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I have a strange problem and I'm at a loss to solve it. I've been tweaking at the settings for a while but nothing seems to improve. I have tried servers from all over the world and even moved to the non-standard ports. I did find moving to a non-standard port gave a bit of an average boost so I was more able to sustain up near the 10M max rate continuously than before. I assume this is just because most clients are connected to 443/udp and there's the OpenVPN single thread issue on the server.


I am on a 24/1 ADSL2 connection with ~180ms latency to the closest LA servers. I can get slightly better latency into Singapore, but I'd rather terminate in the USA since most of my traffic ends up there anyway.


What I see is that I cannot exceed about 10Mbps.


I started out assuming it was just because my desktop OS is shit and its TCP window handling was slowing me down. I used DownloadThemAll to open dozens of connections instead of single-streaming a download. That didn't help. I was still capped at 10MBPS.


I didn't see heavy CPU usage in my router but I ruled it by terminating the VPN on my high end i7 machine (with AES-NI) and repeating the DownloadThemAll test. It didn't help. The same test off the VPN saturates my link at 24MBPS.


I have a few questions...


First, is anyone else using OpenVPN in a similar situation (24/1 and ~200ms latency)? Do you see acceptable performance?


Second, are there any tweaks to the config that might help improve the situation? I've tried forcing the sndbuf/rcvbuf settings to 512k but found that they hinder more than help.


Third, I see what looks like high uplink utilization while pulling at the 10M rate over the VPN. the 1M uplink is actually quite saturated. I don't see similar when I disable the VPN. Is this normal for openvpn? If that's the case then I'm stuffed until I can increase my uplink rate. I didn't think OpenVPN added this much overhead though.


There's nothing else I can think of to work out what's going on. Any suggestions?

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my suggestion is to use the link there and set up a test that mimics a VPN connection.  if you see options for running the test encrypted, do it.  go into the settings for the test, select just one server near the VPN server.  See what speed you get with that test.  I suspect that you won't see (much) above 10mbit/s.

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