How Do I Reduce the Time for Canceling TCP Connections in TIME_WAIT State on Windows

Question

In a large-scale Windows environment, a large number of Transmission Control Protocol (TCP) connections in the TIME_WAIT state exist after Nginx reverse proxy service is adopted. By default, TCP connections in the TIME_WAIT state is canceled in 4 minutes. By default, the dynamical TCP ports ranges from 49152 to 65535. As a result, TCP connections are recycled slowly, which leads to a throughput decrease or access failures (error code: 502). You can modify operating system (OS) kernel parameters to shorten the recycling duration for TCP connections in the TIME_WAIT state and enlarge the dynamical TCP port range. This ensures that OS port resources are available when a large number of clients access the server concurrently.

Answer

1. Log in to the Windows OS as the Administrator user.

   Log in to the server as the SWMaster user if the Windows is hardened.

2. Change the recycling duration for TCP connections.
   1. On Windows, choose Start > Run.
   2. In the Run dialog box, enter regedit and press Enter to open the registry editor.
   3. In the Registry Editor, open HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters.
   4. Choose Edit > New > DWORD (32-bit) Value and enter TcpTimedWaitDelay.
   5. Right-click TcpTimedWaitDelay and choose Modify from the shortcut menu.
   6. In the Base area of the Edit DWORD (32-bit) Value dialog box, set the decimal number to 30 and click OK.
   7. Exit the registry editor.

3. Modify the port range.
   1. On Windows, choose Start > Run.
   2. Enter cmd and press Enter to open the command-line interface.
   3. Run the following command to modify the port range:

      netsh int ipv4 set dynamicportrange tcp startport=5000 numberofports=60000

4. Restart the OS.