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www.caida.org > publications : papers : 2012 : revealing_mpls_tunnels
Revealing MPLS tunnels obscured from traceroute
B. Donnet, M. Luckie, P. Mérindol, and J. Pansiot, "Revealing MPLS tunnels obscured from traceroute", ACM SIGCOMM Computer Communication Review (CCR), vol. 42, no. 2, pp. 87--93, Apr 2012.
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Revealing MPLS tunnels obscured from traceroute

Benoit Donnet 2
Matthew Luckie 1
Pascal Mérindol 3
Jean-Jacques Pansiot 3
1

CAIDA, San Diego Supercomputer Center, University of California San Diego

2

Université de Liège, Liège, Belgium

3

Université de Strasbourg, Strasbourg, France

Operators have deployed Multiprotocol Label Switching (MPLS) in the Internet for over a decade. However, its impact on Internet topology measurements is not well known, and it is possible for some MPLS configurations to lead to false router-level links in maps derived from traceroute data. In this paper, we introduce a measurement-based classification of MPLS tunnels, identifying tunnels where IP hops are revealed but not explicitly tagged as label switching routers, as well as tunnels that obscure the underlying path. Using a large-scale dataset we collected, we show that paths frequently cross MPLS tunnels in today‛s Internet: in our data, at least 30% of the paths we tested traverse an MPLS tunnel. We also propose and evaluate several methods to reveal MPLS tunnels that are not explicitly flagged as such: we discover that their fraction is significant (up to half the explicit tunnel quantity) but most of them do not obscure IP-level topology discovery.

Keywords: measurement methodology, topology
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