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SSH Tunnel Compression

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Access locked and protected files in Windows, read and write disks and partitions and more.
#3512
Posted: 08/01/2007 15:56:14
by Charlie Steaderman (Standard support level)
Joined: 08/01/2007
Posts: 3

I have developed a C# application that uses SSH tunneling to connect to a MS SQL database. In general, the database connection works, but I have been getting complaints that large SQL queries (queries that contain large WHERE clauses) were failing (timing out). I am able to reproduce the problem using the SSH tunnel that my application creates, as well as with the EldoS simple tunnel sample applications as well as with PuTTY. Using compression with PuTTY, though, eliminates the timeout problems. So I tried to enable compression using the TElSSHLocalPortForwarding class (ForceCompression and CompressionLevel) and it appears that there is no compression negotiated (CompressionAlgorithmClientToServer and CompressionAlgorithmServerToClient are both zero after connection event is fired). How do I enable compression using the TElSSHLocalPortForwarding class?

- Charlie
#3513
Posted: 08/02/2007 02:42:31
by Eugene Mayevski (EldoS Corp.)

1) Did you enable ZLib compression algorithm via CompressionAlgorithms property?
2) Are you using the registered or trial version? Trial version has speed limitations that can influence the behaviour as well.


Sincerely yours
Eugene Mayevski
#3521
Posted: 08/03/2007 10:16:47
by Charlie Steaderman (Standard support level)
Joined: 08/01/2007
Posts: 3

Eugene,
The CompressionAlgorithm property is for the SFTPClient class, but I am using the LocalPortForwarding class. LocalPortForwarding only has read-only properties to examine the compression algorithm after the connection is made. Any other ideas?

- Charlie
#3522
Posted: 08/03/2007 10:30:18
by Ken Ivanov (EldoS Corp.)

Quote
LocalPortForwarding only has read-only properties to examine the compression algorithm after the connection is made.

It also contains CompressionAlgorithms property (it should be accessed as set_CompressionAlgorithms() in several .NET languages). Please use it to enable ZLIB compression algorithm.
#3523
Posted: 08/03/2007 10:50:19
by Charlie Steaderman (Standard support level)
Joined: 08/01/2007
Posts: 3

Innokentiy,
Yes, I found the set_CompressionAlgorithms property and called is as
Code
m_sshTunnel.set_CompressionAlgorithms(SBSSHConstants.__Global.SSH_CA_ZLIB, true);
but the object still shows both direction's compression algorithm as 0 when I check in the OnOpen event. Any other thoughts?

- Charlie
#3524
Posted: 08/03/2007 11:10:56
by Ken Ivanov (EldoS Corp.)

Just found out -- some algorithm properties are not adjusted correctly after SSH connection is established (and CompressionAlgorithmClientToServer/CompressionAlgorithmServerToClient are two of them). So most likely compression is actually being used, but the properties are not set to the appropriate algorithm values. We will prepare the fix for the upcoming build update.

BTW, are you still having the original timeout problem (with Zlib algorithm enabled)?
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