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Large Transfers Abort After XX Minutes Without Completing  -  KB Article #1157

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Those that use Microsoft's "high security Web hosting" template for setting up a more secure IIS Web site may experience problems with large file transfers. Typically the transfers will abort after a number of minutes, even if they are active.

The cause of the problem is a change made by this template to the registry. It sets an idle time-out for TCP connections. The FTP protocol uses two connections to get the work done: There is a command connection for issuing instructions to the server, and each time a data transfer is done this establishes a seperate data connection. During a data transfer the command connection is typically idle, and this means it will get disconnected if the registry's idle time-out is reached. Disconnection of the command connection also disrupts any ongoing data transfer for that session, as dictated in the FTP standard.

The registry key involved is:


The default is not to have the KeepAliveTime key at all, the template adds this. If a time-out is desired make sure the value is sufficiently large to accomodate all file tranfers (the value is in [ms]). Alternatively, an FTP client that periodically sends a command to the server during file transfers will also prevent the command connection from aborting.