  Internet eXchange Points (IXPs) are core components of the Internet
infrastructure where Internet Service Providers (ISPs) meet and exchange
traffic. During the last few years, the number and size of IXPs have increased
rapidly, driving the flattening and shortening of Internet paths. However,
understanding the present status of the IXP ecosystem and its potential role in
shaping the future Internet requires rigorous data about IXPs, their presence,
status, participants, etc. In this work, we do the first cross-comparison of
three well-known publicly available IXP databases, namely of PeeringDB,
Euro-IX, and PCH. A key challenge we address is linking IXP identifiers across
databases maintained by different organizations. We find different AS-centric
versus IXP-centric views provided by the databases as a result of their data
collection approaches. In addition, we highlight differences and similarities
w.r.t. IXP participants, geographical coverage, and co-location facilities. As
a side-product of our linkage heuristics, we make publicly available the union
of the three databases, which includes 40.2 % more IXPs and 66.3 % more IXP
participants than the commonly-used PeeringDB. We also publish our analysis
code to foster reproducibility of our experiments and shed preliminary insights
into the accuracy of the union dataset.
