I'm getting this error on my OpenVPN connection to AirVPN, I'm running PfSensePlus 23.05, the speeds I get are about 5% of line speed. If I connect with my laptop's openVPN client to AirVPN over my ISP it's fast, no issue.

I rolled back to 5.2.5 and my speeds were about 95% of line speed, however, when I inspected the logs the same error came up!

The openVPN client is configured with UDP over port 443, 80 and 2018, Mode: Peer to Peer ( SSL/TLS ), Data Ciphers: AES-256-GCM, Digest: SHA512.

If I switch over to TCP I get about 50% of line speed.

I've seen this error posted elsewhere but I've not seen a good explanation of what the cause is.

Any ideas of how to resolve this and hence what the cause is ?