The extent of AS path inflation by routing policies

A route in the Internet may take a longer AS (autonomous systems) path than the shortest AS path due to routing policies. We systematically analyze AS paths and quantify the extent to which routing policies inflate AS paths. The results show that AS path inflation in the Internet is more prevalent than expected. We first present the extent of AS path inflation observed from the route view routing tables. From an ISP, at least 55% of AS paths are inflated by at least one AS hop and AS paths can be inflated by as long as 6 AS hops. We then employ two typical routing policies to show the extent of AS path inflation for all AS pairs; we find that at least 45% of AS paths are inflated by at least one AS hop and AS paths can be inflated by as many as 9 AS hops. Quantifying AS path inflation in the Internet has important implications on the extent of routing policies and traffic engineering performed on the Internet, and on BGP (border gateway protocol) convergence speed.