Computational grids are probably among the most heterogeneous computing systems. However, they are very attractive for their potential computational power. Their heterogeneity is especially perceptible during the deployment of grid applications. This paper presents a description model of (grid) networks which provides a synthetic view of the network besides multiple protocols. The authors have developed the simulation tool for support performance-oriented development of scheduling in grid applications. A simulation environment, on the other hand, may be ideal for this evaluation purpose as virtually all factors within a simulated VO (Virtual Organization) can easily be modified for evaluation.