Timeouts with SFTP

Hello,

 

I'd be grateful for any advise regarding the following issue.

 

We have a pair of BIG-IP appliances (10.2.2 Build 763.3 Final) configured with one VS (serving 21/tcp and 22/tcp connections).

 

There are no issues whatsoever with FTP, however with SFTP, users occasionally get timeouts while uploading/downloading files. It happens quite rarely to random users connecting from different locations. The only common thing I managed to identify from SFTP logs was 120 seconds between upload/download attempt and the time out. Here is how it looks like from the logs:

 

[2014-07-14 10:01:01]: SYSTEM [ 2346] - [userx] Upload started for file 'D:\ROOT\userx\20140714-x987bs78.zip'

 

[2014-07-14 10:03:01]:CONNECT [ 55325] - Connection timed out - Shutting down connection...

 

[2014-07-14 10:03:02]:CONNECT [ 55325] - Connection terminated

 

Could it be somehow related to the idle timout in SFTP VS configuration? As far as I understood with FTP, even if there is no data transfer, the connection is kept alive via control ports, which is not the case for SFTP. Therefore if there is no data transfer within x seconds the SFTP connection is terminated, but I couldn't find anything in the BIG-IP config that mentions 120 seconds...

 

Any hints would be greatly appreciated.

 

Thank you.