Level3 had an interesting blog post on this a while back: http://blog.level3.com/open-internet/observations-internet-m...

Basically certain ISPs refuse to increase connection capacity with backbone providers like level3. Instead they (Comcast) is trying to get Netflix to connect directly with them and charge them a premium in doing so.

They refuse to increase settlement free capacity. Level 3 can pay for the bit-miles beyond what they are carrying in return for the ISPs, or Netflix can do what every other company does and lease lines as needed.

Level 3 is never going to pay someone else for capacity, they are a tier 1. Their entire business model is "being big enough to never have to pay someone else for capacity".

Do you have any links to articles or discussions that talk about this? I'd like to understand it more.

Maybe you just take another route to your VPN gateway than to Netflix. So Netflix may be saturated, when your VPN is not.

Without VPN, the traceroute shows a direct connection to the destination. It's quite literally the next hop on the network.

   7  hu-0-10-0-1-pe04.56marietta.ga.ibone.comcast.net (68.86.83.182)  22.233 ms  11.978 ms  10.577 ms
   8  a104-72-128-31.deploy.static.akamaitechnologies.com (104.72.128.31)  11.783 ms  11.075 ms  18.287 ms

With VPN, it's Comcast -> Corp -> ATT -> Netflix/Akamai. That's a rather longer route.

Doesn't matter. What will be full in 99% of the cases will be the Comcast connection to $content_provider. In many cases an entire metro area will have no spare capacity between any of the major backbone providers and Comcast, so there is almost nothing you can do if you do not have the capability to route that traffic to a different region. This is why many times you will see "scenic routes" when on Comcast - it's providers routing traffic around Comcast's regional congestion in many cases.

While this happens with many providers, Comcast is about the worst offender. They are quite happy to allow peering links to remain full at peak indefinitely - it's a way to put pressure on the content networks to pay for access to their routes over a private peering session. If you're a major web hosting operation, your customers will demand great performance to Comcast. They don't really care that Comcast is strong-arming paid peering agreements via those demands. It's especially awesome because Comcast generally charges more for bits to their tiny portion of the Internet, than what you pay for bits to a major backbone for the full table.

Unfortunately you can't prove whether the decreased throughput is due to throttling or simply congested routes.