[varenc]

I'm sure others know waaay more about this, but I think it's a thing you can improve locally. Though usually I think of it as the other way around, where maxing out upload severely impacts download. My understanding is that this causes bufferbloat[0], making packets queue up for a long time on your gateway, ultimately limiting you to way less bandwidth then you should be able to get.

My one experience with this is on Ubiquiti hardware where there's a feature called "Smart Queues" you can enable. Really it's FQ_CODEL[1] under the hood. If you tell it your real maximum up/down bandwidth, minus ~5%, it'll enforce those limits in a way that prevents buffer bloat and lets you use nearly your full download bandwidth even when your upload bandwidth is maxed out. On Ubiquiti gear this has a CPU impact since it has move some traffic handling from dedicated hardware to the CPU. But it was a huge night and day difference for me. After enabling this, having a couple people on Zoom calls (highish upload) no longer tanked everyone else's download speed.

Also I think this stuff matters more when you have a large multi-user network. For normal home life, definitely not worth it. (In my case it was wifi for ~20 people).

[0] https://en.wikipedia.org/wiki/Bufferbloat [1] https://en.wikipedia.org/wiki/CoDel