  We present a statistical analysis of different metrics characterizing the
topological properties of Internet maps, collected at two different resolution
scales: the router and the autonomous system level. The metrics we consider
allow us to confirm the presence of scale-free signatures in several
statistical distributions, as well as to show in a quantitative way the
hierarchical nature of the Internet. Our findings are relevant for the
development of more accurate Internet topology generators, which should
include, along with the scale-free properties of the connectivity distribution,
the hierarchical signatures unveiled in the present work.
