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Blocking those is making my computer connect to youtube in a way not predicted by my ISP, avoiding the throttling issue. I can now watch videos above 360p with no interruptions!

Jeff! What's actually happening here? My ISP will wise-up and throttle my new alternate youtube sever address, right?

IIRC What has actually happened is you have blocked the primary (and presumably overloaded) youtube servers, so the load balancing automatically punts you to the backup servers. Which will remain fast until more people start doing the same thing.

No I think what's happening is he is blocking his ISP's youtube caching server. Most of the bigger ISPs have them. They store popular videos on them so that they dont get bandwidth sapped when half of their customer base goes online to watch the latest stupid viral video in 1080p. And its his ISP's caching server that is responsible for the throttling, either intentionally, or by idiotic design. My money is on the former.

Now that he's blocked their caching servers, he is defaulting back to youtube itself, which actually sends at a decent speed, because it is not throttled.

Theres a good article or something somewhere that explains it better than I could.

The whois command ($ whois 173.194.55.0) says that Google Inc owns the 173.194.0.0/16 CIDR block whereas apparently XO Communications owns 206.111.0.0/16. Do you know if both of your iptables rules are necessary to see a speedup?

Do you know (e.g., via wireshark) if you were downloading from anyone in those CIDR blocks before, and, if so, which one?

I ran wireshark and got overloaded with information. I might have been listening to the whole network. I might be in trouble with the school network admin.

I'll have to read the wireshark manual and get back to you.

You can filter on, e.g.,

ip.src == 173.194.55.0/24

to see if anything is coming from that block.

It appears that I'm not using the blocked ip, as youtube connects to 74.125.0.25 The filter didn't return any hits at all on either of those IPs. However, I did notice a speed change on the day I made the original post. A large and very noticeable one. Is it possible something changed between now and the 25th? This whole idea came from reddit, so hundreds of thousands of users were probably doing the exact same thing. If the people at google didn't like what was happening to their Youtube, they could have easily changed server IPs.

It's also worth noting that, since I made this post, I've switched operating systems, to Lubuntu 12.10. So when I ran wireshark there's no chance I was still blocking those IPs.

I suppose it's also possible that if there were a load balancing problem (some servers getting too much traffic, some not enough) that they fixed it. All we can do is speculate at this point.

As always, thanks a lot for your assistance. I've learned a lot from you on this forum.