Although the Internet is famously designed to withstand a nuclear attack, millions in East Asia were rudely awakened to the limits of the network’s resiliency when an earthquake hit off the coast of Taiwan this past December. The quake cut six of the main service lines to the region, isolating users from the outside world for days and causing service interruptions that lasted for over a month. In fact, the damage wasn’t fully repaired until just last week.

The Internet, at its physical layer, is no different than any other networked system, meaning it is subject to failure if there is not sufficient redundancy to route around a component that fails. Reliable systems like the Internet minimize the number of bottlenecks at which they are vulnerable, but no system can ever be 100 percent reliable.

Redundant undersea loops of fiber-optic cable connect East Asia to North America, which limits the bandwidth loss from any single line’s failure. However, at least nine of the loops of fiber-optic cables that connect Asian countries to each other and to the outside world run through the Bashi Channel in the Luzon Strait—an area known for seismic activity, deep waters, strong currents, and powerful winds. On December 27, an earthquake damaged the lines and choked off the data streams to a large portion of the region.

While the earthquake severely damaged the region’s connection to the outside world, the Internet’s inherent characteristics helped to limit the impact. The Internet is a scale-free network, meaning that its characteristics do not change based on its size, and its built-in protocol allows information to take any available route within the network. This meant that data could still flow freely within the region, and that traffic could be rerouted to avoid the damaged area.

The countries with single or few connection points to the outside world could easily find themselves disconnected by a deliberate incident.

Still, so much of the region’s bandwidth flows through the Luzon Strait that the other available routes were choked with the redirected traffic. The overland cables from India and Russia could not handle the increase in traffic, and the capacity of satellites to transmit data proved lacking. Although some providers were back up and running within days, service interruptions persisted in East Asia for over a month.

This is not the first time a chokepoint in the Internet has failed, leaving a vast region isolated from the rest of the world. Pakistan faced a similar problem in June 2005, when the country's sole fiber-optic cable link to the outside world failed for 11 days, virtually cutting off all data feeds to the country. Similar vulnerabilities exist in many South American and African countries, where a single undersea cable connects an entire nation to the Internet outside its borders. Island states such as Iceland are also served by a single loop of fiber-optic cable, and are rarely connected at more than one physical point to the outside network. Nearly all of the fiber-optic cables that run west out of East Asia and Australia run through the Malacca Strait, an area of particular concern because of its frequent pirate attacks.

Geopolitical problems could also arise in the event of a physical network failure. China, for example, is heavily reliant on fiber-optic cables that run just off the coast of an island it considers a “rogue” territory. The countries with single or few connection points to the outside world could easily find themselves disconnected by a deliberate incident.

The network’s physical vulnerability raises economic concerns for its users that go beyond the business interests of network operators themselves. The business case for creating more redundant links is ambiguous: several Asian telecom companies said they would not invest more in backup lines to prevent another outage, citing the low possibility of a repeat incident, but another group of firms thinks differently. Three Chinese companies, New York-based Verizon, and two South Korean firms partnered to lay a fiber-optic loop connecting China and South Korea to the United States weeks before the earthquake, but following the outages the companies decided to construct the project as a robust "mesh" network system, rather than a single loop. And last month Asia Netcom announced plans to add a trans-Pacific loop to its undersea network, using a path that would avoid most of the region’s chokepoints. These firms have recognized that if and when a disruption occurs, their networks may be all the more valuable.

It may be the financial markets, another self-correcting system, that end up making the Internet more reliable. The earthquake shifted the financial analysis for some telecom companies, making unique cable routes more valuable. By the end of the year there may be sufficient redundancy in the undersea East Asia telecom network to avoid another outage like December’s.

This article is adapted from a report the author drafted for The Power and Interest News Report, where he is a Senior Analyst.