For a while I have been working on a slight change in the way TCP increases it congestion window called appropriate byte counting. The scheme has performance and security benefits (at the cost of increasing burstiness a bit). A few references:

Mark Allman. TCP Congestion Control with Appropriate Byte Counting (ABC), February 2003. RFC 3465.
Mark Allman. TCP Byte Counting Refinements. ACM Computer Communication Review, 29(3), July 1999.
Mark Allman. On the Generation and Use of TCP Acknowledgments. ACM Computer Communication Review, 28(5), October 1998.
Mark Allman. Improving TCP Performance Over Satellite Channels. Master's Thesis, Ohio University, June 1997.

(Posted: Sun Oct 20, 2002; Updated: Thu Feb 6, 2003)