The Graph Structure of the Internet at the Autonomous Systems Level during Ten Years

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 weconsider a snapshot of the AS graph and examine how many features related tostructure, connectivity and centrality changed over time. The analysis of thesemetrics provides topological and data traffic information and allows to clarifysome assumptions about the models concerning the evolution of the Internetgraph structure. We find that the size of the Internet roughly doubled. Theoverall trend of the average connectivity is an increase over time, while thatof the shortest path length is a decrease over time. The internal core of theInternet is composed of a small fraction of big AS and is more stable andconnected that external cores. A hierarchical organization emerges where asmall fraction of big hubs are connected to many regions with high internalcohesiveness, poorly connected among them and containing AS with low and mediumnumber of links. Centrality measurements indicate that the average number ofshortest paths crossing an AS or containing a link between two of themdecreased over time.