Evolution of the Internet AS-level ecosystem S. Shakkottai, M. Fomenkov, R. Koga, D. Krioukov and K. C. Claffy Eur. Phys. J. B, 74 2 (2010) 271-278 Published online: 16 February 2010 DOI: 10.1140/epjb/e2010-00057-x