No abstract

Abstract-This paper describes the architecture for a workconserving server using a combined I/O-buffered crossbar switch. The switch employs a novel algorithm based on output occupancy, the lowest occupancy output first algorithm (LOOFA), and a speedup of only two. A work-conserving switch provides the same throughput performance as an output-buffered switch. The workconserving property of the switch is independent of the switch size and input traffic pattern. We also present a suite of algorithms that can be used in combination with LOOFA. These algorithms determine the fairness and delay properties of the switch. We also describe a mechanism to provide delay bounds for real-time traffic using LOOFA. These delay bounds are achievable without requiring output-buffered switch emulation.

Abstract-This paper describes the architecture for a workconserving server using a combined I/O-buffered crossbar switch. The switch employs a novel algorithm based on output occupancy, the lowest occupancy output first algorithm (LOOFA), and a speedup of only two. A work-conserving switch provides the same throughput performance as an output-buffered switch. The workconserving property of the switch is independent of the switch size and input traffic pattern. We also present a suite of algorithms that can be used in combination with LOOFA. These algorithms determine the fairness and delay properties of the switch. We also describe a mechanism to provide delay bounds for real-time traffic using LOOFA. These delay bounds are achievable without requiring output-buffered switch emulation.

Hop-by-

Switch designs and the uniform distribution traffic pattern that has been the basis of much switch design analysis are discussed. In particular it is shown that head of line blocking is not the major cause of switch and link underutilization. Switch fabric and buffer system input bandwidth tradeoffs are described. For client server applications it is shown that having the majority of switch buffers on the input side of a switch reduces overall switch buffeting.