Software-defined Network Timing Technology Research

With the rapid development of different industries and technologies,network timing has become a challenge not only for scientific research but also for industrial networks.For emerging critical infrastructure,the demand for network timing has been growing rapidly,and more and more industries and applications have increased the requirements for network timing;in addition to the synchronization accuracy requirements,when building time synchronization systems,The economic cost of synchronous network construction,the complexity of the equipment,and the difficulty of implementing the synchronization algorithm need to be comprehensively considered,which undoubtedly poses a severe challenge to the existing time synchronization network.However,the existing network time synchronization schemes have problems such as limited accuracy,inflexible network structure,and high equipment costs,which make it difficult to meet increasing requirements.Software Defined Network(SDN),as a new type of network architecture,can define and control the network through software programming.Its control plane and data plane are separate,open and programmable.It provides a new idea for network time synchronization.After identifying the research topics,in order to solve the problems above,the paper mainly completed the following work:(1)Investigated related research on software-defined timing.Determine the meaning of time synchronization and timing,and classify the current commonly used timing methods,and conduct research around network time synchronization and precision time protocol.At the same time,the related research of software-defined timing is investigated,including the basic concepts of software-defined network,and the research progress of software-defined time synchronization at home and abroad,and the common points and differences of the various schemes mentioned in the research progress are summarized.(2)Based on the research of software-defined timing,a software-defined network timing scheme is proposed.The solution includes a software-defined timing network architecture.The synchronous network architecture is vertically divided into three planes:the application plane,the control plane,and the data plane.Based on the control plane's centralized control of the data plane and the clock compensation principle,control-data is designed.The flat interface implements the upload of time data of switching nodes by extending the OpenFlow protocol.The time controller calculates compensation values based on the global network view obtained by the network controller and the time data uploaded by the switching nodes to improve timing accuracy.(3)In the realization of the specific scheme,a synchronization compensation method based on time stamp is designed and implemented.Firstly,the composition of asymmetric delay is analyzed.For the non-deterministic asymmetric delay introduced by the switching node,a dwell time measurement method based on timestamp is proposed.Based on this method,the exchange supporting measurement of dwell time is designed.node.The designed switching node measures the dwell time of the uplink and downlink synchronization messages passing through the switching node,and uploads it to the time controller for calculation and compensation.Considering the stability of the compensated clock,the compensation value should be processed by an algorithm.Experiments are carried out on this basis,and the results of algorithmless processing,fixed value PID filtering algorithm processing and neural network based PID filtering algorithm processing are compared.The results show that the accuracy of time synchronization is effectively improved after using the compensation algorithm.Finally,the two algorithms are further compared and analyzed.