$\mu$TAS: Design and implementation of Time Aware Shaper on SmartNICs to achieve bounded latency

Abstract

Time-Aware Shaper (TAS) is a time-triggered scheduling mechanism that ensures bounded latency for time-critical Scheduled Traffic (ST) flows. The Linux kernel implementation (a.k.a TAPRIO) has limited capabilities due to varying CPU workloads and thus does not offer tight latency bound for the ST flows. Also, currently only higher cycle times are possible. Other software implementations are limited to simulation studies without physical implementation. In this paper, we present $\mu$TAS, a MicroC-based hardware implementation of TAS onto a programmable SmartNIC. $\mu$TAS takes advantage of the parallel-processing architecture of the SmartNIC to configure the scheduling behaviour of its queues at runtime. To demonstrate the effectiveness of $\mu$TAS, we built a Time-Sensitive Networking (TSN) testbed from scratch. This consists of multiple end-hosts capable of generating ST and Best Effort (BE) flows and TSN switches equipped with SmartNICs running $\mu$TAS. Time synchronization is maintained between the switches and hosts. Our experiments demonstrate that the ST flows experience a bounded latency of the order of tens of microseconds.