Windows NT or 2000 TCP/IP parameters

Two important tuning parameters exist for Windows NT and Windows 2000:

TcpTimedWaitDelay

MaxUserPort

These parameters are set in the Windows registry.

Important: These two parameters should be used together when tuning WAS. Tuning one without tuning the other is not recommended.

 

TcpTimedWaitDelay

Determines the time that must elapse before TCP can release a closed connection and reuse its resources. This interval between closure and release is known as the TIME_WAIT state or 2MSL (twice the maximum segment lifetime) state. During this time, reopening the connection to the client and server costs less than establishing a new connection. Reducing the value of this entry allows TCP to release closed connections faster, providing more resources for new connections.

Consider adjusting this value when the application that is running requires rapid release and creation of new connections, and there is a low throughput due to many connections sitting in TIME_WAIT.

The default value is 0xF0 (240 seconds = 4 minutes), while the recommended value is the minimum value of 0x1E (30 seconds).

To view or set this parameter, use the regedit command, then access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\TCPIP\Parameters and create a new REG_DWORD named TcpTimedWaitDelay. Set the value to decimal 30, which is Hex 0x0000001e. Then restart the system.

By using the netstat command, you will then be able to see that there are fewer connections in TIME_WAIT.

 

MaxUserPort

Determines the highest port number TCP can assign when an application requests an available user port from the system. It is recommended that you set this value to at least decimal 32768.

Using the regedit command, access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\TCPIP\Parameters and create a new REG_DWORD named MaxUserPort. Restart the system.

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