A repeatable Linux network baseline
Small sysctl changes that are easy to understand and verify.
This note documents a practical approach used in Steppe Infrastructure Notes. The goal is a setup that can be explained, reproduced, and checked from outside the machine.
Change a short list deliberately
BBR, fq, TCP Fast Open, and MTU probing are useful only when the kernel supports them and the workload benefits. Keep settings in one documented file instead of scattering commands across shell history.
sysctl net.ipv4.tcp_congestion_control
sysctl net.ipv4.tcp_fastopenWatch the effective queue
A congestion-control algorithm does not replace a suitable qdisc. Check that fq is active on the real interface and compare latency under load before and after a change. Throughput alone hides bufferbloat.
tc qdisc show dev eth0Persist and re-check
Runtime values can disappear after a reboot. Apply the persistent configuration, restart the host during a maintenance window, and read the values back before marking the work complete.
sysctl --system
uname -r