Modest BBR: Enabling Better Fairness for BBR Congestion Control

Zhang, Yuxiang; Cui, Lin; Tso, Fung Po

doi:10.1109/iscc.2018.8538521

Cited by 28 publications

(11 citation statements)

References 12 publications

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“…Because BBR is a work in progress, many issues [5]- [9] were reported for the initial BBR v1 announced by Google. One of the serious issues is throughput imbalance due to the RTT differences of BBR flows.…”

Section: Thus New Congestion Control Algorithms Based On Variousmentioning

confidence: 99%

“…Sasaki et al [17] Miyazawa et al [18] examined fairness between CUBIC and BBR and found extreme inter-protocol throughput imbalances and periodic throughput variations when coexisting with CUBIC. Zhang et al [9] proposed Modest BBR to mitigate the aggressiveness of BBR when the bottleneck buffer is small. BBR was modified to be sensitive to packet loss, reducing the sending rate based on loss so the CUBIC flow could use the proper bandwidth.…”

Section: Related Workmentioning

confidence: 99%

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Delay-Aware BBR Congestion Control Algorithm for RTT Fairness Improvement

Kim

Cho

2020

IEEE Access

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In late 2016, Google proposed the Bottleneck Bandwidth and Round-trip propagation time (BBR) congestion control algorithm to achieve high bandwidth and low latency for Internet traffic. Unlike loss-based congestion control algorithms, BBR works without filling the bottleneck buffer. Consequently, BBR can reduce packet loss and minimize end-to-end packet delay, which has attracted the attention of many researchers in recent years. However, some studies have reported the creation of persistent queues that cause unintended problems, resulting in a serious fairness issue between TCP BBR flows with different round-trip times (RTTs). Although existing congestion control algorithms also exhibit fairness issue between different RTT flows, BBR has a more serious problem in that the imbalance is considerable even with small RTT difference between the two flows, and the long RTT flow uses most of the bandwidth. The preponderance of long RTT flows is a serious problem because a particular user may cause imbalance by maliciously increasing the delay. Therefore, we propose a Delay-Aware BBR (DA-BBR) congestion control algorithm to mitigate the RTT fairness issue between BBR flows. In a network emulation experiment using the Mininet, the DA-BBR increased the fairness index by 1.6 times that of the original BBR, and the retransmission was greatly reduced. DA-BBR flow with short RTT demonstrated fair throughput even in competition with DA-BBR flows where RTT is five times higher.INDEX TERMS BBR, congestion control, fairness, round-trip time, TCP.

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Section: Thus New Congestion Control Algorithms Based On Variousmentioning

confidence: 99%

Section: Related Workmentioning

confidence: 99%

Delay-Aware BBR Congestion Control Algorithm for RTT Fairness Improvement

Kim

Cho

2020

IEEE Access

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“…Recently, the extensive research has been conducted to further improve the performance of BBR [24][25][26][27][28][29][30]. Moreover, Google has been actively working on developing BBR v2, an improved version of the current BBR v1 [31].…”

Section: A Brief Overview Of Bbrmentioning

confidence: 99%

Coupled Multipath BBR (C-MPBBR): A Efficient Congestion Control Algorithm for Multipath TCP

et al. 2020

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Multipath transmission control protocol (MPTCP) is a promising transport layer protocol that enables a device to utilize multiple communication interfaces simultaneously, thereby achieving high throughput. A congestion control algorithm (CCA) employed in MPTCP constitutes a key part that controls the data flow through different subflows (SFs). There are two fundamental challenges associated with MPTCP CCAs. First, MPTCP flows should have an advantage over single-path flows; second, MPTCP flows should be fair, indicating that SFs sharing a common bottleneck should occupy a capacity fairly close to that required by a single-path flow. Several MPTCP CCAs have been developed; however, they have failed to satisfy these challenges in all scenarios. Recently, Google has introduced the bottleneck bandwidth and round-trip-time (BBR), a new CCA for single-path TCP, achieving high throughput with minimum delay by employing a network model. In the present paper, we propose a novel MPTCP CCA based on BBR named coupled multipath BBR (C-MPBBR) that satisfies the fundamental challenges by exploiting the concept of network modeling in BBR. C-MPBBR addresses the first challenge by closing the lowbandwidth SFs by tracking the delivery rate and bottleneck bandwidth (BtlBW). Then, it satisfies the second challenge through identifying those SFs that share a common bottleneck and dividing the BtlBW share corresponding to a SF among them. We implemented C-MPBBR in the Linux kernel, tested it on a wide range of scenarios by the Mininet emulation experiments, and the real-world Internet, and confirmed that the proposed C-MPBBR outperforms the existing MPTCP CCAs in terms of successfully satisfying the fundamental challenges by ensuring both throughput and fairness.

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“…Because BBR is still in the development stage, fairness between BBR algorithm and other loss-based CCAs [ 26 , 27 , 28 , 29 ] and RTT fairness [ 12 , 30 , 31 , 32 , 33 , 34 ] need to be improved. In the above analysis, one of the most serious problems of BBR is the RTT fairness problem in the protocol.…”

Section: Introductionmentioning

confidence: 99%

Improvement of RTT Fairness Problem in BBR Congestion Control Algorithm by Gamma Correction

Pan

Tan

et al. 2021

Sensors

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Google proposed the bottleneck bandwidth and round-trip propagation time (BBR), which is a new congestion control algorithm. BBR creates a network path model by measuring the available bottleneck bandwidth and the minimum round-trip time (RTT) to maximize delivery rate and minimize latency. However, some studies have shown that there are serious RTT fairness problems in the BBR algorithm. The flow with longer RTT will consume more bandwidth and the flows with shorter RTT will be severely squeezed or even starved to death. Moreover, these studies pointed out that even small RTT differences will lead to the throughput of BBR flows being unfair. In order to solve the problem of RTT fairness, an improved algorithm BBR-gamma correction (BBR-GC) is proposed. BBR-GC algorithm takes RTT as feedback information, and then uses the gamma correction function to fit the adaptive pacing gain. This approach can make different RTT flows compete for bandwidth more fairly, thus alleviating the RTT fairness issue. The simulation results of Network Simulator 3 (NS3) show that that BBR-GC algorithm cannot only ensure the channel utilization, but also alleviate the RTT fairness problem of BBR flow in different periods. Through the BBR-GC algorithm, RTT fairness is improved by 50% and the retransmission rate is reduced by more than 26%, compared with that of the original BBR in different buffer sizes.

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Modest BBR: Enabling Better Fairness for BBR Congestion Control

Cited by 28 publications

References 12 publications

Delay-Aware BBR Congestion Control Algorithm for RTT Fairness Improvement

Delay-Aware BBR Congestion Control Algorithm for RTT Fairness Improvement

Coupled Multipath BBR (C-MPBBR): A Efficient Congestion Control Algorithm for Multipath TCP

Improvement of RTT Fairness Problem in BBR Congestion Control Algorithm by Gamma Correction

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