Determination of Delay Bound over Multi-hop Real-Time Switches with Virtual Output Queuing

Predictable and guaranteed response is an essential characteristic of safety-critical real-time systems. Thus we need to guarantee that the end-to-end latency of data exchange within such a system is always bounded and controlled, so that the overall system behavior is predictable and safe. In this paper, we propose a method for determining the worst-case delay when a packet traverses a network that consists of real-time crossbar switches. These switches guarantee that any feasible traffic can be switched in two clock periods by adopting an optimal clearance-time switching policy together with clock-driven scheduling. We also propose a switching architecture that introduces a delay buffer and virtual output queues to meet the one-shot traffic assumption required for optimal clearance-time switching. By removing the impractical assumptions made in previous works, we are able to derive a more accurate delay bound for real-world scenarios.