AuthorsN. Khademi, M. Welzl, G. Armitage, C. Kulatunga, D. Ros, G. Fairhurst, S. Gjessing and S. Zander
TitleAlternative Backoff: Achieving Low Latency and High Throughput with ECN and AQM
Afilliation, , Communication Systems
Project(s)The Center for Resilient Networks and Applications
Publication TypeTechnical reports
Year of Publication2015
Date Published07/2015
PublisherCentre for Advanced Internet Architectures (CAIA), Swinburne University of Technology
Place PublishedMelbourne, Australia

CoDel and PIE are recently proposed Active Queue Management (AQM) mechanisms that minimize the time packets spend enqueued at a bottleneck, instantiating shallow, 5 ms to 20 ms buffers with short-term packet burst tolerance. However, shallow buffering causes noticeable TCP performance degradation when a path’s underlying round trip time (RTT) heads above 60ms to 80ms (not uncommon with cross-continental and inter-continental traffic). Using less-aggressive multiplicative backoffs is known to compensate for shallow bottleneck buffering. We propose ABE: “Alternative Backoff with ECN”, which consists of enabling Explicit Congestion Notification (ECN) and letting individual TCP senders use a larger multiplica- tive decrease factor in reaction to ECN-marks from AQM- enabled bottlenecks. Using a mix of experiments, theory and simulations with standard NewReno and CUBIC flows, we show significant performance gains in lightly- multiplexed scenarios, without losing the delay-reduction benefits of deploying CoDel or PIE. ABE is a sender- side-only modification that can be deployed incrementally (requiring no flag-day) and offers a compelling reason to deploy and enable ECN across the Internet.

Citation Keyabe-caia-2015

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