I used to have trouble doing connection intensive stuff like fetching servers in games or using my browser for other things while thats happening. With a VPN those problems are gone. Why?
Most likely due to peering. Your ISP probably has a good connection to the datacenter that is housing the VPN server you’re connecting to.
But their peering to further away things may not be so great. When you’re using your VPN you no longer have to worry about the peering agreements your ISP has with anyone other than your VPN server.
Usually datacenters have great peering because that is where everyone wants to host their stuff and you certainly won’t pay for a datacenter that has poor quality connectivity.
I’ve encountered this myself with my own ISP and VPN where I actually sometimes get lower pings in games with my VPN active than with it off.
Your ISP cannot do packet shaping when you’re using a VPN.
There are a few reasons why that can happen. Depends on your ISP & VPN services and how they build their networks. There are a few reasons I think might be more common than others.
DNS. Quality DNS actually has a fair bit to do with latency and quickly fetching IP addresses. Your ISP might have had slow DNS servers, or been overloaded.
Routing/peering. The server location your VPN is on may have faster routes to the destinations you go to. The datacenters good VPN’s are housed in usually have mainline ISP’s. Commercial datacenters are usually have fewer hops to backbones than home ISP’s do. Home ISP’s often have network designs that can bottleneck at certain points.
That is yet another reason to use a VPN – better performance (which can happen).
Maybe your ISP believes in doing everything as cheaply as possible, meaning they don’t care about quality.
And your VPN company actually cares – they are well connected to the internet.
I’ve also seen something like that, and my impression was that the ISP throttles the traffic on certain ports/protocols/services but when on VPN they have no clue what you are doing.