Effects of node protections against intentional attack in complex communication networks

It is well-known that many complex communication networks, with their power-law nodal degree distribution, may be highly tolerant against random failures yet fragile under intentional attack which takes down network nodes in a decreasing order of their degrees. Different from existing studies on network robustness, we investigate the effects of a few different protection schemes which protect a limited set of high or medium-degree nodes from being crashed. We argue that such protections may have been widely implemented in communication systems. We show that though different schemes have different effects, overall speaking protecting a small fraction of high-degree nodes or even medium-degree ones significantly enhances network robustness. The results are supported by theoretical analyses and numerical simulations. Such studies provide some useful insights for improving network protection.