On the geographical properties of BGP routing tables

Recently, M. Faloutsos et al. published an unexpected result: autonomous systems (AS) interconnectivity exhibits a power-law degree distribution (see Proc. ACM SIGCOMM´99, 1999). This result has led to the construction of scale-free network models to characterize Internet topologies. Most of these works use the tables published by Oregon Route Views (http://www.antc.uoregon.edu/route-views/), and frequently the distributions measured do not exactly follow a power-law. Our work is different from previous ones in the sense that we use routing tables from several geographical sites, the union of all of them having a broader vision of AS connectivity. Also, we compare BGP tables of different sizes of AS and make use of the CCDF (complementary cumulative density function) to fit the power-law better. This comparison is based on the AS degree of connectivity, clustering coefficient and path length. Our results show that the topology of the Internet at the AS level could be modeled both as a scale-free network and as a small-world network. We also show that the Barabasi-Albert model (Albert, R. and Barabasi, A.-L., Rev. Modern Phys., vol.74, p.47, 2002) does not fit very well for small and medium AS degrees.