 inter-system communication between the MEC platforms. Below we describe a possible implementation of these hierarchy levels for inter-MEC sys- tem communication. At the time of writing this book, these mechanisms are not yet part of the ETSI MEC specifications. 6.4.5.1 Possible Implementation The information exchange required to support the inter-MEC system communications described above can be implemented in different ways, for example, at MEC orchestration, at MEC platform management, or at MEC platform level. Figure 6.4.9 illustrates the possible levels of interactions for the inter-MEC system communication. Communication among MEOs for MEC system discovery: Using a V2X communication system as an example, the ITS operator, or the mobile oper- ator, has to rely on multiple different MEC systems deployed in some "ITS service areas," e.g. in a country or across the border, in order to provide consistent ITS services in that area. In this case, the operator may define a set of MEC systems (and their IDs) deployed in this "ITS service area." The set of MEC system IDs is communicated to all MEOs, e.g. by means of a dedicated reference point, SO that every MEC system is aware of the set of other systems it may need to communicate with. Such inter-MEO communication may take place periodically, depending on the rate of deploying new MEC systems in the "ITS service area." Communication among MEC platform managers for MEC platform discovery: Once the communication interface between two MEC systems has been established, the next step is MEC platform discovery between these systems. In this step the MEPM of each system constructs the ID of available MEC host IDs under its control, e.g. those MEC System #1 MEC System #2 Consumer Provider MEC app Service MEC Platform MEC Platform Figure 6.4.9 Graphical representation of the layered/hierarchical approach for inter-MEC system communication. 6 Enabling Technologies which are not under maintenance and have sufficient processing, memory, storage, and potentially other resources.