Towards evaluation of DNS server selection with geodesic distance

Abstract

The DNS (Domain Name Service) is the most fundamental service in the current Internet. Investigating macroscopic performance of DNS server selection algorithm is not an easy task while microscopic software implementations are known. This is mainly because of lack of available performance information (e.g., delay) from authoritative server side. In this paper we estimate the global performance of DNS server selection with passively collected DNS query data at authoritative server. A key idea towards the estimation is to use geodesic path length between authoritative server and cache resolver based on their geolocation information as an approximation of end-to-end delay. We introduce two performance metrics to quantify the efficiency of the server selection: RML (the ratio to the minimum path length) and RBL (the ratio to the best path length). The former corresponds to an additional cost of cache resolver deviating from the minimum path length to the server where the resolver actually accessed, and the latter indicates an extra cost deviating from the best path length to the closest (ideal) server ignoring the complexity of the intra and inter AS level topology. We analyze 1-day long DNS queries from over 700K cache resolvers all over the world to “.jp” TLD servers (JP DNS servers) and demonstrate that 75% of cache resolvers in Japan and 40–60% of cache resolvers in other regions selected the closest server found by their probe, as the most accessed server. Thus, 25% or 60% of cache resolvers could have found a more appropriate authoritative server with a more adaptive selection algorithm. Similarly, 15–35% of resolvers in other regions efficiently accessed the best cost servers as the most accessed server. This means that there is still a room for improvement to reduce the potential delay by change of the infrastructure (i.e., new peering links and deployment of new servers).