Ns-3 projects provide features not available in ns-2, such as a implementation code execution environment (allowing users to run real implementation code in the simulator). Also, Ns-3 projects provides a lower base level of abstraction compared with ns-2, allowing it to align better with how real systems are put together. Some limitations found in ns-2 (such as supporting multiple types of interfaces on nodes correctly) have been remedied in ns-3. Ns3-projects is also actively maintained with an active, responsive user’s mailing list, while ns-2 is only lightly maintained and has not seen significant development in its main code tree also for over a decade.