A new QOS-guaranteed cell discarding strategy: self-calibrating pushout

In order to fully utilize network resources while still providing satisfactory quality of service (QOS) to all network users, it becomes necessary to prioritize users' traffic according to their service requirements. A queue manager located at each output port of an ATM (asynchronous transfer mode) switch will be responsible for selectively discarding cells and transmitting cells based on their priority levels so that each service class's QOS requirement is guaranteed. The queue manager employs a new cell discarding scheme, called self-calibrating pushout (SCP), to balance the cell loss rates of the low and high loss priorities in real time such that each priority's cell loss rate requirement is met. The queue manager also adopts a cell scheduling scheme, called earliest-due-date (EDD). It time-stamps each arriving cell with a value equal to the sum of the arrival time and the maximum allowable queueing delay and then transmits cells with the smaller time stamp values. The performance of the queue manager (cell loss rates and cell delays) has been studied through computer simulations and the results are quite satisfactory.