HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\ interface-name

Data type


Default value


0x0–0x3FFFFFFF ( bytes )

(See description.)


Determines the largest TCP receive window that the system offers. The receive window is the number of bytes a sender can transmit without receiving an acknowledgment. This entry overrides TCP's negotiated maximum receive window size and replaces it with the value of this entry.

TCP uses a receive window that is four times the size of the maximum TCP segment size (MSS) negotiated during connection setup, up to a maximum size of 64 KB. TCP for Windows 2000 also supports windows scaling, as detailed in RFC 1323, TCP Extensions for High Performance. Scaling enables TCP to provide a receive window of up to 1 GB.

For Ethernet networks, the default value of this entry is 0x4470 (17,520, or 12 segments of 1,460 bytes each). For other networks, the default value is 0xFFFF (65,535) unless 0xFFFF is larger than:

  • Four times the maximum TCP data size on the network; and

  • 0x2000 (8,192) rounded up to an even multiple of the network TCP data size.

Note Image Note

This entry determines the maximum receive window size for this interface. When configuring this interface, this entry takes precedence over the GlobalMaxTcpWindowSize entry, which establishes a maximum window size for all interfaces.

Windows 2000 automatically uses windows scaling if the value of this entry is greater than 64 KB. To disable windows scaling, set the value of the Tcp1323Opts entry to 0 or 2.

Windows 2000 does not add this entry to the registry. You can add it by editing the registry or by using a program that edits the registry.

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