TCP Congestion Control Algorithm of OSX10.7
This Stack Overflow question should help: How to load a different congestion control algorithm in Mac OS X?


  The LEDBAT congestion control algorithm is built into OSX Lion
  (10.7.X) and does not need to be compiled separately. I don't think it
  would be possible to use LEDBAT in an earlier version of OSX without
  alot of work. LEDBAT provides for 'background' transfers and may be
  selected on a socket by setting the following socket option -
  setsocketopt(sock, SOL_SOCKET, O_TRAFFIC_CLASS, SO_TC_BK,
  sizeof(int)). It also seems that the socket's traffic class may
  affected by the DSCP value in the IP header.
  
  Additionally OSX has had the facility to load kernel modules for other
  network protocols for some time using their Network Kernel Extensions
  (NKE) - for example there is an NKE module that has been developed for
  the SCTP protocol.


Alternatively, another related question might be useful: How do you set the TCP congestion control algorithm on OS X?


  According to
  http://www.macgeekery.com/gspot/2006-03/mac_os_x_network_tuning_guide
  you can actually modify the algorthims used by Mac OS X by using the
  sysctl command, but you cannot use anything but the New Reno algorithm