IP geolocation databases

TLDR

IP geolocation relies on databases that map IP blocks to geographic locations, yet these widely used resources are often unreliable and biased toward a few popular countries. The authors compare several commercial and free geolocation databases to identify usability limitations. They evaluate database accuracy using ground‑truth data from a large European ISP, quantifying the impact of fine granularity on performance. The study finds that most database entries cover only a few countries, misrepresent IP allocation and BGP announcements, and that fine granularity actually degrades accuracy, limiting claims to country‑level rather than city‑level precision.

Abstract

The most widely used technique for IP geolocation consists in building a database to keep the mapping between IP blocks and a geographic location. Several databases are available and are frequently used by many services and web sites in the Internet. Contrary to widespread belief, geolocation databases are far from being as reliable as they claim. In this paper, we conduct a comparison of several current geolocation databases -both commercial and free- to have an insight of the limitations in their usability. First, the vast majority of entries in the databases refer only to a few popular countries (e.g., U.S.). This creates an imbalance in the representation of countries across the IP blocks of the databases. Second, these entries do not reflect the original allocation of IP blocks, nor BGP announcements. In addition, we quantify the accuracy of geolocation databases on a large European ISP based on ground truth information. This is the first study using a ground truth showing that the overly fine granularity of database entries makes their accuracy worse, not better. Geolocation databases can claim country-level accuracy, but certainly not city-level.