This is all about peering.
First, you can see what it takes to be a full peer with Comcast here: http://www.comcast.com/peering.
Every entity on the internet has to pay somebody for their bandwidth (assuming the traffic is transiting outside of that entity’s network). If two parties are exchanging similar amounts of data, then they will normally enter into a settlement-free relationship (no money is exchanged). If the traffic is unbalanced, then money is exchanged.
Netflix buys bandwidth in lots of different ways. Previously, they were sending data to Comcast mostly via Cogent. Because the agreement Comcast and Cogent had didn’t cover the massive imbalance, Comcast throttled all Cogent traffic (of which Netflix was the biggest percentage by far). Netflix wanted to put one of their servers in the Comcast NOC to avoid this problem, but Comcast wouldn’t go for it. Instead, Netflix entered a peering arrangement with Comcast directly (ie not via a third party like Cogent). This benefits Comcast because the traffic imbalance is being paid for and benefits Netflix because they are paying Comcast less than they had to pay Cogent.
If Comcast had been targeting Netflix, then they would have also slowed down Netflix streams coming from other (Level 3) backbones, but they didn’t. If a Comcast customer watched Netflix on an AppleTV, it worked beautifully.
This is better for Comcast, better for Netflix, and better for Netflix customers. The loser is Cogent.
