The modeling technique used in the MALAN software simulation is called "next event simulation". The view of time taken by next event simulation is important in understanding the design and implementation of the MALAN simulation. MALAN is a general purpose simulation package usable for modeling a wide range of local area network architectures. The MALAN was developed in the spirit of providing a easily modifiable tool for the modeling of communication network protocols and topologies. This chapter briefly describes the operation of each routine followed by a cursory view of the module as a whole. The use module is a group of subroutines and functions that function collectively as that component of the simulation process that models the communications process in local computer networks. Host or processor components generally include computation and control elements, various levels of memory, and input and output peripherals. The Interface unit is the most complex unit with respect to both hardware and software.