PRB: Files Only Partially Downloaded over ISA Server When You Delay the Download (317981)

SYMPTOMS

If you download a large file by using Internet Security and Acceleration (ISA) Server 2000 and you delay the download on the client computer (that is, you wait before you save or open the file) for more than two minutes, only a part of the file is downloaded.

CAUSE

ISA Server uses a timeout value when it resets an idle connection to a remote server. By default, this value is 120 seconds for incoming and outgoing Web requests.

When the client pauses the download on the internal site, the connection on the external site (that is, the external network interface of ISA Server that is connected to the Web server) is idle. Because of the default timeout value of 120 seconds, ISA Server resets the connection when no traffic exists on the external connection for more than 120 seconds. When the client then resumes the download, the external connection is not reestablished, and the client only receives the part of the file that is already downloaded.

RESOLUTION

You can change the default timeout value of 120 seconds to a higher value until it meets your requirements. To do this, follow these steps:

Right-click the ISA Server computer or array name, and then click Properties.
Under Outgoing Web Requests, click Configure.
Change the connection timeout value to a higher value (note that this value is expressed in seconds).
When ISA Server prompts you to restart the Web Proxy service, do not restart the Web Proxy service.
Restart the ISA Server Control service. To locate the ISA Server Control service, locate Administrative Tools, and then locate Services.

MORE INFORMATION

When you change the connection timeout value, remember that security issues such as "Denial of Service" attacks can result. Microsoft recommends that you keep the timeout value as low as possible.