Telecom customers may have specific time periods during which they require extra resilience. However, these time-differentiated resilience requirements are not effectively addressed by current service level agreement (SLA) frameworks. To satisfy these high priority periods, a generic SLA framework typically provides upgraded protection over the entire service duration, which is unnecessary and expensive. In this study, we propose a novel SLA framework that allows customers to specify critical windows (CWs) to address their time-differentiated demands for resilience. CWs correspond to the resilience-sensitive periods, and connections are backed up during CWs using pre-cross-connected protection. To achieve high resource efficiency, we identify opportunities for backup resource sharing in a time-domain multiplexing manner. Two heuristic schemes are proposed, namely, Locally and Globally CW-Aware connection assignments. Our study on a sample optical mesh network shows that, by applying our SLA framework, 1) resource efficiency can be significantly improved, 2) CWs are effectively protected with high resilience (in terms of availability), 3) the availability of CWs can be increased almost linearly with used backup resources, and (4) our framework (approach) requires low operational complexity.
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