Erreur sur l'installation de ns-2

Bonjour,
j'ai des soucis dans l'installation de ns-allinone-2.33. en effet, lorsque je lance l'installation , tout se passe bien jusqu'au moment ou il l'installe otcl. et je reçois le message:

checking for main in -lXbsd... no
checking for socket in -lsocket... no
checking for gethostbyname in -lnsl... yes
checking for dcgettext in -lintl... no
checking for getnodebyname in -ldnet_stub... no
checking that g++ can handle -O2... no
checking standard STL is available... no
checking for tcl.h... -I../include
checking for tclInt.h... -I../include
checking for libtcl8.4... -L../lib -ltcl8.4
checking for init.tcl... ../lib/tcl8.4
checking for http.tcl... ../lib/tcl8.4/http1.0
checking Tcl http.tcl library... yes
checking for tclsh8.4.18... no
checking for tclsh8.4... ../bin/tclsh8.4
checking for tk.h... -I../include
checking for libtk8.4... -L../lib -ltk8.4
checking for tk.tcl... ../lib/tk8.4
checking for X11 header files
can't find X includes
otcl-1.13 configuration failed! Exiting ...

Merci de bien vouloir me repondre