In my experience higher latency due to bufferbloat occurs when my internet connection is saturated, like the example in the article of downloading a game.
However, people can still have latency issues from their ISP even if their connection isn't fully saturated at home. Bufferbloat is just one situation in which higher latency is created.
Yes, my Zoom call was terrible BECAUSE I was also downloading Diablo saturating my connection. But my Zoom call could also be terrible without anything else being downloaded if my ISP is bad or any number of other things.
As someone who worked in a large ISP, if a customer says their bandwidth is terrible but they are getting their line saturated most ISPs will test for latency issues.
Bufferbloat is one of many many reasons why someone's network might be causing them high latency.
The really horrible bufferfloat usually happens when the upload bandwidth is saturated -- upload bandwidth tends to be lower so it'll cause more latency for the same buffer size.
I used to have issues with my cable modem, where occasionally the upload bandwidth would drop to ~100kbit/s (from normally 5Mbit/s), and if this tiny upload bandwidth was fully used, latency would jump from the normal 20ms to 5500ms. My ISP's customer support (Vodafone Germany) refused to understand the issue and only wanted to upsell me on a plan with more bandwidth. In the end I relented and accepted their upgrade offer because it also came with a new cable modem, which fixed the issue. (back then ISPs didn't allow users to bring their own cable modem -- nowdays German law requires them to allow this)
It is true that there is an interplay between bandwidth utilization and latency.
However (assuming no prioritisation), if your bandwidth is at least double your video conference bandwidth requirements then a download shouldn’t significantly affect the video conference since TCP tends to be fair between streams.
Even when I was on a 10Mb/s line I found gaming and voice was generally fine even with a download.
However, if you’re using peer to peer (like BitTorrent), then that is utilizing dozens or hundreds of individual TCP streams and then your video conference bandwidth getting equal amount per all other streams is too slow.
Bufferbloat exacerbates high utilisation symptoms because it confounds the TCP algorithms which struggle to find the correct equalibrium due to “erratic” feedback on if you’re transmitting too much.
It’s like queuing in person at a government office and not being able to see past a door or corner how bad the queue really is, if you could see it’s bad you might come back later, but because you can’t you stand a while on the queue only to realize quite a bit later you’ll have to wait much longer than you initially expected, but if you’d known upfront it would be bad you might have opted to come back later when it’s more quiet. Most people feel that since they’ve sunk the time already they may as well wait as long as it takes, further keeping the queue long.
Higher throughput would help, but just knowing ahead that now’s a bad time would help a lot too.
I do wish most consumer ISPs supported deprioritising packets of my choice, which would allow you to download things heavily at low priority and your video call would be fine.
However, people can still have latency issues from their ISP even if their connection isn't fully saturated at home. Bufferbloat is just one situation in which higher latency is created.
Yes, my Zoom call was terrible BECAUSE I was also downloading Diablo saturating my connection. But my Zoom call could also be terrible without anything else being downloaded if my ISP is bad or any number of other things.
As someone who worked in a large ISP, if a customer says their bandwidth is terrible but they are getting their line saturated most ISPs will test for latency issues.
Bufferbloat is one of many many reasons why someone's network might be causing them high latency.