Picture the communications network as a series of nodes: If there is just one connection between two nodes and it is destroyed in a nuclear attack, it is no longer possible to communicate. Now imagine nodes with multiple connections to other nodes, providing an alternate path of communication if some nodes are taken out. The question for Baran was, how much redundancy is enough? Through simulations of an attack, Baran and his colleagues found that if you have three levels of redundancy, the probability that two nodes in the network could survive a nuclear attack was extremely high.
