Client-side VPN causing bufferbloat

I'm connected to a VPN at all times via a Windows PC and it always creates bufferbloat for all clients connected to the router whenever something is being downloaded. I think it's related to the VPN encryption but I'm not sure. The issue manifests with or without OpenWRT, with or without SQM and its various scripts, as well as when using a different router. The only reason I'm asking about it here is that I'm currently stuck with OpenWRT, so it's the only way to potentially address the issue. Connecting the whole network to the VPN is not an option.

A vpn encapsulates all traffic into what fq_codel would see as a single flow, thus only the AQM portion would be working. However, if you set your download speed for SQM correctly, at say 85% of the measured speed, only the vpn connection should bloat even the slightest, and everything else be fine.

Thanks. I have a 100 Mbps connection and so I had the ingress speed set to 80000 or 85000. I didn't want to go too low, knowing that it limits the maximum download speed at all times.

However, I followed your advice and lowered it even further to 72000 to adjust based on the actual speed of about 85 Mbps at best, which seems to have significantly minimized the bloat.

The solution is not ideal, as it means I'm never going to be downloading at anything near 100 Mbps even if there are no other clients connected and the ISP is offering as much as advertised, but it's tolerable for now.

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