This paper focuses on characterizing the promises and potential of the third, and most recent, revision of BBR—introduced to the public in July 2023.
PAM 2024Revisiting ECN adoption in the modern Internet, revealing widespread support alongside persistent ECN bleaching by hosts, middleboxes, and major networks.
TMA 2026TCP Prague is a congestion control algorithm (CCA) for the low latency, low loss and scalable throughput (L4S) architecture, which targets very low queuing delay by leveraging fine-grained explicit congestion notification (ECN) signals to adjust its sending rate. Most prior evaluations focus on high rate scenarios and TCP friendliness. However, Prague may operate over low bandwidth bottlenecks or compete with elastic and inelastic flows, leaving only a small fair share per flow. In such cases, Prague reduces its segment size to maintain approximately two packets per virtual round trip time (RTT). The current design derives the segment size from both the pacing rate and RTT, making it sensitive to noisy RTT conditions and potentially affecting performance. We redesign segment sizing to depend solely on the pacing rate and implement three schemes—linear, exponential, and logarithmic. We implement these schemes in a modified Prague kernel and evaluate them in our testbed against both the default Prague segment-sizing algorithm and a fixed-segment-size baseline. On throttled links, our schemes reduce retransmissions by more than a factor 20 and increase feedback granularity. Under both elastic (inter- and intra-CCA) and inelastic competition, they achieve improve throughput stability and fairness.
@inproceedings{zeynali2026l4s,
title = {Small Packets, Big Difference: L4S Congestion Control at Low Bandwidth},
author = {Zeynali, Danesh and Chang, Chia-Yu and De Schepper, Koen and Chandrasekaran, Balakrishnan and Feldmann, Anja},
booktitle = {Proceedings of the Applied Networking Research Workshop (ANRW)},
year = {2026},
url = {https://inet-l4s.mpi-inf.mpg.de/}
}