OpenVPN proxy performance problems

  • I'm having issues with my OpenVPN proxy setup, it's working fine when browsering etc but as soon as I start downloading something bigger there is an issue.

    Speedwise I can actually get pretty good when measuring against different speed check services but with larger files there seems to become some congestion, often after about 100MB that lower my download from say 3-5MB/sec to just a few hundred kB before dropping out.
    If I limit the connection to say 1MB/sec it keeps fairly steady at between 600kB - 1MB/sec and doesn't cut out, my pfsense is running on an Intel Atom 1,6Ghz but it never goes above 45%, openvpn never over 35% and also minor downloads does not suffer this problem.

    I got a few ideas what it might be but any help in how to check these would great;

    • 1. OpenVPN Encrypt/Decrypt timings are a little to slow building up a que that when maxed makes the connection choke on it as well as results in too many lost packages that doesn't fit in the que and connection breaks on a timeout?

    • 2. I'm running pfSense in a "multi-cpu" setting because of Intel Atoms "semi-support-hyper threading"  and this might in some way because it's not really a dual core hinder pfSense form handling it optimal?

    • 3. There is a buffer somewhere in pfSense that I can't find that for some reason maxes out at around 100MB and can't handle the traffic? (this seems unlikely and weird but still)

    any idea how I can see where the problem occurs?

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