Control Selective Acknowledgement (SACK) Operation (Windows NT/2000/XP)

Registry Guide for Windows
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Registry tweaks, tricks & hacks to optimize, enhance and secure Microsoft Windows.

Control Selective Acknowledgement (SACK) Operation (Windows NT/2000/XP)
Category: Home > Network > Protocols > TCP-IP

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This parameter controls whether or not Selective ACK (SACK - RFC 2018) support is enabled. With SACK enabled (default), a packet or series of packets can be dropped, and the receiver informs the sender which data has been received, and where there may be "holes" in the data.

Open your registry and find the key below.

Create a new DWORD value, or modify the existing value called 'SackOpts' using the settings below.

Exit your registry, you may need to restart or log out of Windows for the change to take effect.


(Default)	REG_SZ	(value not set)
SackOpts	REG_DWORD	0x00000001 (1)


	HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters

Settings:

System Key: [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters]
Name: SackOpts
Type: REG_DWORD (DWORD Value)
Value: (0 = disabled, 1 = enabled)

Disclaimer: Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.

Last Modified: August 20, 2002

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