Windows NT Clients Run Out of Ports

ID: Q149532

The information in this article applies to:

Microsoft Windows NT Workstation version 3.51
Microsoft Windows NT Server version 3.51

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information on how to do this, view the "Restoring the Registry" online Help topic in Regedit.exe or the "Restoring a Registry Key" online Help topic in Regedt32.exe.

SYMPTOMS

Event id 2009 'Number of sessions exceeds 2048' may be recorded in the event log and/or clients may be unable to create new connections to the server.

CAUSE

Windows NT clients using excessive numbers of ports (more than 3,976 simultaneously) may run out of ports before TCP/IP releases closed connections. The TCP/IP state machine dictates that when a connection is closed, the connection is not released until two maximum segment lives (MSLs) have passed. This state is defined as the TIME-WAIT state. Because one MSL is defined as 120 seconds, it takes 4 minutes for a closed connection 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 problem, install the fix mentioned below.

A new registry has been added to TCP/IP to allow the TIME-WAIT state to be configurable. This will allow TCP/IP users to free closed connection resources more quickly.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

The new registry entry is to be added to the following registry key:

HKEY_LOCAL_MACHINE\System\CurrectControlSet\services\Tcpip\Parameters

The 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 NT Workstation version 3.51 and Microsoft Windows NT Server version 3.51. This problem was corrected in the latest U.S. Service Pack for Windows NT Workstation or Server version 3.51. For information on obtaining this update, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

MORE INFORMATION

For information about configuration options for Windows NT 4.0, please see the following article in the Microsoft Knowledge Base:

ARTICLE-ID: Q170359
TITLE : How to Modify TCP/IP Maximum Retransmission Timeout

Keywords : kbnetwork nttcp kbbug3.51 NTSrvWkst
Version : WinNT:3.51
Platform : winnt
Issue type :