Investigating Deployment Issues of DNS Root Server Instances from a China-wide View

DNS root servers are the starting point of most DNS queries. To ensure their security and stability, multiple anycast instances are operated worldwide, and new root instances have been rapidly deployed in recent years. Apart from authorized instances managed by Root Server System, some networks equip unauthorized instances to hijack queries from clients. Despite various root instances handling queries within their residing networks, few studies have focused on the deployment issues of these instances.       In this paper, we provide the first study to reveal the deployment issues of root instances from a nationwide view. With the support of 7,860 vantage points, we utilized a suite of methodologies to identify the deployment of unauthorized instances. 54 vantage points witnessed the evidence of unauthorized instances, and 70.4% of them further observed security issues of unauthorized instances, including DoS, unavailability of DNSSEC validation, and vulnerable DNS software. Additionally, we utilized the side-channel information of censorship mechanisms to measure the catchment area of authorized instances. We found that most authorized instances in the Chinese mainland serve with limited catchment areas due to restricted BGP policies. Through discussions with ISPs and network operators, we make recommendations to improve the deployment status of different root instances.