Abstract This paper proposes an analytical method to evaluate the delay violation probability of traffic flows with statistical Quality-of-Service (QoS) guarantees in a Generalized Processor Sharing scheduler. The statistical QoS targets, for each service class, are expressed in terms of a delay threshold and delay violation probability. We study both the single node and the endto-end paths comprising multiple schedulers. Moreover, we assume that traffic admits a linear variance envelope, therefore, we account for Leaky-Bucket-regulated traffic, for general MarkovModulated Poisson Process sources and Markov-Modulated Fluid Process sources and, more in general, to the wide class of sources for which the variance of the cumulative generated traffic can be upper bounded by a linear function of time. Under these assumptions, we are able to derive an approximation on delay distributions for each class of the GPS scheduler. Moreover, by exploiting a novel framework for the calculation of st...