Real-time adaptive bandwidth allocation for ATM switches

In order to meet the ATM Forum recommendations, rates must be guaranteed to each individual ATM connections across a high-speed switch fabric in the face of thousands of individual connections, burstiness of traffic in individual connections, a wide diversity of rates, differing expectations of rates for different traffic classes, and the arrival and departure of hundreds of connections per second. In addition, the situation is compounded by the presence of multicast traffic which has rate guarantees. We describe an architecture and Implementation for an ATM switching system which address the above requirements. Our approach uses a novel two-level scheduling algorithm: a higher level scheduling algorithm for aggregated cell units called frames and a distribution scheme for cells within a frame. This approach has significant advantages in terms of implementation complexity. It is particularly effective in treating traffic with differing QoS requirements differently in the process of flow control across the switching fabric. It enables the fulfilment of arbitrary rate guarantees to individual connections in an easily controllable way. It makes the scheduling of multicast particularly efficient and easy. We describe all these advantages and present numerical results supporting our claims. Implementational features of the architecture are discussed to demonstrate the feasibility of such a design