It doesn't have to be traffic shaping, it can be something as simple as limited peering capacity. Hanlon's Razor applies, this isn't necessarily malicious cappi

It doesn't have to be traffic shaping, it can be something as simple as limited peering capacity. Hanlon's Razor applies, this isn't necessarily malicious capping. Most ISPs don't have one fat pipe to this magical "internet" place, they have multiple pipes going different places and not all of them are even listed in peeringdb, so their route to a particular CDN might be over private peering which is limited in size (e.g. 1-10Gb). Sure, then excess traffic might go over public peering but that might also then get saturated, or the ISP might force traffic over the private peering to keep the public peering clear for general traffic. If you use a VPN then the traffic will come from a different route and different peering, thus be subject to the capacity of that route. What the OP probably wants is for Zen to have better peering with Akamai (they already have some announced routes).