Calypso reveals the physical infrastructure behind global Internet paths by enabling traceroute-to-submarine cable mappings from tracroutes. Calypso integrates network infrastructure maps, rights-of-use knowledge, and speed-of-light constraints to reveal hidden submarine cable dependencies and criticalities. Use Calypso to assess resilience, compare regional exposure, and quantify cable importance with Route Stress.
Read the paperhere ↗, or interact with the globe on the right to visualize traceroute mappings by Calypso between any two cities.
Hidden Highways of the Internet
Submarine cables form the physical backbone of the global Internet. Stretching across ocean floors and linking continents through coastal landing points, they carry nearly all international data traffic. Though largely invisible to end users, these systems underpin economic activity, cloud infrastructure, research networks, and national security communications worldwide.
0%
of international traffic
0+
active cables as of 2026
0+ km
of subsea fiber deployed
Despite their scale, submarine cables concentrate enormous volumes of traffic into a limited number of routes and landing regions. Failures caused by natural disasters, anchoring incidents, infrastructure damage, or geopolitical conflict can disrupt connectivity across entire regions within hours. The global Internet depends on infrastructure that is both critical and exposed.
The Submarine Cable Network is Fragile ...
Major cable cuts in recent years have disrupted traffic across Africa, Asia, and the Middle East, causing latency spikes, packet loss, and prolonged outages. Repairs can take weeks and cost millions. Yet operators and policymakers often lack visibility into which cables carry specific traffic flows, making it difficult to assess true exposure, benchmark resilience, or prioritize protection efforts.
Ghana Regulator Update on Cable Breaks
National Communications Authority (Ghana) · Mar 2024
Read report ↗
... hard to repair ...
Submarine cable failures are not rare events. Each year, hundreds of faults occur worldwide, caused by fishing activity, anchoring, natural disasters, and infrastructure damage. With a limited global fleet of specialized repair vessels, restoration is slow, expensive, and logistically complex. Even a single break can disrupt connectivity across multiple countries for weeks.
~$0 million
dollars to repair
up to 0
weeks of repair time
~0
cable repair ships worldwide
... and extremely Opaque
Despite their critical role, submarine cables operate with limited public visibility. Ownership is often shared across consortia, capacity is leased through long-term rights-of-use agreements, and routing technologies obscure the physical paths traffic actually takes. Operators may understand their own infrastructure, but cross-network dependencies remain difficult to observe. Without cable-level visibility, assessing real exposure and resilience is inherently challenging.
Calypso brings measurement-based visibility to this hidden infrastructure.
How Calypso works
Step 1: Modeling network infrastructure
Calypso's Chartbook is a unified model of physical Internet connectivity built from three infrastructure layers:
- Submarine cables: Calypso obtains the latest submarine cable/landing point geometries from TeleGeography. It then applies cable unfolding to convert multi-landing systems into segment-level links between landing-point pairs , which enables Calypso to model connectivity at the segment-level.
- Terrestrial cables: To connect landing points with inland connectivity hubs (e.g., Ashburn, Chicago), and to model connectivity between landing points, Calypso uses terrestrial fiber paths inferred by iGDB, which showed that long-haul terrestrial routes typically align with existing rights-of-way such as highways and railroads, enabling Calypso's inland-to-coastal path modeling.
- Network rights-of-use: Calypso curates submarine cable rights-of-use from TeleGeography's Transport Network Research Service, allowing each cable segment to be checked for AS-level usage rights.
The result is a geography-aware, ownership-aware graph that constrains later inference to routes that are physically possible and policy-consistent.
Our Findings
We illustrate the value of Calypso by using Route Stress — a metric of the relative importance of submarine cables — to analyze two recent cable failures in South Africa, highlighting its utility in assessing the effects of disruptions on network performance.
Same events, different outcomes...
On Feb. 24, 2024, multiple submarine cables in the Red Sea were severed, affecting disrupting key data routes along the eastern coast of Africa. Three weeks later, on Mar. 14, 2024, a subsea landslide near the coast of Côte d'Ivoire damaged several major west African cable systems, causing widespread connectivity outages across the region.
South Africa, with submarine cable landings on both its east and west coasts, provides a natural case study. We compare its experience to that of Kenya to demonstrate Calypso’s ability to quantify the relative importance of submarine cables using Route Stress .
In the Route Stress panel, we present the top cables Calypso identified from a traceroute corpus collected at vantage points in South Africa.
On South Africa’s west coast, ACE, WACS, and SAT-3/WASC ranked higher in relative importance than EIG, one of the cables affected in this incident. Accordingly, network measurement signals (latency, jitter, and packet loss) show minimal disruption in South Africa, while the same signals in Kenya exhibit clear degradation.
Route Stress (ZA)
Route Stress estimates cable dependence as the share of mapped submarine-cable routes that traverse each system.
Failure Impact and Affected Cables
Region: near the Bab el-Mandeb Strait
Cables:
South Africa
Latency
Latency region annotation is shown from failure start (2024-02-24) through 2024-02-24. Left and right in-chart notes explain the behavior in that window.
Jitter
Jitter region annotation is shown from failure start (2024-02-24) through 2024-02-24. Left and right in-chart notes explain the behavior in that window.
Packet Loss
Packet Loss region annotation is shown from failure start (2024-02-24) through 2024-02-24. Left and right in-chart notes explain the behavior in that window.
Kenya
Latency
Latency region annotation is shown from failure start (2024-02-24) through 2024-02-24. Left and right in-chart notes explain the behavior in that window.
Jitter
Jitter region annotation is shown from failure start (2024-02-24) through 2024-02-24. Left and right in-chart notes explain the behavior in that window.
Packet Loss
Packet Loss region annotation is shown from failure start (2024-02-24) through 2024-02-24. Left and right in-chart notes explain the behavior in that window.
Frequently asked questions
About Us
Calypso is developed and maintained by Caleb Wang ↗ from Aqualab ↗ led by Prof. Fabian E. Bustamante ↗ at Northwestern University ↗.
We are extremely grateful to our collaborator Prof. Ramakrishnan Durairajan ↗, and Romain Fontugne ↗ for the invaluable discussions during earlier versions of this work.
We additionally thank IPinfo ↗and TeleGeography ↗ for providing critical data for us to develop Calypso.
This work is supported by the NSF.
