Volatile connection speed

okonvicka

I am using OpenVPN to sync data between two remote NAS devices, one from QNAP and the other from Synology. The source (moving FROM) has upload of circa 20 Mbps, the destination has download far above. However, when I upload data from the source to destination (using ftp), I get very volatile speeds - at one point, it is at peak around 10 Mbps, ten seconds later it goes down to 5 and around and around.

Both NASes have CPU utilization around 20%, so my guess that this could be caused by too compelx encryption seems to be invalid. Do you have any advice what I could do to stabilize the speed somewhat?

openvpn_inc

Hi o,

I'd suggest testing outside the tunnel. That is, (for ipv4 assuming neither device has an "external" IP address) do a DNAT / port forward from the router to one device, have it listen using iperf3, then have the other device connect to that and push a measured amount of data.

I'd try also with iperf3 inside the tunnel, because that reduces the chance of quirks in software (not to mention the quirky old FTP protocol itself.)

I doubt openvpn is the cause, but one occasional possibility we see is if you're running it (using AES) on a CPU which lacks the AES-NI instruction set. In Linux / /proc/cpuinfo terms that would be the "aes" flag.

regards, rob0