Starting with SP4, you can control the delayed ACK timer.

Delayed ACKs reduce the number of packets sent on the network. An ACK is only sent when either of the following occurs:

- No ACK was sent for the previously received segment.

- No segment arrives within 200 milliseconds (the default), after receiving a segment.

An ACK is normally sent for every other received segment, unless the delayed ACK timer expires.

To alter the delayed ACK timer, navigate to:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\<interface_name>\Parameters\Tcpip

On the Edit menu, Add Value name TcpDelAckTicks, as a type REG_DWORD. In the DWORD Editor, enter a number in the range of 0 through 6. The default is 2.

NOTE: Entering a 0 disables the delayed ACK timer, causing an immediate ACK for every packet received.

You must shutdown and restart Windows NT.

NOTE: For Windows 2000+, the path is:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<Interface_GUID>

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