BPA: a fast packet scheduling algorithm for real-time switched Ethernet networks

In this paper, we present a MAC-layer packet scheduling algorithm, called BPA, for real-time switched Ethernet networks. BPA considers a message model where trans-node application-level messages have end-to-end timeliness requirements that are specified using Jensen´s benefit functions. The objective of BPA is to maximize the aggregate message-level benefit. The algorithm reasons that this objective can be achieved by maximizing aggregate packet-level benefit, where packets of messages are allowed to inherit benefit functions of their parent messages. BPA thus solves a non-preemptive packet scheduling problem. Since this problem is NP-hard, BPA heuristically computes packet schedules to maximize aggregate benefit, incurring a worst-case computational complexity of O(n²). This is better than the O(n³) complexity of the previously known best algorithm (called CMA) for the same problem. Further, our experimental studies show that BPA performs as good as CMA for a broad set of benefit functions, and significantly outperforms CMA for some benefit functions. Furthermore, we observe that BPA yields lower missed-deadline ratio than CMA when message arrival density increases.