To construct a hierarchical tree of AS's we needed to find the best assignment of small clusters (AS's with small out-degree) to larger clusters. For this study, we extracted ``best path'' data from a routing table acquired from Oregon Route-views [29] dynamically on Feb. 20, 2001. BGP routers typically receive multiple paths to the same destination. The BGP best path algorithm decides which is the best path to install in the IP routing table and to use for forwarding traffic. These paths tend to use a highest-throughput lowest-latency link. Our algorithm has no other means to discover that information directly.