BBR2
also: BBRv2, tcp_bbr2
BBR2 is the second generation of Google's Bottleneck Bandwidth and Round-trip time (BBR) congestion control algorithm for TCP, designed to improve network performance and fairness over high-speed, high-latency connections.
BBR2 is an advanced TCP congestion control algorithm that replaces the traditional loss-based approach with a model-based strategy. Instead of waiting for packet loss to detect congestion, BBR2 measures the bottleneck bandwidth and round-trip time to proactively adjust sending rates, making it especially effective for modern networks with large bandwidth-delay products.
The original BBR algorithm improved performance on long-distance, high-bandwidth links, but BBR2 refines this further with better fairness between competing flows and improved behavior on Wi-Fi and satellite networks. It adapts to network conditions more gracefully and reduces unnecessary latency spikes.
BBR2 can be enabled in Linux kernels 5.18+ via sysctl net.ipv4.tcp_congestion_control=bbr. Network administrators and cloud providers use BBR2 to optimize throughput on intercontinental connections and heavily loaded data center networks.