At around 7 Pacific tonight, YouTube was fine. Watched Netflix on an AppleTV for a while, played perfectly at 1080p. Opened computer back up and YouTube was buffering again. Captured the screenshots below.
It seems really clear that something is going on with using AT&T as an egress point that is very specific to YouTube. I've reproduced it enough at my end to feel pretty comfortable saying that. Video is basically unwatchable at 720p when using the FTTN data path from AT&T to YouTube, but directing it out via Sonic works fine even though I'm pumping the whole thing over an OpenVPN connection that's being managed by a $125 router.
What was really interesting is that the video quality improved quite a bit after I'd played through it a couple of times via the AT&T outbound connection. Ring any bells, infrastructure people?
Despite my earlier carping about them, I am beginning to wonder if AT&T is trying to cache YouTube on its end and for whatever reason, that caching isn't working well under load. I can totally see them wanting to drop cache points in at any number of points within their network, and if they're fine under lighter load...
Cause for this could be relatively benign, and as mundane as slow storage on a cache device somewhere.
Anyhow, here are the screenshots. Video was here:
https://www.youtube.com/watch?v=YbBU06irWT8
Before turning VPN on:
Turned VPN on at router, same video same hardware, new browser tab:
Turned VPN off at the router, played the video again on same hardware, new browser tab:
