Debugging my new network, when 10 Gigabit Ethernet Runs at 300 Megabits

When I was struggling to figure out why so many of my devices on my gigabit network were only getting 100 megabits, I learned that a lot more of my devices were on 10/100 ethernet than I expected. Including some recent purchases (TV's especially).

It took me a while because I assumed gigabit had been kind for far longer than it actually was in practice.

> had its receive buffers at the default 512, although it supported up to 4096. I increased them. I love an increased buffer.

Dave Täht is rolling in his grave

Might also want to see: https://docs.pixeldrain.com/posts/2024-03-07_network_optimiz...

Is there a similar diagnostic that can be run on a Playstation 5? I generally have good download speeds on my network but it seems to take forever to install games on my PS5.

Another example: PCIe ASPM exit latency. Fast LAN speed (because the card does not have time to go into sleep) but low internet speed (manages to enter ASPM if the host is at least 3ms away)

https://lore.kernel.org/intel-wired-lan/803760bf-04ff-4b23-8...

Awesome writeup, thanks. I wasn't aware of iperf3 as a tool. This helped me confirm that the 10GbE lines I ran a while ago are in good shape.

I didn't need to change any NIC settings, but I'm on an X540 instead of an E610-XT2

Recently I found my bilateral Bandwidth was limited from the switch to host. Turns out I didn’t plug the sfp+ all the way in. Amazing it worked at all

good old buffer packet size

anyone old enough from dialup modems and RS232 to remember the trick of replacing the 16450 UART with 16550 if you were lucky enough to have it on a socket instead of soldered?

that took it from a 1-byte buffer to 16-bytes, instant speed boost

same idea going from X-modem to Y-modem for transfers, 128bytes vs 1024bytes before checksum

surprised ethernet by now doesn't constantly try to negotiate larger buffer windows

I upgraded my entire home network to 10GBase-T earlier this year, and I get 10Gbps speeds everywhere, but I run Linux everywhere, except for a few Windows VMs, which also get 10Gbps. I think the TLDR for this article comes down to "Windows networking sucks", which everybody should already know anyway.