The interleaved regulator (implemented by IEEE TSN Asynchronous Traffic Shaping) is used in time-sensitive networks to reshape the flows with per-flow contracts. When applied to an aggregate of flows that come from a FIFO system, an interleaved regulator that reshapes the flows with their initial contracts does not increase the worst-case delay of the aggregate. This shaping-for-free property supports the computation of end-to-end latency bounds and the validation of the network's timing requirements. A common method to establish the properties of a network element is to obtain a network-calculus service-curve model. The existence of such a model for the interleaved regulator remains an open question. If a service-curve model were found for the interleaved regulator, then the analysis of this mechanism would no longer be limited to the situations where the shaping-for-free holds, which would widen its use in time-sensitive networks. In this paper, we investigate if network-calculus service curves can capture the behavior of the interleaved regulator. We find that an interleaved regulator placed outside of the shaping-for-free requirements (after a non-FIFO system) can yield unbounded latencies. Consequently, we prove that no network-calculus service curve exists to explain the interleaved regulator's behavior. It is still possible to find non-trivial service curves for the interleaved regulator. However, their long-term rate cannot be large enough to provide any guarantee (specifically, we prove that for the regulators that process at least four flows with the same contract, the long-term rate of any service curve is upper-bounded by three times the rate of the per-flow contract).

翻译：交错调节器（由IEEE TSN异步流量整形实现）用于时间敏感网络，通过逐流契约对流进行整形。当应用于来自FIFO系统的聚合流时，采用初始契约对流进行整形的交错调节器不会增加聚合流的最坏情况延迟。这种“免费整形”特性支持端到端延迟边界的计算与网络时序要求的验证。建立网络元素特性的常用方法是获取网络演算服务曲线模型。交错调节器是否存在此类模型仍是一个开放问题。若能为交错调节器建立服务曲线模型，则对该机制的分析将不再局限于满足“免费整形”条件的场景，从而拓展其在时间敏感网络中的应用。本文探究网络演算服务曲线能否描述交错调节器的行为。研究发现，置于“免费整形”要求之外（即非FIFO系统之后）的交错调节器可能导致无界延迟。因此，我们证明不存在任何网络演算服务曲线能解释交错调节器的行为。虽然仍可为交错调节器构造非平凡服务曲线，但其长期速率不足以提供任何保障（具体而言，我们证明对于处理至少四条具有相同契约流的调节器，任何服务曲线的长期速率上限仅为逐流契约速率的三倍）。