This is ns-3-allinone.

If you have downloaded this in tarball release format, this directory
contains some released ns-3 version, along with 3rd party components
necessary to support all optional ns-3 features, such as Python
bindings and the Network Animator.  In this case, just run the
script build.py; all the components, plus ns-3 itself, will thus be
built.  This directory also contains the bake build tool, which allows
access to several additional modules including the Network Simulation
Cradle, Direct Code Execution environment, and click and openflow 
extensions for ns-3.

If you have downloaded this from mercurial, the download.py script will
download bake, netanim, pybindgen, and ns-3-dev.  The usage to use
basic ns-3 (netanim and ns-3-dev) is to type:
./download.py
./build.py
and cd into ns-3-dev for further work.  Consult the bake documentation
on how to use bake to access optional ns-3 components.