Investigating the Impact of ACK Aggregation on TCP Performance using ns-3
Evaluation of Transport and MAC-Layer Aggregation Techniques
H. Heinczinger (TU Delft - Electrical Engineering, Mathematics and Computer Science)
FA Kuipers – Mentor (TU Delft - Networked Systems)
A. Zapletal – Mentor (TU Delft - Networked Systems)
A Katsifodimos – Graduation committee member (TU Delft - Data-Intensive Systems)
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Abstract
Modern TCP congestion control algorithms rely on timely ACK feedback to adjust their parameters. However, some networks deliberately suppress ACKs. This study uses the ns-3 simulator to experiment with the impact of suppressing ACKs on the reverse path on four TCP variants (BBRv3, Cubic, NewReno, Vegas) in both wired and wireless dumbbell topologies. In wired experiments, we implement a custom queue that allows us to test fixed aggregation ratios at the transport-layer. In wireless scenarios, we utilize the IEEE 802.11n standard’s MAC-layer aggregation schemes (A-MSDU, A-MPDU), both individually and in combination, and also evaluate varying maximum A-MPDU aggregation sizes. Our results show that while transport-layer aggregation can degrade performance and fairness, especially for BBRv3 and Cubic, MAC-layer aggregation consistently improves throughput without destabilizing TCP behaviour. NewReno demonstrates strong resilience across both setups, while Vegas exhibits highly inconsistent performance. These findings highlight the importance of aligning aggregation
mechanisms with congestion control strategies carefully.