This paper proposes a pragmatic approach for validating, at the design step, real-time in-vehicle applications using CAN (Controller Area Network) as the underlying communication system. By validation, we mean the verification that dependability constraints (e.g. deadlines, jitters, transmission error tolerance) will be met by the designed solution (called the operational architecture and denoted by OA). The verification is performed by evaluating the performance of the OA. Our approach consists, on the one hand, in building models (both analytic and simulation) and analysing them (model-based evaluation), and on the other hand, in monitoring the network(s) on a prototype of the system (prototype-based evaluation). The proposed method, as well as the set of associated software tools, is described with a special emphasis on analytical models. An example is used throughout the paper to illustrate the usefulness of the tools as well as their complementary nature.