ns-3.25 was released on 24 March 2016 and features the following significant changes.

• A new traffic control framework, inspired by the Linux traffic control subsystem, has been introduced to allow experimentation with Internet-aware active queue management (AQM) techniques, packet filtering, and policing. The existing network device queues were reworked, a Linux-like pfifo_fast queuing discipline was added, and existing AQM queue models (CoDel, RED) were ported to the new framework. The RED queue model was extended to support Adaptive RED.
• The Wi-Fi module adds additional support for 802.11n and 802.11ac modes, including better support for larger channel widths and multiple spatial streams (MIMO), and a simplified helper API for MPDU and MSDU aggregation. Two adaptive rate controls for 802.11n/ac, Ideal and MinstrelHt, have been added. Finally, backward compatibility between 802.11g access points and 802.11b stations, and between 802.11n/ac and legacy stations, has been added.
• The Internet module features a refactored TCP model to better support testing and to support modular congestion control classes. A RIPv2 routing protocol implementation was also added to the Internet module.

Finally, the release includes numerous bug fixes and small improvements, listed in the RELEASE_NOTES.

• The latest ns-3.25 source code can be downloaded from here
• What has changed since ns-3.24? Consult the changes page.
• The documentation is available in several formats from here.
• Errata containing late-breaking information about the release can be found here
• A patch to upgrade from the last release (ns-3.24.1) to ns-3.25 can be found here