Murdoch University Research Repository

Welcome to the Murdoch University Research Repository

The Murdoch University Research Repository is an open access digital collection of research
created by Murdoch University staff, researchers and postgraduate students.

Learn more

Alternative backoff: Achieving low latency and high throughput with ECN and AQM

Khademi, N., Armitage, G., Welzl, M., Zander, S., Fairhurst, G. and Ros, D. (2017) Alternative backoff: Achieving low latency and high throughput with ECN and AQM. In: 2017 IFIP Networking Conference (IFIP Networking) and Workshops, 12 - 16 June 2017, Stockholm, Sweden

Link to Published Version:
*Subscription may be required


A number of recently proposed Active Queue Management (AQM) mechanisms instantiate shallow buffers with burst tolerance to minimise the time that packets spend enqueued at a bottleneck. However, shallow buffering causes noticeable TCP performance degradation as a path's underlying round trip time (RTT) heads above typical intra-country levels. Using less-aggressive multiplicative backoffs in TCP can compensate for shallow bottleneck buffering. AQM mechanisms may either drop packets or mark them using Explicit Congestion Notification (ECN), depending on whether the sender marked packets as ECN-capable. While a drop may therefore stem from any type of queue, an ECN-mark indicates that an AQM mechanism has done its job, and therefore the queue is likely to be shallow. We propose ABE: “Alternative Backoff with ECN”, which consists of enabling ECN and letting individual TCP senders back off less aggressively in reaction to ECN-marks from AQM-enabled bottlenecks. Using controlled testbed experiments with standard NewReno and CUBIC flows, we show significant performance gains in lightly-multiplexed scenarios, without losing the delay-reduction benefits of deploying AQM. ABE is a sender-side-only modification that can be deployed across networks incrementally (requiring no flag-day) and offers a compelling reason to deploy and enable ECN across the Internet.

Item Type: Conference Paper
Murdoch Affiliation(s): School of Engineering and Information Technology
Item Control Page Item Control Page