I'm trying to transfer a set of large files internationally using SFTP, but I am finding my international partner can't get upload speeds above ~50k despite very good connections on either side. We can get multiple connections uploading at this speed (so not bandwidth?), but no single upload improves in speed, which is a problem as many files are several gb in size.
The SFTP is being hosted using the standard Apple OSX "Remote Login" SFTP system.
Is there a way to improve upload speeds, or is there a different SFTP host that would help? It's not clear to me if this is a configuration problem or an inherent limitation of the protocol.
(For security reasons I need to be using an end-to-end encrypted peer-to-peer connection -- no cloud services).