Multiobjective Monitoring for SLA Compliance

Service level agreements (SLAs) define performance guarantees made by service providers, e.g., in terms of packet loss, delay, delay variation, and network availability. In this paper, we describe a new active measurement methodology to accurately monitor whether measured network path characteristics are in compliance with performance targets specified in SLAs. Specifically, we: 1) introduce a new methodology for measuring mean delay along a path that improves accuracy over existing methodologies, and a method for obtaining confidence intervals on quantiles of the empirical delay distribution without making any assumption about the true distribution of delay; 2) introduce a new methodology for measuring delay variation that is more robust than prior techniques; 3) describe a new methodology for estimating packet loss rate that significantly improves accuracy over existing approaches; and 4) extend existing work in network performance tomography to infer lower bounds on the quantiles of a distribution of performance measures along an unmeasured path given measurements from a subset of paths. Active measurements for these metrics are unified in a discrete time-based tool called SLAm. The unified probe stream from SLAm consumes lower overall bandwidth than if individual streams are used to measure path properties. We demonstrate the accuracy and convergence properties of SLAm in a controlled laboratory environment using a range of background traffic scenarios and in one- and two-hop settings, and examine its accuracy improvements over existing standard techniques.