Infer the list of Tier 1 ASes by computing the largest clique (complete graph) in the AS topology graph. To compute the largest clique follow this simple greedy heuristic. Rank all the ASes according to their degree and place them to set R = {AS1, AS2, ...}, where degree(ASi) > degree(ASi+1). Initialize the clique S = {AS1}. If AS2 is connected to AS1, add it to S. That is S = {AS1, AS2}, If AS3 is connected to AS1 and AS2, add it to S. That is S = {AS1, AS2, AS3}. Terminate when you find the first AS that is not connected to all ASes in S. Table 1: Give the size of the T1 list and the first 10 ASes that were added to S. You can use the AS-to-organization mapping (http://www.caida.org/data/as-organizations/) to map AS numbers to the organizations that own them