Dynamic Per-Flow Queues in Shared Buffer TSN Switches
Wenxue Wu, Tong Zhang, Zhen Li, Xiaoqin Feng, Liwei Zhang, Fengyuan Ren · ACM Transactions on Design Automation of Electronic Systems · 2025
Time-Sensitive Networking (TSN), as an enhancement based on Ethernet, can ensure deterministic traffic transmission with low delays and minimal jitters. However, TSN switches have only eight priority queues inherited from Ethernet at each egress port, which limits the flexibility and efficiency of traffic scheduling, as well as the support for developing traffic management mechanisms. Although per-flow queues boost scheduling and Quality of Service (QoS), static per-flow hardware queues in switches are considered unpractical due to resource limits. In this article, we leverage the limitation of buffer size on the number of concurrent flows in shared buffer TSN switches to design Dynamic Per-Flow Queues (DFQ). DFQ only maintains a fixed number of virtual queues determined by the buffer size and dynamically manages the mapping between virtual queues and active flows to provide the capability of per-flow queuing. By constructing Flow Mapping Table (FMT) with content-addressable memory (or hash bucket), DFQ can quickly match, create, and recycle queues to multiplex limited switch resource. We prototype DFQ on an FPGA switch and evaluate its performance in different scenarios. Experimental results show that DFQ can decrease the overhead of per-flow isolation with minimal impact on delay and throughput, indicating that DFQ is an effective per-flow queues solution.