Tcp1323Opts : This is used when an application requests a Winsock socket to use buffer sizes greater than 64K. Time stamps enable computers to measure round trip times and to reject old duplicate packet segments. TCPLW and time stamps are useful for networks that have high bandwidth and high delay, such as high-speed transcontinental connections or satellite links. By default, TCPLW will be used if an application requests a Windows Sockets 2 socket to use a buffer size greater than 64 KB or if a DefaultRcvWindow size of more than 64 KB is used in the registry. It is documented in RFC 1323.

MaxDupAcks : MaxDupAcks Fast Retransmission and Fast Recovery of TCP connections that are encountering IP packet loss in the network. Allow a TCP sender to quickly infer a single packet loss by reception of duplicate acknowledgements for a previously sent and acknowledged TCP/IP packet. This mechanism is useful when the network is intermittently congested and intervening routers or switches are dropping packets.

Support For Selective Acknowledgements (SackOpts) : It allows TCP to recover from IP packet loss without resending packets that were already received by the receiver. It is most useful in combination with TCPLW and time stamps. It is documented in RFC 2018.