Apart from its tremendous enhanced transfer performances, the LTE/EPC mobile network is intended to distinguish itself from previous mobile technologies as an all-IP system. Nevertheless, far from usual IP QoS management policies, its QoS model inherits many characteristics of circuit oriented model of legacy standards. Additional signalling procedures are required in order to establish an end-to-end dedicated bearer for each desired QoS level. A major issue of this QoS model is the management load related to contexts and bearers established by each user equipment. This paper proposes an analytical model to evaluate the impact of this standard QoS model in terms of Context Load, Processing Load and Memory Access Rate in various LTE/EPC network elements. Simulation results are then presented to evaluate the impact of different realistic scenarios of QoS deployment.