Optimizing HTTP/2 prioritization with BBR and tcp_notsent_lowat

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Getting the best end-user performance from HTTP/2 requires good support for resource prioritization. While most web servers support HTTP/2 prioritization, getting it to work well all the way to the browser requires a fair bit of coordination across the networking stack. This article will expose some of the interactions between the web server, Operating System and network and how to tune a server to optimize performance for end users.


On Linux 4.9 kernels and later, enable BBR congestion control and set tcp_notsent_lowat to 16KB for HTTP/2 prioritization to work reliably. This can be done in /etc/sysctl.conf:

net.core.default_qdisc = fq net.ipv4.tcp_congestion_control = bbr net.ipv4.tcp_notsent_lowat = 16384 Browsers and Request Prioritization

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Read full article » https://blog.cloudflare.com/http-2-prioritization-with-nginx/

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