RFC2581 - TCP Congestion Control Proposed standard set of congestion avoidance features in a TCP implementation. http://www.rfc-editor.org/rfc/rfc2581.txt
RFC1323 - TCP Extensions for High Performance Defines TCP Window Scale option, timestamps, and protection against wrapped sequence numbers (PAWS). http://www.rfc-editor.org/rfc/rfc1323.txt
RFC2018 - TCP Selective Acknowledgement Options Defines SACK (a technique to better recover from multiple packet losses per round-trip time interval). http://www.rfc-editor.org/rfc/rfc2018.txt
RFC2861 - TCP Congestion Window Validation An experimental RFC that addresses revalidation of TCP congestion window after a period of time when connection wasn't network-limited. http://www.rfc-editor.org/rfc/rfc2861.txt