Measuring Query Latency of Top Level DNS Servers
We surveyed the latency of upper DNS hierarchy from 19593 vantage points around the world to investigate the impact of uneven distribution of top level DNS servers on end-user latency. Our findings included: 1) generally top level DNS servers served Internet users efficiently, with median latency 20.26ms for root, 42.64ms for .com/.net, 39.07ms for .org; 2) quality of service was uneven, Europe and North America were the best while Africa and South America were 3 to 6 times worse; 3) most of the root servers performed well in Europe and North America, but only F, J, L roots showed low query latency in other continents; 4) query latency of F and L roots showed that only about 60 resolvers were routed to the nearest anycast instances. We also revealed two problems that lead to constantly large query latency (6s~18s) for resolvers. One was buggy implementation of some resolvers on IPv4/IPv6 dual-stack hosts, the other was misconfigured middle-boxes that filtered large or fragmented DNSSEC packets.
KeywordsMedian Latency Open Resolver Domain Name System Authority Server IPv6 Address
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