Registry Guide for Windows

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

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Home > Network > Protocols > TCP-IP

(Windows NT/2000/XP)
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.

This tweak can be easily applied using WinGuides Tweak Manager.
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Open your registry and find or create the key below.

Create a new DWORD value, or modify the existing value, called "SackOpts" and set it according to the value data 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\P...

Registry Settings

System Key: [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters]
Value Name: SackOpts
Data Type: REG_DWORD (DWORD Value)
Value Data: (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