Longitudinal Analysis of Root Server Anycast Inefficiencies

Anycast is widely used in critical Internet infrastructures, including root DNS servers, to improve their scalability, resilience, and geographic proximity to clients. In practice, anycast depends on interdomain routing to direct clients to their “closest” sites. As a result, anycast’s performance is largely a result of available BGP routes. We provide what we believe to be the first longitudinal study of how anycast performs in providing load balancing and geographic proximity. We examine about 400M queries per day collected from over 100 anycast sites of the D root DNS server for over a year. From this data, we find evidence of excessively unbalanced load: several anycast sites absorb the majority of the total traffic. Moreover, we find that most of the clients do not use geographically proximal sites; queries on average travel twice the minimum distance. To investigate the root cause of these inefficiencies, we use more than 9,000 probes in RIPE Atlas to measure 9 out of 13 DNS root servers. We show two main causes for poorly balanced load and long query distance: insufficient peering between the hosting domain and large ISPs, and misconfigured routes, often due to route leakages, from ISPs with poor