This chapter outlines some of the issues and uses of modeling in the local area network (LAN) environment. It shows the usefulness of modeling as a tool to aid in LAN selection as well as to show the use over the life of a network. Modeling LANs can provide the modeler with insight into the limitations of a proposed network before it is purchased, define bottlenecks in its architecture, aid in the selection of alternatives, or indicate ways in which to configure a proposed system to optimize its performance. There are many tools that can be applied to the modeling of a local area network: analytical modeling, simulation, test beds, operational analysis, and hybrids. Simulations provide us with a means to model the local area network to any level of detail we deem necessary to effectively perform the wanted analysis. Simulation includes a wide spectrum of techniques such as the queuing of discrete events and continuous or hybrid simulations.