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Help with conclusion of observed openVPN performance.

Posted: Mon Aug 05, 2019 10:20 am
by tobiasbp
Hello forum. 1st time poster here....

I have been playing around with openVPN. I have set up an openVPN server. I can connect from a remote location (The client) and access resources on the servers network(s) just fine. So, functionality is working the way I want.

However, I see a wide range of performance when transferring through the VPN. I'm using iPerf for my tests.

The server is on a 200/200Mbps connection. When connection the client directly through the firewall in front op the server's network(s), I get around 250/250Mbps (Internet is not involved). That's fast enough for me. At that point, it looks to me like I'm, bound by the CPU on the openVPN server.

When connecting from different homes, I get very varying results. The best result is when the client is on a 100/100Mbps fiber connection. I can get close to the 100Mpbs both ways. All the other locations I have tried to connect from, have much worse results. I'm not close to getting a transfer rate matching the client's line. Usually I get something like 50Mpbs on 100Mpbs lines. Often, I can see the transfer starting out at something close to line speed, and then drop, and vary quite dramatically.

I have looked at the results from, and the tests show results matching the official line speeds, on the lines where I get poor results when using openVPN.

I have tried using both TCP & UDP with openVPN. I'm using port 443 as to not be identified på the ISP as openVPN-traffic (And be able to connect out from networks with limits on outbound ports). I don't see much of a change.

Based on my observations, I suspect all the "bad" lines to the throttled by their ISPs. What do other experienced openVPN users think? Is throttling likely based on my observations? What should/could I do from here to try to get better throughput with openVPN? Should I ask my users to get better ISPs? Any suggestions and thoughts much appreciated.