Microsoft Knowledge Base Article 224829 contains the following summary:

This article describes the following TCP features in Microsoft Windows 2000 and Microsoft Windows Server 2003:

• TCP Window Size                               • TCP Options Now Supported                               • Windows Scaling - RFC 1323                               • Timestamp - RFC 1323                               • Protection against Wrapped Sequence Numbers (PAWS)                               • Selective Acknowledgments (SACKS) - RFC 2018                               • TCP Retransmission Behavior and Fast Retransmit
The TCP features can be changed by changing the entries in the registry.