Research on Optimal Selection Measurement of DNS Root Instance

DNS root servers are located at the top of the domain name system and are the cornerstone of the Internet. Currently, root servers deploy numerous root instances using anycast technology. Introducing root instances can improve the parsing performance of root servers and the user access experience. However, we found that some root instances do not show optimal performance, and users cannot access the closest root instance when accessing the root instance or even cross-border access. This paper deploys three types of operator detection points in 31 provincial-level administrative regions in mainland China. Each detection point requests the NS record of the top-level domain name from the root instance server introduced in China to obtain the access data of the root instance server hit by domestic users. At the same time, we propose two methods to determine whether users have achieved the optimal choice of root instance, including the method based on the shortest AS path and the method based on geographical distance. In these two methods, we analyze the optimal selection of root instances for each root server. Finally, we analyze the cross-border access of users and find that China Telecom users are more likely to access the root instance across borders.