SackOpts

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Data type

Range

Default value

REG_DWORD

0 | 1

1

Description

Enables and disables the Selective Acknowledgment (SACK) feature of Windows 2000 TCP/IP. SACK is specified in RFC 2018, TCP Selective Acknowledgement Options.

SACK is an optimizing feature that lets you acknowledge receipt of individual blocks of data in a continuous sequence, rather than just the last sequence number. The recipient can tell the sender that one or more data blocks are missing from the middle of a sequence, and the sender can retransmit only the missing data.

Value

Meaning

0

Disables SACK.

1

Enables SACK.