Defending Networks Against Cascading Failure

Just as foresters can often halt a forest fire from burning out of control by deliberately setting firebreaks, it might be possible to reduce the size or spread of outages in a network in the wake of an attack or overload. The Internet and the electrical grid are just two such networks that might benefit from a new model devised by Adilson Motter of the Max Planck Institute for the Physics of Complex Systems in Dresden. Several previous network models have shown how an attack on key nodes of a system can cascade into a catastrophic failure. Motter's model shows how such a failure can be mitigated by shutting down selected peripheral nodes that handle only small amounts of the network's total load. Simulating attacks on networks showed that answering the original attack with several successive rounds of precautionary node shut-down drastically reduced the size of the overall cascade. (Physical Review Letters; motter@mpipks-dresden.mpg.de)