交换以太网中实时消息截止期划分算法研究

Research on deadline partitioning schemes for real-time message transmission over switched Ethernet

为解决交换式以太网中实时消息在发送及接收链路上的截止期划分问题,首先给出了非抢占式EDF调度算法的可调度性分析方法,并分析了消息的提前释放对非抢占式EDF调度算法可调度性的影响,在此基础上提出了新的截止期划分算法(MDPS)。算法通过计算可满足调度条件时消息在发送链路及接收链路截止期应该划分的下限,并结合截止期的松驰量实现实时消息在发送及接收链路上的截止期划分。算法实验比较和分析表明,该算法在提高网络聚合带宽、减小消息的错失率方面明显优于现有的ADPS算法。

To solve the problem of dividing deadlines of real-time channels between the in and outgoing link to/from the switch when applying switched Ethernet in real-time industrial communications,this paper presented an improved feasibility analysis method for periodic real-time messages scheduled by non-preemptive EDF algorithm.In addition,the schedulability analysis of real-time periodic messages when instances of messages were early released was given and proved by using real-time scheduling theory.Particularly,based on an algorithm for calculating the minimum non-preemptive EDF-feasible deadline of real-time messages,it developed a novel scheme of asymmetrically dividing deadlines of real-time channels between the in and outgoing link to/from the switch（MDPS）.By computing the minimum non-preemptive EDF-feasible deadline of real-time message on the in and outgoing link to/from the switch and combing the slack value of deadline,MDPS could optimize deadline partitioning of real-time channels between the in and outgoing link to/from the switch.The scheme was compared with ADPS.The simulations show that the MDPS performs better than the ADPS in terms of using the aggregated switch throughput and the missing rate of message.