On Shortcomings of the ns-2 Random Number Generator

The ns-2 is a widely used network simulation tool which implements a fairly old and weak random number generator (RNG). As the RNG component is used by a variety of other components, it can be seen as one of the most important core components of the ns-2. In this paper we explore weaknesses of this RNG and demonstrate its shortcomings in context with a simple simulation example (M/D/1) which produces severely wrong simulation results when this RNG is used in combination with specific seeds. We incorporate the modern Mersenne Twister RNG into the ns-2 and show how the insensitivity of this RNG regarding to the initial seeds leads to significant improvements in the simulation outputs. Topics: random number generation, correlated random numbers, Mersenne Twister, network simulation, ns-2, M/D/1 Contact: Bernhard Hechenleitner Salzburg Research Jakob-Haringer-Straße 5/III A-5020 Salzburg, Austria email: [email protected] phone: +43.662.2288-445 fax: +43.662.2288-222 This work is partly funded by the EU IST project AQUILA.