!"#$ %&'$(' )* +, -.'# /(!.'0)( 1.23$4 56 7)2'0(8-)90:0$3;0&0( <.)= >$(8 ?.(8Abstract— Border Gateway Protocol (BGP) is an interdomainrouting protocol that allows Autonomous Systems (ASes) toapply local policies for selecting routes and propagating routinginformation. These routing policies are typically constrained bythe contractual commercial agreements between administrativedomains. For example, an AS sets its routing policy so that itdoes not provide transit services between two of its providers. Asa result, a route in the Internet may take a longer AS path thanthe shortest AS path. In this paper, we systematically analyzeAS paths and quantify the extent that routing policies in flate ASpaths in the Internet. Our results show that AS path inflation inthe Internet are more prevalent than expected. We first presentthe extent of AS path inflation observed from the Route Viewrouting tables. We find that from an ISP, at least 67% of ASpaths are inflated by at least one AS hop and AS paths can beinflated by as long as 5 AS hops. We then employ two typicalrouting policies to show the extent of AS path inflation for allAS pairs. We find that at least 45% of AS paths are inflated byat least one AS hop and AS paths can be in fl ated by as long as9 AS hops given a typical routing policy model. 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