RFC 1323 (http://www.cis.ohio-state.edu/htbin/rfc/rfc1323.html)
This memo presents a set of TCP extensions to improve performance
over large bandwidth*delay product paths and to provide reliable
operation over very high-speed paths. It defines new TCP options for
scaled windows and timestamps, which are designed to provide
compatible interworking with TCP's that do not implement the
extensions. The timestamps are used for two distinct mechanisms:
RTTM (Round Trip Time Measurement) and PAWS (Protect Against Wrapped
Sequences).
Windows Scaling
For more efficient use of high bandwidth networks, a larger TCP window size may be used. The TCP window size field controls the flow of data and is limited to 2 bytes, or a window size of 65,535 bytes.
A scaling factor is used to allow and increase in the maximum window size from 65,535 bytes to 1 Gigabyte.
Time Stamp
The Time Stamp Option
is used to help calculate the Round Trip Time (RTT) of packets transmitted.
This is required when window scaling is used over long-ping-time high-throughput networks.
Windows 2000 and Windows Me support
these options. Windows 98 needs a vtcp update from Microsoft to support these options.
(The update is included in Niwot's Gigabyte Express 5 and Gigabyte Express 3 products).
Tcp1323Opts
The Tcp1323Opts value in the following registry key can be edited to control scaling windows and timestamp:
Windows 2000:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services Tcpip\Parameters\Tcp1323Opts
Windows 98/Me:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP\Tcp1323Opts
NOTE: The valid range is 0,1,2 or 3 where:
0 (disable RFC 1323 options)
1 (window scale enabled only)
2 (timestamps enabled only)
3 (both options enabled)
TcpWindowSize
The TcpWindowSize value in the following registry key can be edited to control scaling windows:
Windows 2000:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services Tcpip\Parameters\TcpWindowSize
Windows 98:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP\GlobalMaxTcpWindoSize
Windows Me:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP\GlobalMaxTcpWindowSize
NOTE: The valid range for window size is 0-0x3FFFC000 Hexadecimal.
NOTE: The spelling may have been fixed in Windows 98. To be sure, we set both entries.
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