There was a similar discussion on HN a few weeks ago regarding a similar issue about ISPs buffering the CDN (I think).

I dug up a link that I saved:

http://mitchribar.com/2013/02/time-warner-cable-sucks-for-yo...

Here is the fix:

  sudo ipfw add reject src-ip 173.194.55.0/24 in
  sudo ipfw add reject src-ip 206.111.0.0/16 in