Optimization Of Switching Mechanism And Delay Analysis In Time-sensitive Networks

The deterministic delay boundary is an urgent need for the intelligent sustainable devel-opment in the intelligent network connection automobile industry.Time-sensitive network（TSN）is a new framework introduced to serve these applications.As the communication backbone of intelligent connected vehicles,TSN needs to deal with a large number of mes-sage flows.In the worst case,assigning a large number of TT（Time-triggered）message flows to a single FIFO queue results in a long blocking delay.This requires the allocation of multiple FIFO queues for TT traffic flows,following the IEEE 802.1 standard protocol^[1],and GCL（Gate Control List）that retains a static configuration may not benefit much.If the time window configured by GCL continues to be determined by considering the flow cate-gory of its own queue,there may be competition among multiple FIFO queues of the same first-class category,which undermines timing guarantee and deterministic transmission,and requires complex delay boundary analysis for each traffic flow in this case.In essence,GCL restricts high-priority queues and supports low-priority queues.It must be wisely designed to improve or at least not lose performance.In addition,GCL is a very rigid mechanism that is difficult to handle burst traffic or jitter.In order to solve this research challenge,we plan to optimize the structure of the existing TSN switch and analyze the delay boundary of each flow class in the optimized TSN switch.It has a certain theoretical guiding significance for the design and implementation of TSN switch,so that it can adapt to the network environ-ment of intelligent network-connected vehicles.The specific innovation work of this paper is as follows:（1）A TSN switch mechanism without GCL mechanism is proposed,which allocates multiple FIFO queues to the TT traffic and the AVB（Ethernet Audio/Video Bridging）traffic,so that the contention between multiple TT queues is resolved first.At this point,eight FIFO queues per port compete for transmission rights based on strict priority.Then the delay boundary analysis of multiple TT queues（that is,all TT traffic flow）is carried out to ensure their deterministic transmission,and a delay reachability technique is proposed for the delay boundary analysis of TT T2 traffic,which can obtain secure and pessimistic delay boundaries.Finally,it is proved that the delay boundary obtained by the proposed delay reachability technique is definite,predictable and safe.（2）In order to achieve transmission balance,a Credit-based Shaper（CBS）mechanism is introduced into each AVB A and B queue,which takes precedence over priority,to solve the contention problem between AVB queues.Then it analyzes the circumstances in which the interference delay between AVB A traffic and AVB B traffic is the largest.Finally,based on the delay reachability technique,the delay boundary analysis of AVB A hand B traffic is carried out respectively.（3）Three experiments are carried out to study the influence and characteristics of dif-ferent FIFO queue sizes on the delay boundary of each flow class,the influence factors and characteristics of the interference delay between the AVB A and AVB B traffic,and the influence and law of the transmission slope and idle slope in the credit function on the delay boundary of the AVB A and B traffic flow.The paper mainly conclude that the delay boundaries of TT traffic flows are fixed and predictable.At the same time,it is verified that different delay boundaries of AVB flows can be obtained by changing the credit function.