. Our results show that failure of single hot spot does not affect robustness of TLD services.