[ns] error found in source file

sir, when i am running tcl file it give the below error : Segmentation fault (core dumped) now, below .cc,.h and .tcl file is:-- -blue.cc--- #include math.h #include stdlib.h

[ns] How to change default values in ns-default.tcl

Hi, I want to change some of the default values of RED protocol in NS. I tried setting new values in ns-default.tcl and re-compiled, but when I run the simulation NS uses the old default values instead of new ones. Can anyone please tell me how to change the default values in ns? Thank you,