Asynchronous Time-Aware Shaper for Time-Sensitive Networking

Abstract

The Time Sensitive Networking Task Group of the IEEE 802.1 Working Group has developed a number of enhancements to the priority queueing architecture used by Ethernet. Perhaps the most notable one is the time-aware shaper (TAS), which can perfectly isolate priority classes in time with periodically scheduled traffic gates, thereby enabling ultra low latency applications to coexist with lower priority traffic on the same network. It requires near-perfect clock synchronization across the entire network, though, and a central network controller to calculate the timings for the traffic gates, based on known propagation delays on the network links. As a cheaper alternative, we have developed the asynchronous TAS that needs no clock synchronization, network planning, or a central controller. It uses local processes at each switch port to track the high priority streams, predict the arrival times of their next frames, and control the traffic gates such that the low priority streams are not interfering. We show how a simple predictor with minimal computation requirements can be used to track the high priority streams, and we demonstrate via simulations that this gating mechanism can protect the high priority traffic from interference.