cc_chd -- CHD Congestion Control Algorithm

New in FreeBSD 8.3 and 9.0 is a choice of TCP/IP congestion modules.

http://www.FreeBSD.org/cgi/man.cgi?query=cc_chd&sektion=4&manpath=FreeBSD+9.0-RELEASE

     CHD enhances the HD algorithm implemented in cc_hd(4) provides tol-       erance to non-congestion related packet loss and improvements to coexis-       tence with traditional loss-based TCP flows, especially when the bottle-       neck link is lightly multiplexed.         Like HD, the algorithm aims to keep network queuing delays below a par-       ticular threshold (queue_threshold) and decides to reduce the congestion       window (cwnd) probabilistically based on its estimate of the network       queuing delay.