Where is the RED source code located?

[Qin Cai <qcai@eecs.uic.edu>]

Hi, everyone. 

  I'm trying to implement RIO in ns-2. Since RIO is developed from RED, I
try to modify source code for RED. 

  I've modified the C++ code for RED to RIO, but I couldn't find the TCL
source code for Queue/RED. 

  Can anyone with such experience tell me which file I should look into? 

  Thanks in advance.

  Qin Cai