S-Series PBX works as OpenVPN server. IP phone connects PBX by OpenVPN. The account on IP phone is registered, but sometimes not.
Test the VPN within the same network as the IP phone on a computer. Ping test shows some packets loss, and the latency reaches to 400ms or higher.
Therefore it is network issue rather the PBX issue.
But the user insists to use OpenVPN. How could we make it work?
We could try the Compression option and use TCP protocol to make the network impact minor.
On the server side.
On the client side.