A Design Of Synchronous And Definable Ethernet For Real-time System

As the industrial Ethernet is widely used in many fields nowadays,the problems of high latency,low reliability,congestion and packet loss are increasingly prominent.This paper is going to design and realize a synchronous Ethernet for real-time control system,aiming at providing a way to improve the performance of industrial Ethernet.The Ethernet in this paper involves the time synchronization and data flows concept which reference to Time Sensitive Network and Software Defined Network.This paper adopts the IEEE 1588 based Precisiong Time Protocol(PTP)as the synchronization protocol.The Open vSwitch virtual exchange technology is also adopted to forward network messages.The data flows in Open vSwitch can be controled by SDN controller in Open Flow protocol dynamicly or triggered by the synchronous time staticly.The main work of this paper includes these following four parts:1)We analyzed and modeled the Pricision Time Protocol daemon(PTPd).Then we optimized the filter of PTPd according to the synchronization model.Finally,it was transplanted into an embedded system and the point to point synchronization accuracy was below 10ns;2)We designed the end node PCB and the upper computer software based on Xilinx Zynq FPGA.The timing correction module was implemented in the Programmable Logic side of FPGA to provide timing,correction and time triggering functions required by PTP daemon;3)Switching node PCB was designed based on Xilinx Zynq FPGA.Functions such as PTPd2,Open vSwitch and Openflow were realized by a customized Linux system to support time synchronization and forwarding by SDN flows.4)Network time synchronization,SDN flows and network latency were tested by a verification system.The results show that the single-point synchronization accuracy can reach about 30 ns.The link delay can be reduced by 77% with the SDN switch,and it can be further reduced by 27% with the static SDN flows triggered by time.