Throttle and preempt: A flow control policy for real-time traffic in wormhole networks

Abstract

In this paper, we study wormhole routed networks and envision 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 even at a low network load. 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 for various real-time traffic configurations without extra virtual channels. It is also observed that the throttle and preempt flow control offers shorter delay for non-real-time traffic than the existing real-time flow control does. (C) 1999 Elsevier Science B.V. All rights reserved.