Can an ISP throttle a VPN?

[Oogs]

So i recently got a subscription to nordvpn and from day 1 its been giving this issue that whenever the vpn is connected the speed wont go above 25mbps. I have a 100mbps plan. This is happening for all devices on my network;phones, PC's, laptops everything. I've been going back and forth with customer care trying different troubleshooting and diagnosis steps with no luck so far. Since its happening on all my devices i thought it must be an issue with my router or ISP. Using a manual OpenVPN profile for NordVPN works relatively fine and gives around 70mbps down/up speeds but they are UDP and TCP VPNs and are a little inconsistent when it comes to speed and latency. Note that changing to OpenVPN inside the NordVPN apllication does not work, it only works when connected through the OpenVPN GUI application. I want to use the VPN over their NordLynx protocol which is based on the WireGuard VPN tunnel.

 

Any help is appreciated attaching speedtests and the diagnostic data generated through the NordVPN application.

DiagnosticsLog.txt 2022-04-12 20_36_14Z-logs.zip

[PDifolco]

Mmm, could be badly setup (too small) packet size

 

Check and adjust if needed as below :

 

 

[Alex Atkin UK]

1 hour ago, Oogs said:

Using a manual OpenVPN profile for NordVPN works relatively fine and gives around 70mbps down/up speeds but they are UDP and TCP VPNs and are a little inconsistent when it comes to speed and latency.

I'm confused, are you using TCP or UDP when it works well?  You can't be using both at the same time.

 

If your ISP has high contention/congestion/packet loss, then TCP will likely work better than UDP, which would explain the difference.  Its also likely TCP would have a higher priority, especially if you use port 443 and they don't inspect the packets to see what they are so would treat it as normal https traffic.

Despite claims of Wireguard being more resistant to congestion and latency, I've found it more flaky than OpenVPN even using UDP.

 

The benefit Wireguard has on unstable connections is it doesn't drop the connection as it has no concept of connections, but that is also why it can be unstable as it will keep using a server that is suffering packet loss whereas OpenVPN would drop and when you reconnect you'd likely be using a different server.

[Oogs]

18 hours ago, PDifolco said:

Mmm, could be badly setup (too small) packet size

 

Check and adjust if needed as below :

 

 

Yes I have tried this. In my case the MTU was 1392, so the computers MTU was set to 1420 (1392+28) but it did not solve the issue

 

[Oogs]

18 hours ago, Alex Atkin UK said:

I'm confused, are you using TCP or UDP when it works well?  You can't be using both at the same time.

 

If your ISP has high contention/congestion/packet loss, then TCP will likely work better than UDP, which would explain the difference.  Its also likely TCP would have a higher priority, especially if you use port 443 and they don't inspect the packets to see what they are so would treat it as normal https traffic.

Despite claims of Wireguard being more resistant to congestion and latency, I've found it more flaky than OpenVPN even using UDP.

 

The benefit Wireguard has on unstable connections is it doesn't drop the connection as it has no concept of connections, but that is also why it can be unstable as it will keep using a server that is suffering packet loss whereas OpenVPN would drop and when you reconnect you'd likely be using a different server.

Ok, so in the NordVPN application you can set the VPN protocol to either NordLynx, OpenVPN TCP or OpenVPN UDP, using any of these the download speed gets limited to 25mbps. Now if i forget about the NordVPN application completely and download the OpenVPN application from openvpn.net and add a connection using a config file which is available on the NordVPN website it works much better and i get a download speed of around 70mbps when connecting with either of the protocols TCP or UDP.

 

I really wanted to get wireguard to work because I'm using it mostly for gaming and streaming and the network dropouts are a problem. The reason i have to use the VPN is because last year there were some issues with the submarine fibre cables that connected India to EU servers (I'm form India) and the latency has been horrible 300-350ms when it used to be 100-120ms earlier. Using a VPN bypasses that issue somehow, probably because the routing is different and you get around the same ping as you would normally +-10ms.