Scalable and Accurate Identification of AS-level Forwarding Paths
Authors:	Z. M. Mao D. Johnson J. Rexford J. Wang R. H. Katz
Published:	Proceedings of INFOCOM, 2004
URL:	http://www.ieee-infocom.org/2004/Papers/34_2.PDF http://www.eecs.umich.edu/~zmao/Papers/infocom04.pdf
Entry Date:	2004-06-30
Abstract:	Traceroute is used heavily by network operators and researchers to identify the IP forwarding path from a source to a destination. In practice, knowing the Autonomous System (AS) associated with each hop in the path is also quite valuable. In previous work we showed that the IP-to-AS mapping extracted from BGP routing tables is not sufficient for determining the AS- level forwarding paths [1]. By comparing BGP and traceroute AS paths from multiple vantage points, [1] proposed heuristics that identify the root causes of the mismatches and fix the inaccurate IP-to-AS mappings. These heuristics, though effective, are labor- intensive and mostly ad hoc. This paper proposes a systematic way to construct accurate IP-to-AS mappings using dynamic programming and iterative improvement. Our algorithm reduces the initial mismatch ratio of 15% between BGP and traceroute AS paths to 5% while changing only 2.9% of the assignments in the initial IP-to-AS mappings. This is in contrast to the results of [1], where 10% of the assignments were modified and the mismatch ratio was only reduced to 9%. We show that our algorithm is robust and can yield near-optimal results even when the initial mapping is corrupted or when the number of probing sources or destinations is reduced. Our work is a key step towards building a scalable and accurate AS-level traceroute tool.
Datasets:	whois data was obtained from Internet Routing Registries (IRRs). Traceroute data sets were collected from 8 locations, done to 200,000 prefixes, 2 addresses in each prefix, between May and June, 2003. BGP routing table data was obtained around May 29, 2003 from RouteViews (from 23 ASes), RIPE-NCC (from 75 ASes), SingAREN
Results:	Mismatch ratio improved from 15% to 5% by changing only 2.9% of IP-to-AS mappings Results are almost as good when using only one probe for each unique BGP path at a given vantage point, even if that path corresponds to multiple prefixes (87% reduction in traceroute probes) or when using only four out of the eight vantage points.
References:	Continuation of work: Z. Morley Mao, Jennifer Rexford, Jia Wang, and Randy Katz, "Towards an Accurate AS-level Traceroute Tool," in Proc. ACM SIGCOMM, September, 2003.