AbstractAccurate measurement and modeling of IP networks is essential for network design, planning, and management. Efforts are being made to detect the state of the network from end-to-end measurements using different techniques and paradigms. In this paper we propose a novel concept to use in the modeling of real network scenarios under measurement and analysis. We called this new concept Service Condition. We explain our proposal's motivations and we use some simple examples to show how to apply the Service Condition concept to the study of real heterogeneous network scenarios. To show the real applicability of our proposal, preliminary results from a performance evaluation study over real heterogeneous networks (where the integration of LAN, WLAN, ADSL, UMTS, and GPRS is present) are given.