tood, and design measures that can be put in place to evolve the aspects of the network that are under stress to maintain the expected level of service. CHAPTER 5 NETWORK ROADMAP EVOLUTION A Generic Template We suggest a sequence of steps to manage reactive evolution of a network. You can start by tabulating the expected levels of service, including critical attributes that could categorize the service. The KPIs of the network need to be listed, along with the service expectation to complete the understanding of requirements of network resilience. You can also mark critical KPIs among those that would necessarily need to be addressed. Next the challenges that can be imposed on the network should be tabulated, including detailed explanations about the impact on the network, by positing impacts on the KPI and the variations that could be expected. The intent of such tabulation is to gain a critical understanding of the challenge to the network and to understand the detailed impacts on the characteristics of the network as denoted by the KPIs. It is also recommended to include past challenges that have been recorded during the operations of the network under question and how the critical KPIs were impacted during these. The next step would be to link the critically impacted KPIs and make an assessment of the parts of the system that are unable to maintain the requisite functionality and thus impair the KPI as a service of the network. The critical components of the system should then be analyzed to understand how these can be reactively managed to address the challenge posed and to ensure that the key services offered by the network still manage to satisfy QoS criteria set on the operations. To complete the process, the reactive changes that are necessary are then encoded as a set of steps to be triggered manually or are recommended to be built into a set of automated processes in the network that could reactively address the challenge by managing and evolving the necessary parts of the network to satisfy the operat