In a previous work, we have proposed the PD (Proportional and Derivative) algorithm, which is an explicit algorithm for ABR flow control in ATM networks. The performance study of this algorithm has shown that on one hand, it achieves a full utilization of network links and the fairness in bandwidth allocation. On the other hand, the PD algorithm ensures good buffer occupancy with respect to the fixed threshold. In this study, both a simple network topology and the GFC1 topology have been considered. The PD algorithm implies control gains in the calculation of the Supported rate, thus in this paper, we are interested in investigating the effect of the control gain choice on the stability of the system, in terms of buffer occupancy and source rate behavior, when the PD algorithm is applied.