Saturating 10 Gigabit on Linux

Wringing full speed out of a network used to be a niche pursuit, the stuff of 10G home labs and datacenter transfers. That’s changing fast. Multi-gig fiber is landing in homes everywhere, even Hawaiian Telecom is selling 3 Gig out here on the Big Island. A fast link is no longer just the wire between your own machines; it’s the wire to the internet too. And Linux still ships network defaults sized for a slower era, so on a fast link, especially a long one, they leave throughput unused. Here’s the sysctl set I run, what each knob does and where it actually matters, and the single-stream iperf3 result over 20 feet of in-wall Cat 5e: 9.75 Gbit/s.