Switch real-time industrial Ethernet with mixed scheduling policy

There is a strong interest of using the cheap and simple Ethernet technology for industrial network control system. However, the lack of real-time services has prevented this change of used network technology. In order to realize real-time communication over Ethernet in industrial application, one must be able to bound the medium access time within an acceptable limit. But the multiple access nature of Ethernet makes it impossible to guarantee a deterministic medium access time. In this paper, we introduce the IEEE 802.1p queuing feature in full-duplex switches, and propose a mixed scheduling policy (MSP) for the lay 2 switches in Ethernet. MSP adopts different scheduling policy for different real-time requirements frames. The objective is mainly to study the worst-case response time for real-time periodic frames and the mean delay time for time-critical aperiodic frames by setting the appropriate frames priority to meet the industrial application.