Research On Traffic Scheduling Technology In Time-sensitive Network

With the rapid development of information technology,applications such as real-time control,immersive interaction and edge computing have put forward the need for deterministic transmission with low delay and low jitter.In the future,there will be more business needs for millisecond or even microsecond delay in the network.Driven by the demand of these scenarios with high requirements for data transmission,real-time reliable transmission of data has become extremely important.However,the best-effort packet forwarding mechanism adopted by traditional Ethernet has a long tail delay effect,which is difficult to meet the requirements of bounded low delay in the above time-sensitive service scenarios.Time-Sensitive Network(TSN),as a new network data transmission technology,allows multiple types of traffic,such as time-sensitive traffic and best-effort traffic,to be transmitted together on the same network.By globally planning and scheduling different types of traffic and eliminating conflicts on outgoing ports,the TSN system ensures deterministic transmission requirements of time-sensitive traffic in terms of delay,jitter,and reliability.However,the current traffic scheduling in TSN has the following problems:(1)The separation of time-sensitive traffic scheduling and routing leads to the contention of time slot for multiple time-sensitive traffic;(2)The scheduling scheme cannot be solved dynamically and effectively in the face of newly arrived time-sensitive traffic requests in TSN;(3)Slot preemption and scheduling conflict are easy to occur when time-sensitive traffic and non-time-sensitive traffic are transmitted on the common network.To solve the above problems,this thesis starts from two perspectives of time-sensitive traffic scheduling in TSN and mixed scheduling of multi-types of traffic,and carries out related research on traffic scheduling technology in time-sensitive networks,and proposes corresponding solutions.The main work and innovation of this paper are as follows:(1)Aiming at the problem of slot contention of multiple time-sensitive traffic in TSN caused by time-sensitive traffic scheduling and route separation,a traffic scheduling method based on joint route planning was proposed.Based on the inter-flow conflict degree of time-sensitive traffic,the proposed method flexibly allocates traffic routes.On this basis,the scheduling constraint model of time-aware shaping and joint conflict-free routing is established,which strictly guarantees the bounded low delay requirement of time-sensitive traffic scheduling in two dimensions of time and space.Experimental results show that the proposed method has good delay performance in different topology scenarios.When the time sensitive traffic deployed in TSN increases gradually,the average end-to-end delay increases in the range of 60μs,and the maximum fluctuation of the worst end-to-end delay is only 7.18%.While ensuring the balanced load of the link,it effectively reduces the delay caused by congestion conflicts,which is suitable for all kinds of time-sensitive traffic scale.(2)To solve the problem that the scheduling scheme cannot be dynamically and efficiently solved when the new time-sensitive traffic requests arrive in time-sensitive networks,a dynamic response incremental scheduling method for time-sensitive traffic in TSN was proposed.The incremental scheduling process of time-sensitive traffic is analyzed by using software-defined time-sensitive network architecture.On the premise of meeting the demand of traffic scheduling,two modes of traffic shift and traffic exchange were used to dynamically adjust the slot injection position of the original scheme,and the sending offset time of the new time-sensitive traffic was determined to minimize the global traffic transmission jitter.The evaluation results show that,compared with the global rearrangement scheduling method,the transmission jitter is reduced by60.34%,and the significant increase of traffic jitter in incremental scheduling is effectively controlled without affecting the transmission delay,thus realizing the dynamic incremental scheduling of time-sensitive traffic in TSN.(3)Aiming at the problems such as slot preemption and scheduling conflict in the common network transmission of time-sensitive and non-time-sensitive traffic in TSN,a least laxity first hybrid traffic scheduling method combining time-aware shaping(TAS)and cyclic queuing and forwarding(CQF)mechanism was proposed.Firstly,a TAS and CQF collaborative scheduling framework for mixed traffic is established.Then,a traffic shaping method based on the lowest relaxation priority is designed,which adaptively determines and dynamically arranges the slot injection sequence of different types of traffic combined with the traffic characteristics.Finally,traffic schedulability is evaluated based on scheduling constraints of different types of traffic.The simulation results show that,compared with the existing scheduling strategies,the proposed mixed traffic scheduling strategy can improve the slot injection rate by 24.3% and schedule more non-time sensitive traffic on the basis of ensuring the successful scheduling of time-sensitive traffic.Moreover,it can achieve good delay performance for periodic non-time sensitive traffic in mixed traffic scenarios with different traffic proportions.