Should BBR be the default TCP Congestion Control Protocol?

TL;DR

This study evaluates whether BBR should be the default TCP congestion control protocol, demonstrating its superior throughput and performance in diverse network environments, but also highlighting latency trade-offs.

Contribution

The paper provides a comprehensive performance comparison of BBRv2/v3 with traditional TCP variants across multiple network types, emphasizing its potential as a default protocol.

Findings

BBR achieves high throughput across all tested environments.

BBR demonstrates strong fairness and coexistence with other flows.

Latency and jitter trade-offs vary between protocols, affecting suitability.

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.