The interleaved regulator (implemented by IEEE TSN Asynchronous Traffic Shaping) is used in time-sensitive networks for reshaping 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）用于时间敏感网络中，基于逐流合同对数据流进行整形。当应用于来自FIFO系统的聚合流时，采用初始合同进行整形的交错调节器不会增加聚合流的最高延迟。这种"免费整形"特性支持端到端时延上界的计算和网络时序要求的验证。建立网络元素特性的一种常用方法是获得网络演算服务曲线模型。针对交错调节器是否存在此类模型仍是一个悬而未决的问题。若能为其建立服务曲线模型，对该机制的分析将不再受"免费整形"适用场景的限制，从而拓展其在时间敏感网络中的应用。本文研究网络演算服务曲线能否表征交错调节器的行为。研究发现，置于"免费整形"要求之外（非FIFO系统之后）的交错调节器可能导致无界延迟。由此证明，不存在能够解释交错调节器行为的网络演算服务曲线。虽然仍可为交错调节器找到非平凡服务曲线，但其长期速率不足以提供任何保证（具体而言，对于处理至少四条相同合同数据流的调节器，任何服务曲线的长期速率上界仅为逐流合同速率的3倍）。