Quantitative Performance Comparison of Various Traffic Shapers in Time-Sensitive Networking

Owning to the sub-standards being developed by IEEE Time-Sensitive Networking (TSN) Task Group, the traditional IEEE 802.1 Ethernet is enhanced to support real-time dependable communications for future time- and safety-critical applications. Several sub-standards have been recently proposed that introduce various traffic shapers (e.g., Time-Aware Shaper (TAS), Asynchronous Traffic Shaper (ATS), Credit-Based Shaper (CBS), Strict Priority (SP)) for flow control mechanisms of queuing and scheduling, targeting different application requirements. These shapers can be used in isolation or in combination and there is limited work that analyzes, evaluates and compares their performance, which makes it challenging for end-users to choose the right combination for their applications. This paper aims at (i) quantitatively comparing various traffic shapers and their combinations, (ii) summarizing, classifying and extending the architectures of individual and combined traffic shapers and their Network calculus (NC)-based performance analysis methods and (iii) filling the gap in the timing analysis research on handling two novel hybrid architectures of combined traffic shapers, i.e., TAS+ATS+SP and TAS+ATS+CBS. A large number of experiments, using both synthetic and realistic test cases, are carried out for quantitative performance comparisons of various individual and combined traffic shapers, from the perspective of upper bounds of delay, backlog and jitter. To the best of our knowledge, we are the first to quantitatively compare the performance of the main traffic shapers in TSN. The paper aims at supporting the researchers and practitioners in the selection of suitable TSN sub-protocols for their use cases

A Theory of Traffic Regulators for Deterministic Networks with Application to Interleaved Regulators

We define the minimal interleaved regulator, which generalizes the Urgency Based Shaper that was recently proposed by Specht and Samii as a simpler alternative to per-flow reshaping in deterministic networks with aggregate scheduling. With this regulator, packets of multiple flows are processed in one FIFO queue; the packet at the head of the queue is examined against the regulation constraints of its flow; it is released at the earliest time at which this is possible without violating the constraints. Packets that are not at the head of the queue are not examined until they reach the head of the queue. This regulator thus possibly delays the packet at the head of the queue but also all following packets, which typically belong to other flows. However, we show that, when it is placed after an arbitrary FIFO system, the worst case delay of the combination is not increased. This shaping-for-free property is well-known with per-flow shapers; surprisingly, it continues to hold here. To derive this property, we introduce a new definition of traffic regulator, the minimal Pi-regulator, which extends both the greedy shaper of network calculus and Chang's max-plus regulator and also includes new types of regulators such as packet rate limiters. Incidentally, we provide a new insight on the equivalence between min-plus and max-plus formulations of regulators and shapers