My network transmission rate seems much slower than it should be. My desktop runs Stretch (v9, oldstable) on a Pentium 4 (3 GHz) with 4GB of RAM (the maximum) and a 1Gbps network interface card (NIC). We pay for fiber optic service at 500Mbps. The specifications for my router (ZyXEL VMG4381-B10A) say 100/45 Mbps (but more on that below). Without much else running, speedtest.net shows rates of just 54/58 Mbps (download/upload). In all cases I have a hardwired RJ45 connection between the NIC and the router. It's no better if I make a direct connection from the fiber optic cable to the NIC, bypassing the router.
Meanwhile my wife's Windows 10 laptop, plugged into the router, gets 542/137 Mbps at speedtest.net. Her laptop has a 2.4-GHz quad core processor, 16GB of RAM, and (like my desktop) a 1Gbps NIC. As an aside, I don't understand why her rate isn't limited by the router to 100Mbps. Ethtool reports that I have a speed of 1000Mb/s, Full Duplex, and Auto-negotiation on. I'll admit that I don't understand all of the configuration options on the router. My wife's laptop shows that the service and the router can do 500Mbps with a 1Gbps NIC. The obvious difference between her laptop and my desktop is the RAM (16GB vs. 4GB). Is that the end of the story, or is there some way I can get my desktop to do much better? Thanks.