ns-3.13 is a maintenance-oriented release with an upgrade to the waf build system. The first component from the 2011 ns-3 Summer of Code program, an IPv6 address generator, is included in this release. The spectrum module and TCP models also underwent a significant amount of work during this release cycle, and bug fixes and a full transition to XML based trace file generation were added to NetAnim. Full details are available in the RELEASE_NOTES and CHANGES.html files.