On AS-level path inference

  • Authors:
  • Z. Morley Mao;Lili Qiu;Jia Wang;Yin Zhang

  • Affiliations:
  • University of Michigan;University of Texas, Austin, TX;AT&T Labs - Research;University of Texas, Austin, TX

  • Venue:
  • SIGMETRICS '05 Proceedings of the 2005 ACM SIGMETRICS international conference on Measurement and modeling of computer systems
  • Year:
  • 2005

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The ability to discover the AS-level path between two end-points is valuable for network diagnosis, performance optimization, and reliability enhancement. Virtually all existing techniques and tools for path discovery require direct access to the source. However, the uncooperative nature of the Internet makes it difficult to get direct access to any remote end-point. Path inference becomes challenging when we have no access to the source or the destination. Moveover even when we have access to the source and know the forward path, it is nontrivial to infer the reverse path, since the Internet routing is often asymmetric.In this paper, we explore the feasibility of AS-level path inference without direct access to either end-points. We describe RouteScope-a tool for inferring AS-level paths by finding the shortest policy paths in an AS graph obtained from BGP tables collected from multiple vantage points. We identify two main factors that affect the path inference accuracy: the accuracy of AS relationship inference and the ability to determine the first AS hop. To address the issues, we propose two novel techniques: a new AS relation-ship inference algorithm, and a novel scheme to infer the first AS hop by exploiting the TTL information in IP packets. We evaluate the effectiveness of RouteScope using both BGP tables and the AS paths collected from public BGP gateways. Our results show that it achieves 70% - 88% accuracy in path inference.