Ns-allinone is a package which contains required components and some of optional components used in running ns. The package contains an "install" script to automatically configure, compile and install these components. If you haven't installed ns before and want to quickly try ns out, ns-allinone may be easier than getting all the pieces by hand.
Update to Tcl/Tk 8.5 series (becoming the default Tcl/Tk version on many platforms)
Update for Cygwin-1.7.1 release for Windows
New features for ns-2.35 release (see the ns-2/CHANGES.html file)
sudo apt-get install tcl8.5-dev tk8.5-dev
sudo apt-get install build-essential autoconf automake
sudo apt-get install perl xgraph libxt-dev libx11-dev libxmu-dev
cd /path-to/ns-allinone-2.35
./install
export PATH=$PATH:/path-tons-allinone-2.35/bin:/path-to/ns-allinone-2.35/tcl8.5.10/unix:/path-to/ns-allinone-2.35/tk8.5.10/unix
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path-to/ns-allinone-2.35/otcl-1.14:/path-to/ns-allinone-2.35/lib
export TCL_LIBRARY=$TCL_LIBRARY:/path-to/ns-allinone-2.35/tcl8.5.10/library
Ns-allinone is available from http://sourceforge.net/projects/nsnam or http://www.isi.edu/nsnam/ns/ns-build.html
The nsnam Project http://www.nsnam.org