Article ID: 223450 - View products that this article applies to.
This article was previously published under Q223450
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/256986/EN-US/ )Description of the Microsoft Windows Registry
When you establish TCP connections between computers across high-delay networks, connection requests and data may be retransmitted unnecessarily. This can result in extra congestion and slow response.
The initial TCP retransmission timer was hard-coded to three seconds.
Windows NT Server or Workstation 4.0To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
A new registry parameter has been added to TCP to allow the initial retransmission timer to be adjusted. This parameter may be useful for high-delay networks, where the round-trip time often exceeds three seconds.
This parameter controls the retransmission time-out of the initial TCP connection request (SYN) and of the first data sent on a connection. It is a global value, which applies to all interfaces in the computer.
To adjust the InitialRtt parameter, perform the following steps:
Windows NT Server 4.0, Terminal Server EditionTo resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/152734/EN-US/ )How to Obtain the Latest Windows NT 4.0 Service Pack
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows NT Server version 4.0, Terminal Server Edition Service Pack 6.
Care should be used when adjusting this value. Setting it to large values will dramatically increase the amount of time that it takes for a TCP connection attempt to fail, if the target IP address does not exist.
For instance, the default value is 3,000, or 3 seconds. By default, a connection request is retried 2 times. The total time-out is (3+6+12) seconds, or 21 seconds.
If this registry value is set to 6,000 (6 seconds), the total timeout will be (6+12+24) seconds, or 42 seconds. During this time, an application can appear to stop responding (hang).
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