Discrete event simulator targeted at networking research

 Provides substantial support for simulation of TCP, routing,
 and multicast protocols over wired and wireless (local and satellite)
 networks.
 Ns-2 is written in C++ and an Object oriented version of Tcl called OTcl.
 .
 Ns began as a variant of the REAL network simulator in 1989 and has
 evolved substantially over the past few years. In 1995 ns development
 was supported by DARPA through the VINT project at LBL, Xerox PARC,
 UCB, and USC/ISI. Currently ns development is support through DARPA
 with SAMAN and through NSF with CONSER, both in collaboration with
 other researchers including ACIRI. Ns has always included substantal
 contributions from other researchers, including wireless code from the
 UCB Daedelus and CMU Monarch projects and Sun Microsystems.