An implementation study of dual proportional-plus-derivative controller for explicit rate based ABR service

An explicit rate (ER) based congestion control scheme to support a class of best effort service known as available bit rate service (ABR) is being proposed by the ATM Forum. In this scheme, the network informs the sources from time to time, the maximum rate at which they can transmit. We present an all software based implementation of one variant of this control scheme. We apply principles of control theory and implement the ER scheme via a dual proportional-plus-derivative controller (DPDC). We have studied the transient performance of the control in the presence of high priority cross traffic. The experimental results have been obtained from an ATM testbed which consists of two ATM LANs, one located in Princeton (USA) and the other in Berlin (Germany), that are connected by a T1 link. The results show that the DPDC scheme is very stable with good transient response, even under extreme loading conditions and very long propagation delays.