Why Do Critical Infrastructures Cascade?

One of the unsolved problems of critical infrastructure protection is the "cascade failure" problem. The 2003 Blackout is an extreme example of how seemingly small failures in a remote part of a major national power grid can cause nearly 100% collapse of the entire system. Over 50 million people were without power. And yet, the electric power grid is considered stable and resilient. I analyze 3 abstract network models of cascade failure and speculate on how such failures might be avoided in critical infrastructures such as power grids, traffic congested highways, and computer networks. The MRS model is based on computer network resiliency, and suggests a prevention strategy based on careful placement of rollback points in the network. The epidemic model is based on network topology, and suggests a prevention strategy based on the network's spectral radius. Finally, my own Kirchhoff network model assumes a network that supports Kirchhoffs' Law of flow in a network, and leads to careful addition of one or more links in order to stabilize the vulnerable network. 

Ted Lewis is currently the Executive Director, Center for Homeland Defense and Security, and Professor of Computer Science at the Naval Postgraduate School, Monterey, CA. He is author of Critical Infrastructure Protection: Defending a Networked Nation, John Wiley & Sons, 2006, and Network Science: Theory and Applications, John Wiley & Sons, 2009.