Strength and weakness in diversity

The malfunction of one or more electronic communications junctions, or nodes, generally has little impact on the Internet as a whole. The global network’s redundancy and diversity help it survive such problems, making it robust and reliable despite its complexity and enormous size. Cyberterrorist attacks aimed at the most highly connected nodes, however, can break up the network into isolated parts, says a team of physicists.

The combination of error tolerance and vulnerability to attack is a generic property of communication networks, contend Albert-László Barabási and his coworkers at the University of Notre Dame in Indiana, in the July 27 Nature.

These networks have a characteristic structure. Whereas the vast majority of nodes have just a handful of links to other nodes, a few of the network’s nodes are more highly interconnected (SN: 9/25/99, p. 203). Accidental local failures rarely hamper a network’s global information-carrying ability, but the more highly interconnected nodes are much more important in network behavior. A troublemaker who knows how the system is connected could cause a lot of damage, Barabási suggests.

The same knowledge can do good, as well. “This work represents a notable first step towards understanding the robustness of the Internet,” comments Yuhai Tu of the IBM Thomas J. Watson Research Center in Yorktown Heights, N.Y. It provides “a useful framework for qualitatively describing and analyzing network performance.”

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