Optimizing Queueing Delay Budgets in DetNets based on Strict Priority Queueing
Jakob Miserez, Didier Colle, Mario Pickavet, Wouter Tavernier · 2025
Deterministic networks (DetNets) demand precise delay modeling to meet quality-of-service (QoS) requirements for time-sensitive applications. Queueing delay plays the most critical role among all contributors to end-to-end latency. Existing Time-Sensitive Networking (TSN) standards, such as Time-Aware Shaping (TAS) and Cyclic Queueing and Forwarding (CQF), rely on high-precision time synchronization to effectively manage queueing delays. Larger-scale DetNets suffer from less accurate time synchronization, resulting in alternative data plane approaches. The approach followed in this paper uses strict priority queueing (SPQ), network calculus (NC), and pre-configured queueing delay budgets to bound queueing delays and improve routing flexibility and simplicity. While it has been shown that queueing delay budget configurations affect routing efficiency, there are no studies on deriving optimal budgets. This paper addresses this gap by introducing a novel optimization model that jointly determines optimal flow routes and queueing delay budgets while leveraging NC to ensure delay compliance. The model is evaluated in an industrial setting, demonstrating its utility as a benchmark for routing solutions, and as a tool to identify scenarios in which SPQ can be beneficial and to derive queueing delay budget configurations for specific use cases. Moreover, the analysis highlights the differences between priorities and the importance of considering traffic demands, network topology, and capacity when fine-tuning the DetNet.