Assessment of QoS adaptation and cyber-defense mechanisms in networked systems

The paper describes methods to evaluate the QoS capability of a networked system S operating under hostile environment conditions. We evaluate the run-time compliance of system S with the QoS prescription of applications in terms of non-functional attributes that capture the QoS behavior of S (e.g., transaction latency & drop rate in an on-line web service). We benchmark the QoS capability of S by exercising stress-tests on a simulation model of S with artificially injected environment conditions. Our model-based system assessment methods are anchored on PO-MDP frameworks that are currently advocated for network reliability and performance analysis. As case study, we describe the assessment of a CDN (content distribution network) vis-a-vis the content read latency and overhead experienced by clients. Our CDN assessment employs models of the internal algorithmic processes that strive to optimally place the content caching nodes in a distribution topology.