Low throughput for sFTP over high latency high bandwith network

Our client (that uses ssh.net) runs on AWS and the sftp server is hosted on Prem, and our uploads are multi-threaded.
We use the default UploadFile() method, which through various tests seem to perform the best on this network.

We however are seeing that the performance is way below par when compared to the sftp command from openssh for a single thread.
Like 3 times slower.
And with multiple threads, it goes crazy slow, to the point that the total throughput from all the threads are lower than that it gets from a single thread.

OpenSSH's sftp command on the other hand scales quite well.

Open SSH has a patch called HPN-SSH for such networks, not sure if something can be inspired from that.

Comienza con la ruta predeterminada UploadFile() del cliente SFTP y perfila una única carga a través de una red de alta latencia; después compárala con el comportamiento de OpenSSH sftp descrito en el issue. Reproduce el caso con varios hilos y mide si el rendimiento agregado disminuye al añadir hilos; se considera terminado cuando se haya identificado la causa y se haya mejorado el rendimiento o documentado la limitación.