My OpenWRT box is connected to a cellular modem via Ethernet on the WAN port, and the LAN port feeds my APs and wired hosts. All Internet traffic is going through a WireGuard VPN, as described in this guide.
With the VPN enabled, I can get 20-30 Mbps on speedtest.net. However, when one of my devices decides to download software updates or anything of that nature, my other devices struggle to load webpages. This led me to set up SQM as described here. The selected interface is the VPN interface, download speed is set to 12,288 Kbps and upload is 512 Kbps. Link Layer Adaptation is set to Ethernet and I'm not quite sure what the overhead should be. Should it be 44 for Ethernet, 80 for typical WireGuard overhead, or 80+44=124 for both Ethernet and WireGuard? I've been trying out each of these but can't say I've noticed much difference between them.
With SQM enabled, speedtest.net struggles to get more than 7Mbps. It often stays below 6Mbps. This is the case with each of the overhead values I've tried. One trend I have noticed is that the speeds increase near the end of the test. Is this simply the nature of SQM?
Trying not to obsess over getting good speedtest results, but it is frustrating to see it go down so much. Any input would be appreciated. Thanks!