Sensitivity formulas of performance in two-server cyclic queueing networks with phase-type distributed service times

With the approach of the infinitesimal generator perturbation, sensitivities of the steady-state performance are studied in two-server cyclic queueing networks with phase-type distributed service times. Sensitivity formulas expressed by the potentials of the networks are given for parameter-dependent performance functions. An algorithm to compute the potentials and the performance derivatives of the networks is given, and a numerical example is provided.