ns-3.12 was released on 31 August 2011. This release is mainly a maintenance release, but contains a few new features and many bugs fixed.

A minor maintenance release, ns-3.12.1, was made on 2 September 2011 to fix a bug in the Python bindings for the PyViz visualizer.

The source code can be downloaded from here while the extensive documentation is available in a variety of formats from here.