Research On Traffic Shaping Mechanisms Of Time-sensitive Networking

With the advent of the fourth industrial Revolution led by intelligent manufacturing,intelligent factories are developing rapidly,and the number of intelligent devices in factories is increasing day by day.Industrial Internet requires the network to provide bounded low delay jitter,high reliability,ubiquitous communication connection to meet the needs of industrial communication such as production control.Although industrial Ethernet can meet the demand of real-time communication,it has many problems such as protocol,standard incompatibility and speed limitation.Time-sensitive Networking(TSN)provides bounded low-latency jitter and high reliability communication services through enhanced functions based on Ethernet.The key technologies of TSN include time synchronization,traffic control,reliability assurance and resource control.Traffic shaping is a measure to adjust the output rate of traffic actively,and is one of the key technologies of TSN traffic control.TSN traffic shaping not only needs to achieve the goal of traffic rate limitation,but also needs to meet the deterministic delivery requirements.The TSN traffic shaping mechanism is classified into synchronous and asynchronous modes.As the main traffic shaping technology,The Cyclic Queuing and Forwarding(CQF)mechanism and its asynchronous extension Paternoster mechanism have advantages of low jitter,deterministic end-to-end delay,and low construction cost compared with other TSN traffic shaping technologies.However,CQF and Paternoster mechanisms have problems of low resource utilization and high packet loss rate respectively,so they are not suitable for intelligent factory applications with mixed traffic coexistence.In order to improve the utilization rate of traffic shaping resources and reduce the end-to-end delay and packet loss rate of time-sensitive traffic,this thesis studies the extension of CQF and Paternoster mechanism.The specific research contents are as follows:In order to solve the problems of low bandwidth utilization and poor global schedulable of CQF,a Time Slot-Aware Cyclic Queuing and Forwarding(TSA-CQF)mechanism was proposed based on CQF.TSA-CQF improves bandwidth utilization by inserting low-priority traffic into the remaining available time slots in the CQF parity queue for transmission.TSA-CQF performs traffic shaping on the outbound gating of CQF queues and inserts non-time-sensitive traffic into time-sensitive traffic queues for transmission.Then,the global traffic planning is carried out,and the multi-constraint objective optimization problem is solved by simulated annealing algorithm.The scheduling strategy is obtained to complete the global traffic scheduling,improve the number of TSA-CQF dispatchable flows,further improve the utilization rate of resources,and reduce the end-to-end worst delay of time-sensitive traffic(time-sensitive flow).The simulation results show that compared with the standard CQF mechanism,the average end-to-end worst delay of time-sensitive flow is reduced by 37.45% under different network loads,and the average bandwidth utilization is increased by 11.29%.In order to solve the problem of high packet loss rate in asynchronous traffic shaping,an Adaptive Shaper-Paternoster(AS-Paternoster)based traffic shaping mechanism was proposed.As-paternoster consists of two parts: adaptive flow regulation and cycle flow out.Adaptive traffic regulation is that the adaptive traffic regulator classifies the First In First Out(FIFO)traffic by priority,selects different queue entry policies under different network loads,and transmits the traffic to the Paternoster queue.Periodic traffic dequeuing refers to the data entering the Paternoster queue.Prior,Current,Next,and Last queues are cycled periodically to transfer data in a fixed period,ensuring the deterministic delivery of time-sensitive traffic and reducing the packet loss rate of the time-sensitive network in asynchronous state.Compared with the standard Paternoster mechanism,the average end-to-end worst delay of time-sensitive flow is reduced by 10.22% under different network loads,and the average packet loss rate of time-sensitive flow is reduced by 13.28%.In summary,starting from TSN traffic shaping and taking intelligent factory network as the background,TSA-CQF mechanism is firstly proposed to effectively improve the bandwidth utilization of time-sensitive network and reduce the end-to-end worst delay of time-sensitive flow.Then,the AS-Paternoster mechanism is proposed,which effectively reduces the packet loss rate of time-sensitive networks in asynchronous state,and realizes the deterministic and reliable delivery of time-sensitive traffic.It lays the theoretical and technical foundation for the application of time-sensitive network in the future intelligent factory.