Networks-on-chip, or NoCs, are one communication architecture candidate to be used in present and futures SoCs, due to its scalability, reusability and performance. The focus of this paper is the analysis of IP communication models in NoCs. Employing standard external interfaces, as OCP, is recommended to enable the use of NoCs by different IP core providers. The second point related to reusability is the IP cores communication model. Two basic communication models are considered in this work: NUMA and NORMA. The goal of this work is to evaluate the pros and cons of each communication model, in terms of network interface complexity, area and performance.