Push-In First-Out (PIFO) offers a unified abstraction for rapidly deploying diverse scheduling algorithms on the same hardware. As SerDes-lane aggregation pushes port rates to 1.6 Tbps, the perpacket processing budget is at a sub-nanosecond scale, making single-queue PIFO designs fail to keep up. Mirroring lane aggregation, we advocate interleaving multiple PIFO queues. However, simple round-robin parallelization introduces substantial scheduling error, and in the worst case, it can grow to the order of the buffer size.

Programmable packet scheduling enables the integration of scheduling algorithms into switches without the need for hardware redesign. The Push-In First-Out (PIFO) queue facilitates a programmable packet scheduler, supporting a single scheduling algorithm flexibly. However, hierarchical scheduling required in Multi-Tenant Data Centers (MTDCs) remains non-programmable. Dynamic and diverse hierarchical scheduling algorithms necessitate alterations in both the number of PIFO queues and their connection topology, posing a significant challenge to support them on fixed hardware.

Push-In-First-Out (PIFO) queue has been extensively studied as a programmable scheduler. To achieve accurate, large-scale, and high-throughput PIFO implementation, we propose the Balanced Multi-way (BMW) Sorting Tree for real-time packet sorting. The tree is highly modularized, insertion-balanced and pipeline-friendly with autonomous nodes.