Very Slow Throughput with WinSCP via sftp/scp

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level20peon
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Very Slow Throughput with WinSCP via sftp/scp

There are noticable differences between SCP and SFTP transfers but ranging below 10% they are not my real problem. Encryption also is not a problem, as Computers used in my setup are very fast machines. (There was no noticable difference between encryption turned on or off)


Tested with:

-Transfering large files
-Client to Server Transfer, using following Clients


-OpenSSH scp/sftp 4.9p1 (Cygwin installation) ~ 17.7 MB/s
-Tunnelier 4.31 ~ 10.1 MB/s
-Filezilla 3.3.1 ~ 8.4 MB/s
-pscp/psftp 0.60 ~ 8.3 MB/s
-WinSCP 4.26 ~ 6.2 MB/s


-OpenSSH scp/sftp 4.9p1 (on Linuxbox) ~ 17.7 MB/s
-pscp/psftp 0.60 (on Linuxbox) ~ 12.6 MB/s


As you can see the OpenSSH clients are three times faster than WinSCP on my LAN. Funny thing is that the difference is even greater when I am using the same software over a DSL connection. I am getting ~ 600 KB/s using OpenSSH scp/sftp clients while getting only 120 KB/s using WinSCP.


I captured the transfers using Wireshark. There are visible differences between WinSCP and OpenSSH clients. While OpenSSH transfers MOSTLY packets of 1452 bytes length, WinSCP sends packets of 84 bytes length inbetween EVERY 1452 byte. Looks like loads of overhead to me but I don't know if this is the source of the problem at all.

What could I test or provide in order to find the source for this behaviour ?

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martin
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Re: Very Slow Throughput with WinSCP via sftp/scp

Can you do the same test with PuTTY?
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Martin Prikryl

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level20peon
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I don't know exactly what you are referring to.

I tested pscp/psftp which are the command line versions of Putty (aren't they ?).

They also show the 84 byte packets if this is what you wanted to know.

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martin
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Thanks. That's what I wanted to know.
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