Who is whois? An analysis of results consistence

Mapping an IP address to the Autonomous System announcing it is a key feature in network monitoring, and - as a consequence - in network management and research. An informed choice of the tool to use and of the database to query, is of extreme importance for the consistence of the obtained results. In this paper, we evaluate the reliability of the whois tool and the consistence of its results while querying different databases. In particular we show how, on average, more than one third of the whois queries return a minority answer or no answer, while a single database returns a minority answer or no answer in more than 10% of the cases. Furthermore, we present different possible methodologies to overcome the database selection issue.