internet connection delay

[darkoshi]

For about the last month, I've had an internet issue where the initial "connecting to [whatever URL]" step randomly takes a long time. Randomly as in not always, and not always the same sites. When I try to make it happen, it doesn't happen. The delay isn't always the same length. But it happens many times a day. Once past that initial delay, the page then loads quickly.

It has happened both at Qiao's house and my house; he's got a different ISP than me.
It has happened both on my personal laptop and work laptop, though I think I only noticed it a few times on the work laptop. Most of the time, the work laptop is connected to a VPN; it may have only happened when I wasn't on the VPN, but I'm not sure.
It has happened in various browsers (Waterfox, Firefox, not sure about the others)
Speedtest.net results show nothing unusual.

Do any of you know what could cause this or how to fix it?

Based on what I read on this page, I already tried turning off DNS over HTTPS but that did not fix the problem, so I re-enabled it:
https://www.reddit.com/r/waterfox/comments/qoc9ty/every_new_website_i_visit_in_a_new_session_takes/

... Found another post which might be related to my problem:
https://www.reddit.com/r/waterfox/comments/r76qg8/httpsgoogleapiscom_weird_slow_connection_issue/

Comments

[mellowtigger]

I think DNS is the right suspect. The only other thing I can think of is to disable ipv6 on whatever network device you're using for internet. Especially where vpn is concerned, I've seen continuing problems where both are enabled. The wifi and wired ethernet ports are 2 different network devices on the same computer, and so is the pseudo-device used with the vpn. You could potentially disable ipv6 on all 3 devices on your machine.
https://answers.uillinois.edu/uis/page.php?id=99981 (assuming you're on Windows)

Technical aside:
With vpn, I've also seen a different problem with "collision" in ipv4 addresses, due to the home user's internet service provider using a local internet address that happens to also be used by your employer in their corporate network (behind the their vpn), leading to some communications just disappearing into a rabbit hole of undeliverable packets. There's nothing easy to be done about that problem. Either the employer or the isp has to use different "local" ip addresses, or the whole world needs to switch to ipv6.

[darkoshi]

Thank you. I will test disabling ipv6 to see if that makes a difference.
If it doesn't, maybe I'll try pointing to a different DNS server.