Schedule Time-Triggered Ethernet
K. I. Nikishin, Nikolas Konnov · 2020
It is described a method for transmitting Ethernet messages in a distributed real-time system that implements a cyclic control algorithm, in which there are many network nodes, at least one switch, connected to each other by communication channels, which provides forwarding between nodes of both normal Ethernet ET-frames (event-triggered traffic) that do not have strict delivery time restrictions, and hard real-time TT-frames (time-triggered traffic). The switch checks the moment when the TT-frame is received with a pre-known time window to determine whether it can be transmitted to the recipient, the TT-frames are delivered to the recipient at pre-scheduled times. For each moment of delivery of TT-frames specified in the schedule, the time of blocking the start of transmission of ET-frames is calculated, the value of which is determined by the maximum length of the ET-frame. For each moment of delivery of TT-frames specified in the schedule, the time of blocking the start of transmission of ET-frames is calculated, the value of which is determined by the maximum length of the ET-frame. The transfer of the ET-frame is allowed from the corresponding buffer of the switch's output port after each TT-frame is transmitted, provided that there is no blocking. The result is reduced frame delay in the network, increased network bandwidth, elimination of time conflicts between TT and ET-frames, and the ability to transfer multiple frames directed to different ports in a single time slot.