Microsoft KB Archive/232512

= TCP/IP May Retransmit Packets Prematurely =

Article ID: 232512

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Standard Edition

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This article was previously published under Q232512



SYMPTOMS
When transmitting data over high-delay networks (for example, satellite links), transfer throughput may be lower than expected and the number of packets retransmitted may be unnecessarily high.



CAUSE
This problem occurs because TCP uses a retransmit timer to retransmit packets that do not appear to have reached the receiver. To set this timer, TCP uses information about the historical Round Trip Time (RTT) for each connection, which it measures by observing the time between sending packets and receiving acknowledgments for them.

The Microsoft Windows NT 4.0 TCP/IP stack incorrectly computes the retransmit timer because of a math error. When transmitting packets over high-delay networks, this can result in unnecessary retransmissions and lower throughput.



Windows NT Server or Workstation 4.0
To 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:


 * http://www.microsoft.com/windows/servicepacks/ -or-


 * 152734 how to obtain the latest windows nt 4.0 service pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/directory/overview.asp

Windows NT Server 4.0, Terminal Server Edition
To 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:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack



STATUS
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT Server version 4.0, Terminal Server Edition Service Pack 6.



MORE INFORMATION
The TCP retransmission count can be observed using the Performance Monitor utility or using the "netstat -s" command.

For additional information about this issue as it pertains to Microsoft Windows 95/98, please see the following article in the Microsoft Knowledge Base:

236926 Windows 95/98 TCP/IP May Retransmit Packets Prematurely

Additional query words: premature

Keywords: kbhotfixserver kbqfe kbbug kbfix kbqfe KB232512

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