On the prevalence and characteristics of MPLS deployments in the open internet

  • Authors:
  • Joel Sommers;Paul Barford;Brian Eriksson

  • Affiliations:
  • Colgate University, Hamilton, NY, USA;University of Wisconsin-Madison, Madison, WI, USA;Boston University, Boston, MA, USA

  • Venue:
  • Proceedings of the 2011 ACM SIGCOMM conference on Internet measurement conference
  • Year:
  • 2011

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Abstract

Multi-Protocol Label Switching (MPLS) is a mechanism that enables service providers to specify virtual paths through IP networks. The use of MPLS in the open Internet (i.e., public end-to-end paths) has important implications for users and network neutrality since MPLS is frequently used in traffic engineering applications today. In this paper we present a longitudinal study of the prevalence and characteristics of MPLS deployments in the open Internet. We use path measurement data collected over the past 3.5 years by the CAIDA Archipelago project (Ark), which consist of over 10 billion individual traceroutes between hosts throughout the Internet. We use two different techniques for identifying MPLS paths in Ark data: direct observation via ICMP extensions that include MPLS label information, and inference using a Bayesian data fusion methodology. Our direct observation method can only identify uniform-mode tunnels, which very likely underestimates MPLS deployments. Nonetheless, our results show that the total number of tunnels observed in a given measurement period has varied widely over time with the largest deployments in tier-1 providers. About 7% of all autonomous systems deploy MPLS and this level of deployment has been consistent over the past three years. The average length of an MPLS tunnel has decreased from 4 hops in 2008 to 3 hops in 2011, and the path length distribution is heavily skewed. About 25% of all paths in 2011 cross at least one MPLS tunnel, while 4% cross more than one. Finally, data observed in MPLS headers suggest that many ASes employ some types of traffic classification and engineering in their tunnels.