Robustness analysis is the process of checking whether a system's function is maintained despite perturbations. Robustness analysis of biological models is typically applied to differential equation models of biochemical reaction networks. While robustness is primarily a yes-or-no question, for many applications in biological models, it is also desired to compute a quantitative robustness measure. Such a measure is usually defined to be the maximum size of perturbations that the system can still tolerate. In addition, it is often of interest to specifically compute fragile perturbations, i.e., perturbations for which the system loses its function.