SparkLabs Forum

Since I am new to OpenVPN I have a simple performance question. I setup iperf to test performance of the firewall with and without running through OpenVPN. I have a Windows 7 system on the Wan side of the router and a Windows 10 system on the lan side of the router. Running iperf without the VPN I get approx 600Mb/s throughput. Running through the OpenVPN tunnel I am maxing out at 90Mb/s. Is this a OpenVPN limitation per client? Or is there some way to increase the bandwidth per client?

Hi s4rs,

There's a lot of factors that go into your tunnels performance. By far and away the largest factor is the relation between the encryption you are using and the processing power of both the client and server. If you are using a strong cipher, you will lose network performance as each packet takes longer to encrypt at the client end, then decrypt at the server end.

Other more minor factors are things like your servers ability to route each packet, as an extra layer of NAT and firewall rules comes into play as well for example.

Regards,
Eric

The processor runs at appox 32% so there is head room. Not sure if there is a driver limitation or some other bottleneck. Seems strange it caps 100Mb/s. I would expect some slowdown but not a factor of 4x slower. I tested this on an Intel Quad Core N3150 Processor system with 8G of ram. I just picked up an Intel Core i5 3317U system with 8G of ram and see if that makes a difference. I will be surprised if it does.

Hi s4rs,

The following may help - https://community.openvpn.net/openvpn/w ... orks_Linux

Regards,
Eric

Eric,
Thanks for the link. I tested those configurations and I saw a reduction in throughput. I think the issue is I am using Windows instead of Linux for the client. I am not sure if the tunnel MTU of 6K works. If I do a ifconfig on the firewall I see the change to 6K, if I look at Windows it 1.5K and you can't set it higher. I think the performance dropped due to fragmentation but would have to run a trace to verify..

Its good to know this.