**3.1.1 Conceptual level**

From a conceptual point of view, two issues are especially important: the elements that manage architecture's behaviour and the ways in which the different applications (terrestrial and on-board) transmit the information.

Our architecture hosts both terrestrial and train-side applications, so in order to manage its behaviour two main entities are defined: Terrestrial Communication Manager (TCM) and On-board Communication Manager (OCM). The former manages terrestrial aspects of the architecture and the latter train-side issues. Although the managers have a different physical location, both of them have nearly the same responsibilities:


Due to the information transmission needs and for a correct and optimized used of the communication architecture, two types of communications are distinguishes: "slight" and "heavy" communications. These two types take into account characteristics of both information and communication technologies, such us: the volume and the priority of the information, the existence of coverage, and the cost of the communication.

