scholarly journals Improved RTT Fairness of BBR Congestion Control Algorithm Based on Adaptive Congestion Window

Electronics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 615
Author(s):  
Wansu Pan ◽  
Haibo Tan ◽  
Xiru Li ◽  
Xiaofeng Li
Keyword(s):  
Congestion Control ◽  
Control Algorithm ◽  
Delivery Rate ◽  
Propagation Time ◽  
Network Simulator ◽  
Round Trip ◽  
Congestion Window ◽  
Queuing Delay ◽  
Congestion Control Algorithm ◽  
Tcp Congestion Control

To alleviate the lower performance of Transmission Control Protocol (TCP) congestion control over complex network, especially the high latency and packet loss scenario, Google proposed the Bottleneck Bandwidth and Round-trip propagation time (BBR) congestion control algorithm. In contrast with other TCP congestion control algorithms, BBR adjusted transfer data by maximizing delivery rate and minimizing delay. However, some evaluation experiments have shown that the persistent queues formation and retransmissions in the bottleneck can lead to serious fairness issues between BBR flows with different round-trip times (RTTs). They pointed out that small RTT differences cause unfairness in the throughput of BBR flows and flows with longer RTT can obtain higher bandwidth when competing with the shorter RTT flows. In order to solve this fairness problem, an adaptive congestion window of BBR is proposed, which adjusts the congestion window gain of each BBR flow in network load. The proposed algorithms alleviate the RTT fairness issue by controlling the upper limit of congestion window according to the delivery rate and queue status. In the Network Simulator 3 (NS3) simulation experiment, it shows that the adaptive congestion window of BBR (BBR-ACW) congestion control algorithm improves the fairness by more than 50% and reduces the queuing delay by 54%, compared with that of the original BBR in different buffer sizes.

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

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4128
Author(s):  
Wansu Pan ◽  
Xiaofeng Li ◽  
Haibo Tan ◽  
Jinlin Xu ◽  
Xiru Li
Keyword(s):  
Congestion Control ◽  
Control Algorithm ◽  
Path Model ◽  
Correction Function ◽  
Propagation Time ◽  
Network Simulator ◽  
Gamma Correction ◽  
Round Trip ◽  
Feedback Information ◽  
Congestion Control Algorithm

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.

scholarly journals Performance of TCP CUBIC and TCP BBR on IEEE802.11s Mesh Network

2020 ◽  
pp. 639-645
Author(s):  
Katsuya Atsuta ◽  
◽  
Satoshi Kouya ◽  
Naoshi Sakamoto
Keyword(s):  
Congestion Control ◽  
Bit Error Rate ◽  
Error Rate ◽  
Control Algorithm ◽  
Loss Probability ◽  
Mesh Network ◽  
Propagation Time ◽  
Round Trip ◽  
Communication Performance ◽  
Congestion Control Algorithm

In this study, IEEE802.11s mesh networking was formulated as it expected to be widely used because of its convenience. The properties of IEEE802.11s mesh networking were investigated and the results revealed its faulty communication performance in a multi-hop network. This could be explained based on Mathis’s theory for loss-based TCP congestion control algorithm that suggests that with an increase in delay, the loss probability decreases the communication performance. Recently, Google proposed TCP Bottleneck Bandwidth and Round-trip propagation time (BBR), both of which may tolerate a high bit error rate. This algorithm does not follow Mathis’s model. In this study, we measure the performance of TCP CUBIC and TCP BBR on a mesh network, followed by an evaluation of the properties of this mesh network.

scholarly journals Adaptive Decrease Window for BALIA (ADW-BALIA): Congestion Control Algorithm for Throughput Improvement in Nonshared Bottlenecks

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 294
Author(s):  
Geon-Hwan Kim ◽  
Yeong-Jun Song ◽  
Imtiaz Mahmud ◽  
You-Ze Cho
Keyword(s):  
Congestion Control ◽  
Control Algorithm ◽  
Transmission Control Protocol ◽  
Control Mechanisms ◽  
Congestion Window ◽  
Transmission Control ◽  
Control Protocol ◽  
Congestion Control Algorithm ◽  
Lossy Links ◽  
Single Path

The main design goals of the multipath transmission control protocol (MPTCP) are to improve the throughput and share a common bottleneck link fairly with a single-path transmission control protocol (TCP). The existing MPTCP congestion control algorithms achieve the goal of fairness with single-path TCP flows in a shared bottleneck, but they cannot maximize the throughput in nonshared bottlenecks, where multiple subflows traverse different bottleneck links. This is because the MPTCP is designed not to exceed the throughput of a single-path TCP competing in the bottleneck. Therefore, we believe that MPTCP congestion control should have different congestion window control mechanisms, depending on the bottleneck type. In this paper, we propose an adaptive decrease window (ADW) balanced linked adaptation (BALIA) congestion control algorithm that adaptively adjusts the congestion window decrease in order to achieve better throughput in nonshared bottlenecks while maintaining fairness with the single-path TCP flows in shared bottlenecks. The ADW-BALIA algorithm detects shared and nonshared bottlenecks based on delay fluctuations and it uses different congestion window decrease methods for the two types of bottleneck. When the delay fluctuations of the MPTCP subflows are similar, the ADW-BALIA algorithm behaves the same as the existing BALIA congestion control algorithm. If the delay fluctuations are dissimilar, then the ADW-BALIA algorithm adaptively modulates the congestion window reduction. We implement the ADW-BALIA algorithm in the Linux kernel and perform an emulation experiment that is based on various topologies. ADW-BALIA improves the aggregate MPTCP throughput by 20% in the nonshared bottleneck scenario, while maintaining fairness with the single-path TCP in the shared bottleneck scenario. Even in a triple bottleneck topology, where both types of bottlenecks exist together, the throughput increases significantly. We confirmed that the ADW-BALIA algorithm works stably for different delay paths, in competition with CUBIC flows, and with lossy links.

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