omitted for review

@inproceedings{Example, title={Example}, author={Example} booktitle={Example}, year={2026}, organization={IEEE} }

In datacenters, lossless network is very attractive as it can achieve ultra-low latency. In commodity Ethernet, lossless forwarding is achieved by hop-by-hop Priority-based Flow Control (PFC). To avoid buffer overflow, PFC-enabled switches need to reserve some buffer as headroom, absorbing in-flight packets during the delay for back-pressure messages to take effect. However, with the growing link speed in production networks, the buffer becomes increasingly insufficient, and the headroom can occupy a considerable fraction of buffer. As a result, the remaining buffer for absorbing normal traffic bursts is significantly squeezed, leading to frequent PFC messages that degrade the network performance. Worse yet, we find that the current static and queue-independent headroom allocation scheme is quite inefficient, resulting in significant buffer wastage. In light of this, we propose Dynamic and Shared Headroom allocation scheme (DSH), which dynamically allocates headroom to congested queues and enables sharing of allocated headroom among different queues. To achieve this, DSH first introduces port-level flow control, which performs flow control at the granularity of individual ports, guaranteeing lossless forwarding with a small fraction of per-port headroom. With this lossless guarantee, the switch is liberated for dynamic headroom adjustment. DSH dynamically allocates per-queue headroom based on the congestion status of each queue. Meanwhile, DSH preserves the queue- level flow control to protect the non-congested queues from being paused by congested queues, ensuring performance isolation on buffer sharing. Extensive experiments and simulations show that DSH can absorb 14× more bursts without triggering PFC messages and reduce the flow completion time by up to ∼31%.

@ARTICLE{11131478, author={Shan, Danfeng and Ma, Jinchao and Li, Yunguang and Hu, Boxuan and Zhang, Tong and Tang, Yazhe and Li, Hao and Wang, Jinyu and Zhang, Peng}, journal={IEEE Transactions on Networking}, title={Efficient Headroom Allocation With Two-Level Flow Control for Lossless Datacenter Networks}, year={2025}, pages={1-16}, keywords={Flow production systems;Resource management;Switches;Packet loss;Delays;Buffer overflows;Uplink;System-on-chip;System recovery;Propagation losses;Priority-based flow control;bursty traffic;buffer management}, doi={10.1109/TON.2025.3596437}}