Adjust TCP Max Retransmission Timeout in Regedit

This article explains how to adjust the system-wide TCP maximum retransmission timeout parameters in Windows using the Registry Editor (Regedit). Modifying these settings controls how many times the operating system attempts to retransmit unacknowledged data packets before terminating the connection, which is essential for optimizing network behavior in high-latency or unstable environments.

Step 1: Open the Windows Registry Editor

  1. Press Win + R on your keyboard to open the Run dialog box.
  2. Type regedit and press Enter or click OK.
  3. If prompted by User Account Control (UAC), click Yes to grant administrative privileges.

Step 2: Navigate to the TCP/IP Parameters Key

In the Registry Editor, use the left-hand navigation pane to browse to the following path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Alternatively, you can copy and paste this path directly into the address bar at the top of the Registry Editor window and press Enter.

Step 3: Modify or Create the Retransmission Parameters

To adjust the maximum retransmission attempts for active data transfers, configure the TcpMaxDataRetransmissions value.

  1. In the right-hand pane of the Parameters key, look for the entry named TcpMaxDataRetransmissions.
  2. If the entry does not exist:
    • Right-click an empty space in the right pane.
    • Select New > DWORD (32-bit) Value.
    • Name the new value TcpMaxDataRetransmissions and press Enter.
  3. Double-click TcpMaxDataRetransmissions to open its edit window.
  4. Under Base, select the Decimal radio button.
  5. In the Value data field, enter the desired number of retransmissions:
    • Default: 5 (retries 5 times before dropping the connection).
    • Lower values (e.g., 2–3): Aborts failed connections faster.
    • Higher values (e.g., 6–10): Gives connections on slow or lossy networks more time to recover.
  6. Click OK to save the value.

Optional: Adjust Connection Handshake Retransmissions

To adjust the timeout for initial SYN connection attempts rather than active data transfers:

  1. In the same Parameters folder, look for or create a DWORD (32-bit) Value named TcpMaxConnectRetransmissions.
  2. Double-click it, select Decimal, and set the value:
    • Default: 2 (Windows retries the SYN packet twice, with doubling timeouts, before giving up).
  3. Click OK.

Step 4: Restart the System

TCP/IP stack registry changes do not apply dynamically. Close the Registry Editor and restart your computer to apply the updated TCP retransmission parameters across the entire system.