Multihop Control Schemes in Switches With Reconfiguration Latency

Optical switching fabrics (OSFs) are receiving increasing attention in the design of high-speed packet switches, due to their excellent properties in terms of available bandwidth and reduced power consumption. However, for most optical devices, the latency needed to reconfigure input/output switch port connections may not be negligible with respect to the packet transmission time and can adversely affect switch performance, creating high delays and reduced throughput. We consider OSFs, and we propose a multihop approach to schedule packet transfers; i.e., packets are sent to the final destination port by exploiting transmission through intermediate ports. We show that the multihop approach is a promising technique to control the trade-off between delay and throughput, and it permits us to partly decouple the switch reconfiguration rate from the packet duration. We propose a general framework to solve the issue of multihop transmission in input-queued packet switches. Furthermore, we examine the multihop approach when the direct exchange of packets among ports is based on multidimensional regular topologies. We discuss which sequence of intermediate ports should be traversed to reach the final output port (i.e., the internal routing) and the switch time-scheduling problem (i.e., when a pair of ports can exchange packets). Performance is analyzed both analytically and by simulation.