OpenVPN fast-io and sndbuf/rcvbuf options in the GUI

  • Rebel Alliance Developer Netgate

    I went ahead and added fast-io and buffer options to the OpenVPN server and client GUI for 2.4 since we have seen several reports that they significantly help speeds, especially on SG-1000. They will both be in snapshots built after the time of this post, so most likely late today / early tomorrow.

    The options default to off, so if you have the options in advanced settings already then you are still safe to upgrade. Remove them from the custom options box and then set them in the GUI instead.

    fast-io will only work on UDP connections (client or server) and for clients it also cannot work if you have "Limit outgoing bandwidth" set. It also does not work on Windows, so don't expect it to help out there. The server side can have it enabled, but we do not offer a push option for it, and it won't be in the export package.

    The Send/Receive buffer setting isn't quite so clear. Reports on the forum and elsewhere usually show a value of 512KiB. This may be a good starting point, but you might also want to try higher or lower values in case they perform better for a specific site.

    Where possible, you probably will want to set both ends of a connection to have similar settings for fast-io and buffer sizes.

    Ticket is here:

  • Thanks!

    At the moment I am happy with:

    sndbuf 393216;
    rcvbuf 393216;
    push "sndbuf 393216";
    push "rcvbuf 393216";

    With your modifications, do we also have the option to push (last two lines) those settings to the client?

  • Rebel Alliance Developer Netgate

    Not at this time, you could still keep the push lines if you want.

    Since the optimal buffer size could vary based on operating system and remote client location/circuit type/latency/etc I don't see pushing the same value to all clients as something we'd want to encourage.

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