Throttle and Preempt: A New Flow Control for Real-Time Communications in Wormhole Networks

In this paper, we study wormhole routed networks and their suitability for real-time traffic in a priority-driven paradigm. A traditional blocking flow control in wormhole routing may lead to a priority inversion in the sense that high priority packets are blocked by low priority packets for unlimited time. This uncon-trolled priority inversion causes the frequent deadline missing. This paper therefore proposes a new flow control called throttle and preempt flow control, where high priority packets can preempt network resources held by low priority packets, if necessary. As a result, this flow control does not cause priority inversion. Our simulations show that the throttle and preempt flow control dramat-ically reduces deadline miss ratio without extra virtual channels. It is also observed that the throttle and preempt flow control offers shorter delay for non-real-time traffic than existing real-time flow control does.