Survivability as a generalization of recovery

Social infrastructure systems such as communication, transportation, power and water supply systems are now facing various types of threats including component failures, security attacks and natural disasters, etc. Whenever such undesirable events occur, it is crucial to recover the system as quickly as possible because the downtime of social infrastructure causes catastrophic consequences in the society. In the business continuity context, Recovery Time Objective (RTO) has been used as a criterion to specify the allowable maximum time to recover from system failure events. While RTO gives the requirement for system recovery time, performance degradation of infrastructure service during the recovery period is another dimension that should be taken into consideration. In this paper, we introduce survivability as a generalization of recovery behavior which can address the performance impacts during the recovery and show a survivability quantification example in a escalating and deferred repair system.