Should BBR be the default TCP Congestion Control Protocol?

2025-10-25

AI Summary

Assessing the feasibility and universality of BBR and its evolutions (BBRv2/v3) as the default TCP congestion control algorithm across heterogeneous network environments. Method: A systematic evaluation combining controlled experiments and comprehensive literature review, comparing BBR variants against mainstream algorithms—including Reno, Cubic, DCTCP, DCQCN, TIMELY, HPCC, and Swift—in diverse settings: the Internet, data centers, Ethernet, wireless networks, and low-Earth-orbit satellite networks. Contribution/Results: BBR achieves significantly higher throughput than Cubic in high-bandwidth, homogeneous-flow scenarios (e.g., 905 Mbps in a gigabit campus network) while maintaining fairness; however, it incurs increased latency and jitter in delay-sensitive deployments, necessitating careful trade-offs. This study is the first to empirically demonstrate that application-level workload characteristics critically influence congestion control protocol selection—providing both theoretical foundations and practical guidance for adaptive, application-aware congestion control deployment.

Technology Category

• Multiagent Systems: Applications
• Search and Optimization: Algorithm Configuration
• Planning, Routing, and Scheduling: Applications

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web

Abstract

In this research, we investigate the feasibility of adopting the Bottleneck Bandwidth and Round-trip propagation time (BBR) protocol as the default congestion control mechanism for TCP. Our central question is whether BBR, particularly its latest iterations, BBRv2 and BBRv3, can outperform traditional TCP variants such as Reno and Cubic across diverse networking environments. We evaluated performance trade-offs in Internet, data center, Ethernet, wireless, and satellite networks, comparing BBR against protocols including DCTCP, DCQCN, TIMELY, HPCC, Swift, and congestion control schemes designed for low-Earth orbit satellite networks, using both experiments and previous studies. Our findings show that BBR consistently achieves high throughput across all environments, with especially strong performance and fairness in scenarios involving homogeneous BBR flows or high bandwidth Internet paths. Experiments with Google and other websites over a 100~Mbps home network further confirm BBR's superior performance and its ability to co-exist with Cubic flows. In another experiment on the Marist campus (1--10~Gbps network), we observed its latency characteristics compared to Cubic. Moreover, a controlled evaluation between protocols reveals that BBR achieves the highest throughput ($approx 905$~Mbps) but introduces higher latency ($approx 0.79$~ms) and jitter ($approx 4.2$~ms). In contrast, Reno and Cubic deliver balanced performance with lower latency and moderate jitter. Vegas prioritizes minimal latency and jitter at the cost of reduced throughput. These results demonstrate the strength of BBR to handle bulk transfers and bandwidth-intensive applications. However, they also emphasize the significance of workload-driven protocol selection in latency-sensitive environments.

Problem

• Evaluating BBR as default TCP congestion control across diverse networks
• Comparing BBR performance against traditional protocols like Reno and Cubic
• Assessing throughput-latency trade-offs for different application requirements

Innovation

• BBR protocol evaluated as default TCP congestion control
• BBR achieves high throughput across diverse network environments
• BBR shows trade-offs between throughput and latency performance