IIS FTP service – download timeouts and restarts getting the data twice


We have an IIS FTP site on a Windows Server 2003 x64 machine.

Application Layer Gateway service is disabled (so http://support.microsoft.com/kb/931130 does not apply). Windows Firewall service is disabled as well. Connection timeout for the FTP site (there is only one) is set to 1,200 seconds = 20 minutes.

An external client can connect to the site, list directory contents and download small files. When a client attempts to download a large file (eg, if the download continues for 3 minutes, which is still under 20 minutes, but relatively long), the server sends all data, then the connection times out, the client issues REST / RETR commands attempting to restart the download since after the last byte (which I believe should succeed and receive exactly 0 bytes), and the server behaves as if the client tried to restart after byte 0, that is, it sends the entire file all over.

Any ideas on how to fix this?

Best Answer

Try downloading the file from the server itself and then try downloading the file from the same network as the server. If it works on the server then you may have a network issue, if it works from the network then you may have a firewall or router issue.