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Fast-ish OpenVPN tunnel

500 Mbps OpenVPN throughput over the Internet, nice. Was aiming for 900 Mbps, which seems to work on LAN, but no cigar. [Edit: --tcp-nodelay --tcp-queue-limit 256 got me to 680 Mbps. Which is very close to non-tunneled line speed as measured by a HTTP download.]

OpenVPN performance is very random too. I seem to be getting different results just because I restarted the client or the server.

The config is two wired machines, each with a 1 Gbps fibre Internet connection. The server is a Xeon E3-1231v3, a 3.4 GHz Haswell Xeon. The client is my laptop with a USB3 GbE adapter and i7-7700HQ. Both machines get 900+ Mbps on Speedtest, so the Internet connections are fine.

My OpenVPN is set to TCP protocol (faster and more reliable than UDP in my testing), and uses AES-256-GCM as the cipher. Both machines are capable of pushing multiple gigaBYTES per second over openssl AES-256, so crypto isn't a bottleneck AFAICT. The tun-mtu is set to 9000, which performs roughly as well as 48000 or 60000, but has smaller packets which seems to be less flaky than big mtus. The mssfix setting is set to 0 and fragment to 0 as well, though fragment shouldn't matter over TCP.

Over iperf3 I get 500 Mbps between the endpoints. With HTTP, roughly that too. Copying from a remote SMB share on another host goes at 30 MB per second, but the remote endpoint can transfer from the file server at 110 MB per second (protip: mount.cifs -o vers=3.0). Thinking about it a bit, I need to test with a second NIC in the VPN box, now VPN traffic might be competing with LAN traffic.

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Built art installations, web sites, graphics libraries, web browsers, mobile apps, desktop apps, media player themes, many nutty prototypes