  We study how the graph structure of the Internet at the Autonomous Systems
(AS) level evolved during a decade. For each year of the period 2008-2017 we
consider a snapshot of the AS graph and examine how many features related to
structure, connectivity and centrality changed over time. The analysis of these
metrics provides topological and data traffic information and allows to clarify
some assumptions about the models concerning the evolution of the Internet
graph structure. We find that the size of the Internet roughly doubled. The
overall trend of the average connectivity is an increase over time, while that
of the shortest path length is a decrease over time. The internal core of the
Internet is composed of a small fraction of big AS and is more stable and
connected that external cores. A hierarchical organization emerges where a
small fraction of big hubs are connected to many regions with high internal
cohesiveness, poorly connected among them and containing AS with low and medium
number of links. Centrality measurements indicate that the average number of
shortest paths crossing an AS or containing a link between two of them
decreased over time.
