Note on Experimental High-speed TCP

• 1.130 Sun Dec 30 4:52:31 US/Pacific 2001 by sfloyd
  Added wnd_option_=8 for experimental algorithm for highspeed TCP.
  Also added two variables for tracing, ncwndcuts_ (number of times slowdown() was called), and necnresponses_ (number of times slowdown() was invoked because of ecn marks).
  Code from Sylvia Ratnasamy.

• Fri Mar 29 5:06:33 US/Pacific 2002 by sfloyd
  Adding variables for experimental high-speed TCP, and cleaning up the code. Changes by Sally Floyd and Evandro de Souza.

The modification to slow-start was added in April 2002, and is described in the CVS log for tcp.cc, as follows:

• Tue Apr 23 5:07:17 US/Pacific 2002 by sfloyd
  Added max_ssthresh_ to limit the slow-start threshold during the initial slow-start. Validated in "./test-all-tcpHighspeed tcp1A" in tcl/test.

• Mon Apr 29 1:56:39 US/Pacific 2002 by sfloyd
  Modifications to the initial slow-start when the new variable max_ssthresh_ is used to limit the initial slow-start. During the initial slow-start, the sender increases its congestion window by at most max_ssthresh_/2 packets each round-trip time, when max_ssthresh_ is not set to zero. When max_ssthresh_ is set to zero, it is ignored, and the standard slow-start is used.

  Agent/TCP set windowOption_ 8

  Agent/TCP set max_ssthresh_ 100

• The current HighSpeed TCP code in NS calculates the increase and decrease parameters anew for each packet. The code would run much more efficiently if a table was created at the beginning of the simulation, as described in the internet-draft, and the TCP sender simply looked up its increase or decrease parameter in the table.