With the increased attention ATM is receiving to meet the needs of a wide variety of applications, tools are needed to help a network designer focus on the design at hand, rather than to spend time exhaustively learning the tools themselves. This is the concept behind IDEA. This paper introduces ``modeling engines'' chosen to be integrated into IDEA and presents a user interface for networking design. The first objective for IDEA is to demonstrate its usefulness for dependability modeling. Later objectives include incorporating performance and performability modeling.