Improving Latency with Active Queue Management (AQM) During COVID-19

TL;DR

This paper analyzes the impact of Active Queue Management (AQM) on latency in home networks during COVID-19, showing that AQM significantly reduces latency under load, improving user experience.

Contribution

It provides a large-scale comparative analysis of cable modems with and without AQM, demonstrating its effectiveness in reducing latency during high network load.

Findings

AQM reduces upstream latency from ~250ms to 15-30ms.

Large-scale data supports accelerated deployment of AQM.

Significant improvement in user experience with AQM.

Abstract

During the COVID-19 pandemic the Comcast network performed well in response to unprecedented changes in Internet usage and video communications applications that are sensitive to network latency have exploded in popularity. However, in today's typical networks-such as a home network-those applications often degrade if they are sharing a network link with other network traffic. This is a problem caused by a network design flaw often described using the term 'buffer bloat'. Several years ago, Comcast helped to fund research and development in the technical community into new Active Queue Management (AQM) techniques to eliminate this issue and AQM was later built into Data Over Cable Service Interface Specification (DOCSIS) standards. Just prior to the pandemic, Comcast also deployed a large-scale network performance measurement system that included a latency under load test. In addition, Comcast happened to deploy two otherwise identical cable modems; one with upstream AQM enabled, and the other without. This fortuitous confluence of events has enabled Comcast to perform a comparative analysis of the differences between cable modem gateways using AQM with those that lack that enhancement, at a unique level of scale across many months of time and millions of devices. The data reveals significantly better upstream latency under load performance when AQM is used. For the device with AQM, most of the latency under load tests resulted in 15-30 milliseconds of latency. In comparison, the device without AQM averaged roughly 250 milliseconds of latency, between 8-16 times higher, a highly significant difference to the end user quality of experience. These large-scale measurement comparisons should provide additional data to justify accelerated deployment of AQM in DOCSIS and other Internet Service Provider networks and user-purchased home network equipment.