Design and performance analysis of a 32×32 hybrid ATM switch architecture

Services offered within fibre-based asynchronous transfer mode (ATM) networks may range from circuit emulations, where extremely low cell loss rates are essential, to high-speed variable rate services where a degree of cell loss can be tolerated but whose bandwidth requirements may be extremely bursty and unpredictable. ATM switches deployed within these networks must be extremely robust to support such a broad spectrum of high speed services and must also be scalable to elegantly incorporate future applications without any performance degradation. The authors present a high performance self routing tree/banyan/knockout based 32×32 hybrid ATM switch that can support a wide range of services having diverse performance objectives and traffic characteristics. The proposed architecture achieves high performance by utilizing a 3 stage expansion network which is completely non-blocking. The philosophy behind this design is the knockout principle which has been shown to achieve cell loss probabilities of the order of 10^-6 with 8 buffers for each output regardless of the traffic load and the switch size. The expansion network is followed by a 2 stage banyan network which makes the switch partially blocking. The final stage is a fast output interface which is the only section of the switch which has to work at 8 times the link speed. The rest of the switch functions at link speed. The proposed switch, thus naturally lends itself to output queueing without any internal speedup