Hi,
Slowness can be caused by a number of issues. It could be a problem with the user’s internet connection, it could be a problem with the user’s router, or it could be caused by software installed on the user’s machine. It could also be a problem with the OpenVPN server, but it sounds like you may have ruled that out if it’s working for other users. Viscosity on Windows 11 should run at full performance without any problem.
I first recommend checking what other software is on the user’s computer. Many security tools, in particular antivirus and security software will attempt to intercept network traffic (as part of filtering or security checking) which can often cause poor performance. In particular, many of these tools often come with VPN services, and may be tunnelling traffic through a third party provider, which will also cause performance problems. If this is a new computer, it often comes with “bloatware” that may be doing this without the user’s knowledge. You’ll want to find out what other software the user is running and try temporarily uninstalling it to see whether the slowness persists.
Routers can also be a source of VPN slowness if configured incorrectly (or if they are having issues). If possible try and bypass the router (such as having the user tether their computer to their phone) and see if the slowness persists.
MTU issues can also cause slowness, or access to resources timing out. Normally if the MTU is set too large for the user’s internet connection their router/modem/computer should fragment the packets, however if MTU path discovery is broken for the user’s connection (for example they have firewalled out ICMP packets) then this may not be happening, which can cause packet loss. This typically results in symptoms like extreme slowness, and access to web pages and resources timing out. If you suspect a MTU issue, try lowering the MTU for the VPN connection to something fairly safe (1380 is a common value) and see if the slowness persists.
Most ISPs will not attempt to filter or throttle VPN traffic, but some do. If you suspect this could be the case, you can try using a different port number, switching protocol, or have the user try connecting to a different OpenVPN server, and see whether the same slowness exists.
Finally, also keep in mind that while some users may have a fast internet connection, they could be attempting to use it over a flaky wifi connection. In particular, if they’re using a new computer by an old wireless AP, there could be compatibility issues at play. I recommend having the user plug their computer in via a network cable as a test as well.
Regards,
Aaron
