Throttle and preempt: a new flow control for real-time communications in wormhole networks

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 uncontrolled 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 dramatically 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.