Time as a Metric for Defence in Survivable Networks

Critical infrastructures of today’s society are built over networks that require a degree of survivability not foreseen when they were built. This paper reports on work in progress in a European project that aims to safeguard critical infrastructures such as electricity and telecom networks. It assumes that there will be accidents, attacks, and failures in parts of a network. The goal of safeguard is to enable delivery of the essential services despite these. Hence, we define a metric for network level survivability in terms of a continuous function of critical components’ availability and integrity. We further go on to measure the survivability of the system in terms of the time taken to breach of survivability. In a system where the implemented defence/recovery mechanisms are not adequate, this time is finite. In a system that implements self-healing, the presence of attacks and failures is continuously compensated by defence and recovery mechanisms. Again, a measure of time to recover from component failures is a key to increased network survivability. The paper presents a preliminary study of defence mechanisms in a telecom management network, and illustrates how simulations of the network and harmful data can be used to identify trade-offs that are central to increased survivability. Keywords—Survivability, Simulation, Intrusion Tolerance, Dependability, Timely defence.