Engineers often face slow data transfer speeds between geographically distributed data centers, even when VPN tunnels are established. A common scenario involves transferring 50 GB backups within an hour, where high latency and packet loss hinder performance. The default Linux TCP congestion control algorithm, CUBIC, often fails to fully utilize available bandwidth in such conditions.
Google introduced the BBR algorithm in 2016 to address these limitations. Unlike CUBIC, which interprets packet loss as congestion, BBR estimates the maximum bandwidth and round-trip time of the network bottleneck. It optimizes the amount of data in flight to saturate the channel without creating unnecessary queues, which can significantly improve throughput for long-distance TCP connections.
BBR is not a universal solution for network issues like misconfigured MTU, overloaded VPN gateways, or slow hardware. It must be enabled on the specific server acting as the data sender to be effective. Administrators can check for availability using sysctl and apply the configuration by setting net.ipv4.tcp_congestion_control to bbr.
Performance testing should be conducted using tools like iperf3 with both single and multiple streams to measure real-world impact. In practical scenarios, enabling BBR has resulted in speed increases of up to 6 times, though results vary by network. For further technical exploration, the author recommends investigating the updated BBRv3 implementation.
