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Is there a way of increasing the data window sizes in SFTP?

Posted: 03/08/2012 02:17:31
by Nicklas Bergfeldt (Standard support level)
Joined: 12/04/2007
Posts: 19


I have received the following question fr om one of our clients and have not been able to determine if it is possible to change this using the TElSSHServer component.

I have a customer that would like to use SFTP as transfer method over a 50ms RT 1GigE dedicated pipe.

Based on 1MB standard data window sizes in openssh, we are ultimately limited to transfers in the range of 20MB/s (1s / 50ms * 1MB).

We have had luck with using the hpn-ssh patch (http://www.psc.edu/networking/projects/hpn-ssh/) for openssh on linux to linux links wh ere we increase the data window size to 128MB, but our customer would like to access the sftp server using Windows machines.

We have successfully converted the SFTPServer demo into an Indy-based SFTP server (instead of the TServerSocket that's included)...
- But is there a way of changing the standard data window sizes?
- Is that a client side request and the server will simply comply if requested?
- Do you know of a client that can specify this increased data window size?
Posted: 03/08/2012 17:05:28
by Ken Ivanov (Team)

Thank you for contacting us.

Unfortunately, SSH window is not adjustable in TElSSHServer and related components (while it is in client-side components). I have added the corresponding task to the to do list, it will be ready for one of the early SBB 10 builds.



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