So, this is probably a good time to couch my observations with a few qualifications:
- My analysis wasn't particularly rigorous, and I didn't even save my data (other than in the blog post). If I had know how much attention this would get, I would have done a lot more test runs of more sites from more locations (and I may as a follow-up).
- It's entirely possible that I'm misinterpreting what I saw. In particular, there may be some cwnd caching going on somewhere a la RFC-2140. However, since Google mentions that they don't believe cwnd caching is effective in their presentation on IW10, I think that's unlikely in the www.google.com case. It does, however, seem like a plausible explanation for the www.microsoft.com behavior.
- A number of commenters have taken issue with my invocation of network neutrality. They make a good point. This isn't a net neutrality issue, strictly speaking. It is (arguably) an issue of network fairness, however.