Optimizing TCP for high WAN throughput while preserving low latency

What this post added

This post details Cloudflare's efforts to optimize TCP for high WAN throughput while preserving low latency, a critical requirement for newer products like Magic WAN, WARP, Spectrum, and Gateway. It explains the trade-offs between minimizing latency spikes by limiting TCP receive window size and achieving high throughput over high-latency links. The post introduces Linux autotuning as a mechanism to dynamically adjust buffer sizes and receive windows based on RTT and application read rates, and proposes specific sysctl values (net.ipv4.tcp_rmem, net.ipv4.tcp_wmem, net.ipv4.tcp_adv_win_scale) to achieve a balance between throughput and latency for long fat networks and elephant flows.