Network-on-Chip packet prioritisation based on instantaneous slack awareness

Arbitration policies and predictability enhancement measures typically employ packet priority as the decisive parameter. Though packet timeliness is a key attribute, Network-on-Chip designs rarely consider timeliness as a parameter mostly due to the impracticality of utilising time stamping which relay on the notion of a global time. In this paper, we introduce a low overhead approach where packets carry a slack value, which would notify the router of the latency the packet can suffer without any adverse effects. This would enable routers to service late packets (even lower priority ones) by trading the expendable time associated with the high priority packets hence improving overall quality of service. Utilising a Hardware Description Language coded prototype, we demonstrate the effectiveness of the technique and quantify the associated hardware overhead.