Networks’ resilience


Stories from a connected world – Networks’ resilience

In July 2001, a train derailed [PDF] in a Maryland tunnel , causing a fire. The fire fused optical fibers in the tunnel and, after a short time, Internet traffic slowed down in part of the United States. It is uncommon that an accident reduces macroscopically the efficiency of the Internet. At any given time, thousands of routers are out of use. However, the network seems to tolerate smoothly this chronic malfunction.

This extraordinary resilience appears in many other systems structured as networks. Social groups such as companies or institutions always suffer communication problems. However, they manage to carry on complicated tasks such as building an airplane or collecting taxes. Many species become extinct by natural selection. However, the biosphere continues working. Genetic mutations are ordinary events. But organisms show tremendous strength, even when there are mutations that lead to the disappearance of a large number of proteins.

Several groups of researchers have performed computer simulations to see how many nodes of the Internet would have to  be removed to stop it working. Surprisingly, even after removing 80% of them, the network remains connected. To understand this result, researchers have undertaken the same experiment with an artificial network, in which the superconnected nodes of the Internet are missing. In this case, the network fragments much faster. The presence of superconnectors is the key to the high resilience of many networks.

Want to know more? Read “Networks. A Very Short Introduction

(Movie adapted from “Einstein a la platja”. Thanks to Barcelona Televisi√≥)

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