s for network roadmap evolution, which we will discuss in detail in the next chapter. Planned Evolution This section will discuss techniques of testing the resilience of the network and what the results of the testing can tell us about the network. This would expose the gaps in the roadmap and help you take steps to evolve the roadmap to address those gaps in a planned manner. Also we will explain how reactive evolution can result from sudden changes and how changes can be anticipated. Network Resilience What is meant by resilience? What does it take for an entity to be resilient? re-sil-ience The ability to recover quickly from illness, change, or misfortune; buoyancy. The American Heritage Dictionary of the English Language, Fourth Edition Resilience is denoted by the ability to be able to recover quickly from events or external forces that may cause disruption. A similar description is very much applicable to network resilience. Just as different things are innately perceived to have varying abilities of resilience, experts have found that networks too need to be designed and built to be resilient. In an age where all networks are interconnected and most systems run out of the network, the system is as strong as its weakest link, which in this case could be any part of the network that is prone to attacks or disruptions, both natural and manmade. Failures and faults that could cripple the network or add to downtime are most certainly going to cause huge losses to different entities in following ways: Loss of revenue to the business due to failures in network and penalty clauses about availability Loss of trust in the quality of the network's ability to survive failures and thwart future attacks Disruption of operations and services to operators running businesses out of the network Disruptions to customers and end users who may be running real-time and life critical operations from services provided by the network With the increasing number of services and applications being hosted on the Cloud, disruptions to