交换式以太网中周期性固定优先级消息的可调度性分析

Schedulability Analysis of Periodic Fixed Priority Messages over Switched Ethernet

为使交换式以太网能满足工业数据通信的实时性要求,首先提出了一种基于固定优先级调度(FixPriority Scheduling,FPS)的实时消息调度模型,由源站点和消息接纳控制服务器对消息进行可调度性判定.另外,通过将消息集在交换式以太网上的可调度性判定转化为对在接收链路上具有释放抖动消息集的可调度性分析问题,给出了实时消息在发送和接收链路最坏传输完成时间的计算公式,进而提出了消息可调度性判定方法,并对相关结论进行了理论证明.

To support the required time constrained communications in industrial communications, an improved message transmission model in which switch and the end-nodes control the real-time traffic with Fix-Priority Scheduling （FPS） and the feasibility analysis is performed by the source nodes and the Message Adopt Control Server without the modification of the operational features of Ethernet switch was proposed. Moreover, by converting the schedulability analysis of messages set over switched Ethernet to the problem of analysis of messages set with release jitter on downlink of switch, equations to compute the worst case time for real-time messages to finish transmission on the uplink and downlink of switch were developed, and then a feasibility analysis method for real-time periodic messages over switched Ethernet was given. Some important conclusions were also proved by using real-time theory.