One of the effects of using a VPN is that your traffic goes over a longer path than before, which means more interconnect bandwidth usage than before. An oversaturated interconnect doesn't explain this well. What a VPN does that explains the improvement better is hide the fact that your traffic is going to Netflix from your ISP, meaning that they no longer know to slow down their traffic. The fact that the VPN speeds things up is evidence that the problem is the last link and is deliberate.TronPaul wrote:It does surprise me a bit that VPNs would improve service. That does prove that the issue is not on the last link (from the ISP to you), which would be the case if they oversold bandwidth to the area, but that the interconnect is over saturated (like Level 3 has reported). I bet an investigation of different VPNs, using different interconnects might yeild interesting results.
Now, a VPN could also help if the new path happened to bypass a congested interlink, but if that was the case using one would be hit-or-miss as to whether it improved things. The new path might go over the same interlink or pick one even more congested. If using a VPN restores performance with a high probability, then the case against the ISP is quite strong.