Windows NT Clients Run Out of Ports

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

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.

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

   HKEY_LOCAL_MACHINE\CurrentControlSet\Services\Tcpip\Parameters

   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