In addition, Windows 2000 has the following performance enhancements: Protocol stack tuning, including increased default window sizes and new algorithms for high delay links, which increases throughput TCP-scalable window sizes (supported by RFC 1323) Selective acknowledgments (SACK) TCP fast retransmit Round Trip Time (RTT) and Retransmission Timeout (RTO) calculation improvements Improved performance for management of large numbers of connections Hardware task offload mechanisms