Virgin Media - Slow via Windows client, but not Linux...

FrJackHackett

Virgin Media customer here. It's been well reported that VM seem to throttle VPN connections. I would've only gotten around 30Mbps on Windows using the PIA client. However, I recently made the switch to Linux (specifically, Ubuntu 17.10) and have been using the PIA client there with no speed issues. I get around 135Mbps, which is what I get even when not connected. Router is a few metres away, so this is the speed I would expect. Just wondering if there are any differences in the clients between Windows and Linux, or is this more likely to do with differences in network implementation on Linux compared to Windows?

At least now I can recommend a solution to people in a similar position... switch to Linux! 

TheLynx1

I use Virgin Media and same issues - HUGE throttle

I use port 443 TCP , it helps but not 100%

[Deleted User]

@FrJackHackett, this definitely sounds like you might be encountering the TAP bottleneck on Windows! This typically happens between 100-250mbps rather than 30, but the fact that your speeds are so much faster on Linux makes me think that this is probably the case. In short, there are two ways OpenVPN can transmit traffic:

The TAP is essentially analogous to plugging in your computer straight to our servers with an Ethernet cable. The TAP is a layer 2 (data link) device, which your computer sees as virtual network card . OpenVPN bridges your real network card to the virtual TAP network card, meaning that your LAN and the remote network (in this case, PIA) functionally become one. Typically TAP devices are only used if access to the LAN is necessary, but Windows requires that virtual network cards send Ethernet frames rather than IP packets, which is why Windows uses a TAP. Unfortunately, the OpenVPN TAP driver for Windows is very inefficient (likely due to a high number of context switches, according to this report on github). We've discovered that the previous NDIS 5 implementation of the TAP driver tends to be faster and more stable, but, at this time, speeds on Windows simply can't approach those on Linux. 

The VPN tunnel is implemented completely differently on Linux, which uses a TUN device, a layer 3 (IP) based method of VPN implementation. The TUN only transports IP packets, and also only tunnels VPN traffic. That means that there's less overhead overall since TUN devices only transmit traffic destined for the VPN client. OpenVPN was also initially developed on Linux, and its developers still primarily focus on that platform.

That's why speeds on Linux tend to be so much better than Windows!

FrJackHackett

@PIAColleen, thanks for the excellent explanation. Would go some way to explaining why PPTP or L2TP connections on Windows don't see the same speed drops. I don't plan on moving back to Windows, so it's not going to be an issue for me in future, but good to know why it's happening nonetheless. 

@TheLynx1, I've tried port 443 as well, but it made no difference. There's a video of someone on YouTube demonstrating the throttling with AirVPN and being able to get full speed by using SSL 443. I trialled AirVPN to see if that might solve the issue, but it didn't. 

Looks like Linux is the fix!

TheLynx1

So what is the solution I still have this issue - I don't want to use linux

@PIAColleen please advise I have same issue