This paper describes the Scalable Simulation Framework (SSF), a
discrete event modeling API designed for the construction and
simulation of very large networks. SSF can execute detailed
simulations of complex topology networks with a million or more
concurrent TCP/IP flows. We describe the overall architecture of SSF,
the architecture of the network modeling layers above the basic API
structure, and discuss preliminary performance figures for up to
100,000 concurrent TCP flows in a test topology.