mBBR - Improving BBR Performance Over Rate-Limited Mobile Networks

In spite of the advances in mobile networks, most mobile data plans impose a fixed monthly data quota, beyond which the attainable bandwidth is explicitly limited to a much lower data rate. This rate-limited behavior could degrade TCP performances significantly, as confirmed by a major service provi...

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Bibliographic Details
Main Authors: Zhu, Shengtong, Liu, Yan, Guo, Lingfeng, Ngan, Rudolf K. H., Lee, Jack Y. B.
Format: Conference Proceeding
Language:English
Subjects:
Bandwidth
BBR
congestion control
Correlation
Costs
Cubic
Limiting
mobile network
Packet loss
Production
Protocols
rate-limited network
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Summary:In spite of the advances in mobile networks, most mobile data plans impose a fixed monthly data quota, beyond which the attainable bandwidth is explicitly limited to a much lower data rate. This rate-limited behavior could degrade TCP performances significantly, as confirmed by a major service provider who observed strong correlation between high packet loss rate and mobile rate limiting. The high packet loss translates directly into increased bandwidth cost which is significant in a large-scale service. This work investigates this problem in two steps. First, we establish the link between the high loss rate observed and mobile network rate limiting through experiments in both controlled testbed and production mobile networks. The results revealed that packet loss can and does increase dramatically in rate-limited mobile networks. This affects both TCP Cubic and BBR, the two most widely deployed TCP implementations. BBR, in particular, was impacted far more significantly, resulting in packet loss rates exceeding 40% in some cases. Second, we analyzed BBR's operations under rate limiting to uncover the causes and developed new mechanisms - mBBR, to improve its performance. Experimental results show that mBBR can reduce BBR's packet loss rate by up to 88%, thereby saving substantial bandwidth costs incurred in retransmitting lost packets when the user is under rate limiting.
ISSN:2643-3303
DOI:10.1109/ICNP59255.2023.10355605