Very low throughput

[skleeschulte]

Hi there, thanks for creating this project! Unfortunately I get only very low throughput with a Layer 3 site-to-site connection when the SoftEther VPN servers run in Docker containers. "Very low" is 30 to 80 KB/s in both directions (tested with SMB and HTTP download), whereas the slowest links at the two sites are 4 MB/s (= 32 Mbps) and 1.25 MB/s (= 10 Mbps). Pings are ok (20 to 30 ms).

I closesly followed 10.6 Build a LAN-to-LAN VPN (Using L3 IP Routing), except only for two sites. Containers are running in privileged mode.

Here is what I tried to narrow down the problem:

• Installed SoftEther VPN on dedicated Windows machines with the same site-to-site configuration: Here almost the full link speed can be utilized over VPN.
• Ran the "Network Traffic Speed Test Tool" that ships with SoftEther from container to container: Again, almost the full link speed is reached (29.4 Mbps and 8.87 Mbps).
• Inspected containers CPU und RAM usage when transferring over VPN: CPU is around 1% and RAM is around 3%.
• Tested many different settings for the Cascade Connection, all without noteworthy effect: Disabled NAT-T, disabled SSL-Encryption, disabled UDP acceleration, disabled QoS functions, enabled Half-Duplex mode, doubled the number of TCP connections to 16.
• Set the options DisableKernelModeSecureNAT and DisableIpRawModeSecureNAT to 1 for all Virtual Hubs (although SecureNAT is not used): No effect. (That was a hint I found here: https://github.com/siomiz/SoftEtherVPN/issues/55#issuecomment-541154840)
• Checked that the ethernet connections in the containers have promiscuous mode enabled: They do.
• Tried containers based on CentOS (latest), alpine and debian: No differences in VPN speeds.

I also found the hint to modify the MTU settings in SoftEther VPN, but as I understand it, as SecureNAT is disabled this does not apply.

And I also found hints that using tap devices as local links and bridging to eth0 could resolve speed issues (e.g. here: SoftEther VPN has very slow download, while upload is high). Unfortunately I did not manage to set this up in a container.

Any ideas what to do next?

[siomiz]

Thank you for the detailed report!

As you can see this image is really a script wrapper around SoftEther VPN, so I'm assuming there is an underlying network performance issues within the Docker networking layer...

Are you using Docker Desktop for Windows to run the image? There are reported slowness with it and they suggest:

• Use transparent network driver (via https://github.com/docker/for-win/issues/698#issuecomment-310533089)
• Use Docker on Windows Subsystem for Linux (WSL) (via https://github.com/docker/for-win/issues/1936#issuecomment-614532361)

Unfortunately I don't have the environment to test it by myself... Hope this helps!