# Towards Flexible Integration of 5G and IIoT Technologies in Industry 4.0: A Practical Use Case
## 3 Building Technologies
### NFV and SDN  
As previously stated, the core technologies that realize the proposed infrastructure are NFV and SDN. Each of them plays a critical role in enabling a more agile, flexible, and cost-efficient provisioning of network services.  
NFV technology is concerned with the abstraction, or decoupling, of network functions from physical hardware. Thanks to virtualization, a plethora of application services (such as data processing services) and network services (such as firewalls and NAT) that have traditionally run on dedicated servers and appliances can be relocated into commodity hardware as virtual services. Each of the hardware servers comprising an NFV infrastructure exposes their available physical resources (such as CPU, memory disk, and network interfaces) as virtual resources, and each virtual service or virtual service component is assigned a specific portion of these virtual resources on demand. Virtual services can be deployed in an isolated fashion regardless of the hardware server that they have been allocated into.  
The NFV architectural framework standardized by the European Telecommunications Standards Institute (ETSI) is depicted in Figure 2 below. The NFV Infrastructure (NFVI) comprises the totality of the physical resources, possibly including resources from different locations or domains. These physical resources may include computing, storage, and networking resources, and together build the environment that is capable of supporting the creation of Virtual Network Functions (VNFs). A virtualization layer in the NFVI abstracts these hardware resources into a pool of virtual resources that can be conveniently sliced and allocated to multiple VNFs.  
In NFV, the intelligence is provided by the NFV Management and Orchestration (MANO) block. MANO performs all the actions that involve the life cycle management (e.g., creation, configuration, and termination) of the aforementioned VNFs. Furthermore, a Network Service (NS) can encompass multiple VNFs providing a broader service on the whole. MANO can be subdivided into the Virtualized Infrastructure Manager (VIM), and a higher level NFV Orchestrator (NFVO). The VIM is responsible for the interaction with the NFVI resources across one domain during VNF allocation and deallocation tasks, whereas the NFVO works at the level of NSs and VNFs, managing their life cycle.  
In an NFV/SDN scenario, if NFV technology realizes the deployment of services leveraging virtualization mechanisms, SDN is the technology that realizes the interconnection of those services and their components. Traditional networking has been implemented in such a way that the functionality to forward the network packets and the functionality to decide how they are forwarded are contained in the same device. These functionalities are known as data plane and control plane, respectively.  
As represented in Figure 3, SDN thrives on the separation of these two planes to enable the implementation of a more centralized control plane in which each forwarding device is no longer responsible for making their own forwarding decisions. Instead, control plane tasks are relegated to one or more centralized controllers possessing a broader view of the whole network topology and conditions. These controllers enforce the forwarding logic into each device, which now only has to execute data plane tasks (packet forwarding). Thus, network devices do not need to use specific protocols and exchange information between them in order to make coherent forwarding decisions. SDN also results in greater programmability and reconfigurability of the network thanks to the centralization of the forwarding intelligence and the high granularity provided in the classification of network traffic.  
Figure 2: ETSI NFV reference architectural framework.