# 5G-MEC Testbeds for V2X Applications
## 2 Background
### Fundamentals of ETSI-MEC
#### 2.2.1 MEC Architecture  
The MEC architecture provides an extensive high-level overview of the MEC system, enabling MEC applications to operate uninterrupted in a multi-access network. The MEC system reference architecture comprises an MEC management entity and one or more MEC hosts (MEHs) [20]. Figure 3 depicts the MEC system reference architecture defined by the ETSI. Below, we present the different architectural elements (referred to in this paper as MEC building blocks).  
_MEC Host_  
An MEH is an element that contains the MEC Platform (MEP); the Virtualization Infrastructure (VI), which is a set of computing and storage resources; and the network for the MEC applications (MEC apps). The data plane in the VI performs the traffic rules received by the MEP. The MEP routes the traffic among other services, applications, and access networks. Usually, these functions are run on Virtual Machines (VMs) that provide specific network services, with isolation supported by virtualization.  
_MEC Platform_  
The MEP is an integral component that delivers a set of tasks necessary for MEC apps to run on a specific VI, configures the DNS proxy and server, and provides an environment that both offers and leverages MEC services. It is up to the MEP to grant access to storage and time-of-day data.  
_MEC Management_  
The MEC management entity consists of two components, MEC system-level management and MEC host-level management. MEC system-level management interacts with  
Figure 3: ETSI MEC reference architecture.  
MEC host-level management and the access network. MEC system-level management consists of the following elements:  
* _MEC Orchestrator (MEO)_, which is the brains of the MEC as it contains the complete global overview of the MEHs, services, resources, and topology. It determines the most appropriate MEH based on the user requirements. An MEO can perform system-level tasks with the Operating Support System (OSS) and the user application life cycle management proxy. It can trigger application termination, relocation, and instantiation as needed.
* _OSS_, which receives requests via the Customer Facing Service (CFS) portal and makes decisions based on these requests that enable or terminate applications. For further processing, an MEO handles the requests. Where supported, the OSS can receive requests to relocate applications between the MEC system and the cloud.
* _User Application Life Cycle Management Proxy_, which is an MEC application used for the life cycle management of UE applications. It enables device applications to trigger instantiation, onboarding, and application termination for users, where supported. It is a function that can be accessed from the mobile network and can inform the state of the user application to the device application. For further processing of the requests, it interacts with the MEO and the OSS. MEC host-level management consists of the following elements:
* _MEC Platform Manager (MEPM)_, which is responsible for a set of applications that provide critical information to the MEO concerning the MEP, provide information about the life cycle management of MEC apps, configure the DNS, manage rules, and authorize services.
* _Virtualization Infrastructure Manager (VIM)_, which allocates and manages the virtualized resources of the VI. It provides a virtual environment to host a VM and can rapidly deploy applications, where supported. It gathers and reports on the state of the performance and fault information of the virtualized resources.