Internet paths often overlap physically despite logical separation
Disjoint in Name Only: Illusory Resilience in the Internet
Networking and Internet Architecture
Summary
Internet connections that seem separate on paper often share the same physical cables or routes, making them less reliable than they appear. The authors developed a way to measure this hidden overlap, called the Illusory Resilience Index, using public data about network disruptions and physical infrastructure. They found many cases where paths thought to be independent actually face common risks, especially within the same region or cable corridor. This work helps identify when networks need better verification to ensure true diversity and reliability.
What this means in practice
- •For network operators: Identify hidden shared risks in supposedly independent Internet paths to improve physical path verification and resilience planning.
- •For infrastructure planners: Use public network and hazard data to avoid colocating network assets that seem diverse logically but share physical vulnerabilities.
Authors
Subhadeep Sahoo, Hrishikesh B Acharya
Abstract
Internet path diversity is usually verified at the logical layer: two alternatives may share no AS or IP link yet traverse the same facility, conduit, or submarine landing zone. We call this gap illusory resilience and define the Illusory Resilience Index (IRI) as the latent hazard-weighted physical overlap of a logically disjoint path pair. To detect such hidden exposure without carrier underlay maps, we audit three public signals: correlated BGP withdrawals during documented physical incidents, operator interconnection-footprint overlap, and shared submarine landing zones. Two signals survive calibration; the 60-second BGP signal does not. Across 47 operators in ten regions, same-region pairs have substantially greater listed facility overlap than cross-region pairs, and one Marseille campus colocates 153 operator pairs. Across 68 cable systems in twelve corridors, 31-100% of candidate within-corridor pairs share a 25 km coastal hazard zone; two corridors are fully saturated, and the same rule recovers ten of eleven cable pairs documented as co-damaged in 2024. The rejected temporal predicate has a 0.444 null firing rate and no hits among twelve monitored positive pairs. Public data therefore expose substantial shared-risk structure behind nominal diversity and identify where stronger physical-path verification is warranted.