Windows NT Clients Run Out of Ports

This article was previously published under Q149532
This article has been archived. It is offered "as is" and will no longer be updated.
IMPORTANT: This article contains information about editing the registry.Before you edit the registry, make sure you understand how to restore it ifa problem occurs. For information on how to do this, view the "Restoringthe Registry" online Help topic in Regedit.exe or the "Restoring a RegistryKey" online Help topic in Regedt32.exe.

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:
256986 Description of the Microsoft Windows Registry
SYMPTOMS
An Event ID 2009 "Number of sessions exceeds 2048" may be recorded in theevent log and/or clients may be unable to create new connections to theserver.
CAUSE
This behavior can occur because computers that run Microsoft Windows NT clients and use excessive numbers of ports (more than 3,976 simultaneously) may run out of ports before TCP/IP releases closed connections. The TCP/IP-state computer dictates that when a connection isclosed, the connection is not released until two maximum segment lives(MSLs) have passed. This state is defined as the Time-wait state. Since one MSL is defined as 120 seconds, it takes four minutes for a closedconnection to be released in TCP/IP.

NOTE: For more information on MSL and Time-wait, please refer to Internet RFC 793.
WORKAROUND
To resolve this behavior, you must make the following registry change:

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.

HKEY_LOCAL_MACHINE\System\CurrectControlSet\services\Tcpip\Parameters
The registry value is:

TcpTimedWaitDelay

Key: Tcpip\Parameters
Value Type: REG_DWORD - Time in seconds
Valid Range: 30-300 (decimal)
Default: 0xF0 (240 decimal)

STATUS
Microsoft has confirmed this to be a problem in Microsoft Windows NTWorkstation version 3.51 and Microsoft Windows NT Server version 3.51. Thisproblem was corrected in the latest U.S. Service Pack for Windows NTWorkstation or Server version 3.51. For information on obtaining thisupdate, query "servpack" (without the quotation marks) in the Microsoft Knowledge Base.

MORE INFORMATION
For additional information about configuration options for Windows NT 4.0, click the article number below to view the article in the Microsoft Knowledge Base:
170359 How to Modify TCP/IP Maximum Retransmission Timeout

This registry entry was first added in Windows NT 3.51 Service Pack 5. Customers using Windows NT 3.51 need to apply Service Pack 5 before making this modification.
kbnetwork kbbug3.51 NTSrvWkst nttcp
Properties

Article ID: 149532 - Last Review: 12/04/2015 14:30:44 - Revision: 1.1

Microsoft Windows NT Workstation 3.51, Microsoft Windows NT Workstation 4.0 Developer Edition, Microsoft Windows NT Server 3.51, Microsoft Windows NT Server 4.0 Standard Edition, Microsoft Windows NT Server 3.51, Microsoft Windows NT Advanced Server 3.1

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