[Bloat] BBR talk from Stony Brook University

Rich Brown richb.hanover at gmail.com
Sat Dec 12 13:11:54 EST 2020

Google Alerts for "bufferbloat" pointed to this talk at Stony Brook University in New York State:

Dates:  Thursday, December 17, 2020 - 12:30pm to 2:00pm (US EST: UTC-5)
Location:  Zoom - contact events at cs.stonybrook.edu for Zoom info.

Abstract: BBR is a new congestion control algorithm and is seeing increased adoption especially for video traffic. BBR solves the bufferbloat problem in legacy loss-based congestion control algorithms where application performance drops considerably when router buffers are deep. BBR regulates traffic such that router queues don’t build up to avoid the bufferbloat problem while still maintaining high throughput. Though BBR is able to combat bufferbloat for sustained steady traffic such as large file downloads, our analysis shows that video applications experience significantly poor performance when using BBR under deep buffers. In fact, we find that video traffic sees inflated latencies because of long queues at the router, ultimately degrading video performance.

In this talk, I will present our work on the interaction between BBR and streaming video. We investigate the relationship between network metrics such as delay and delivery rate during the video run and the quality of subsequent video segments. However, we find only weak correlations, suggesting that another factor is at play. Our empirical investigation reveals that BBR under deep buffers and high network burstiness severely overestimates available bandwidth and is slower to converge to steady state, both of which result in BBR sending substantially more data into the network, causing a queue buildup. This elevated packet sending rate under BBR is ultimately caused by the router’s ability to absorb bursts in traffic, which destabilizes BBR’s bandwidth estimation and overrides BBR’s expected logic for exiting the startup phase.

Original Notice: https://www.cs.stonybrook.edu/Rebecca-Drucker-Research-Proficiency-Presentation-Investigating-BBR-Bufferbloat-Problem-DASH-Video

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