<div>Originally, networks were engineered to provide only one type of service, i.e. either voice or data, so only one level of resiliency was requested. This trend has changed, and today’s approach in service provisioning is quite different. A Service Level Agreement (SLA) stipulated between users and service providers (or network operators) regulates a series of specific requirements, e.g., connection set-up times and connection availability that has to be met in order to avoid monetary fines. In recent years this has caused a paradigm shift on how to provision these services. From a “one-solution-fits-all” scenario, we witness now a more diversified set of approaches where trade-offs among different network parameters (e.g., level of protection vs. cost and/or level of protection vs. blocking probability) play an important role.</div><div>This chapter aims at presenting a series of network resilient methods that are specifically tailored for a dynamic provisioning with such differentiated requirements. Both optical backbone and access networks are considered. In the chapter a number of provisioning scenarios - each one focusing on a specific Quality of Service (QoS) parameter - are considered. First the effect of delay tolerance, defined as the amount of time a connection request can wait before being set up, on blocking probability is investigated when Shared Path Protection is required. Then the problem of how to assign “just-enough” resources to meet each connection availability requirement is described, and a possible solution via a Shared Path Protection Scheme with Differentiated Reliability is presented. Finally a possible trade off between deployment cost and level of reliability performance in Passive Optical Networks (PONs) is investigated. The presented results highlight the importance of carefully considering each connection’s QoS parameters while devising a resilient provisioning strategy. By doing so the benefits in terms of cost saving and blocking probability improvement becomes relevant, allowing network operators and service providers to maintain satisfied customers at reasonable capital and operational expenditure levels</div>
An efficient hybrid protection scheme with shared/dedicated backup paths on elastic optical networks
