  Submarine cables constitute the backbone of the Internet. However, these
critical infrastructure components are vulnerable to several natural and
man-made threats, and during failures, are difficult to repair in their remote
oceanic environments. In spite of their crucial role, we have a limited
understanding of the impact of submarine cable failures on global connectivity,
particularly on the higher layers of the Internet.
  In this paper, we present Nautilus, a framework for cross-layer cartography
of submarine cables and IP links. Using a corpus of public datasets and
Internet cartographic techniques, Nautilus identifies IP links that are likely
traversing submarine cables and maps them to one or more potential cables.
Nautilus also gives each IP to cable assignment a prediction score that
reflects the confidence in the mapping. Nautilus generates a mapping for 3.05
million and 1.43 million IPv4 and IPv6 links respectively, covering 91% of all
active cables. In the absence of ground truth data, we validate Nautilus
mapping using three techniques: analyzing past cable failures, using targeted
traceroute measurements, and comparing with public network maps of two
operators.
