What do we mean by network function virtualization, particularly in the context of 5G? We will try to answer that question in this video. In the '90s and until around 2010, mobile network equipment was made up of specific hardware on which the software had to be developed. A switch, for example, was a specific piece of hardware. Since 2010 and now in 2022, hardware is generic. Using standard computers, we can develop software functions for packet switching or data management. We have also seen the development of virtualization techniques, multiple virtual machines running in parallel which are each considered a single standard computer. Elasticity refers to the ability to start or stop a machine whenever necessary, for example, when the load increases or decreases. In a 5G network, everything that we presented in terms of architecture, AMF, SMF, UPF, UDM, and so on, they are functions. They can correspond to virtual machines running on generic hardware. It's important to remember that there is, first and foremost, a physical infrastructure, such as base stations, deployed or distributed across a given area by the operator, for instance, here in the west part of France. The physical infrastructure is made up of standard computers, as well as, link and most often, intermediate routers. SMF, AMF, UPF functions are activity on certain computers. In our example, we assume that there is a UPF to the east, UPF and AMF here, and a little to the south, another UPF. With medium to heavy load, it can be necessary to have UPF in three locations. When the load decreases during night, for example, the number of UPF functions can be reduced. It would be entirely possible to have just one UPF running in the central location, and the computers in the two other towns, could be switched off this saving energy. Elasticity means that there is a so called orchestrator in the computer. The orchestrator is able to start and to release function instances, one example is starting or stopping an SMF or AMF. Elasticity is facilitated on stateless servers, as it removes the need for long and costly context transfers. What's more? Virtualization is a technique that has been used for a while now for http servers. For 5G, the choice was made, as much as, possible to define interfaces between functions using stateless protocols. In this example, we can see all the SBI interfaces. SBI stands for service-based interfaces between the AMF and the SMF, between the AUSF and the AMF, between the SMF and the UDM, and so on. The other interfaces, and of course, the radio interface in particular, but also the interface between the gNB and the UPF, between the UPFs and the interface controlling the UPF, are not SBI. Let's take a little deeper and see what else we can do with virtualization. We know that NFV decouples the physical architecture from the network functions. With this decoupling, we can imagine an operator deploying network slicing. With network slicing, multiple virtual networks are represented on a shared infrastructure, for example, one slice can be dedicated to a specific service, for example, uRLLC. Here is an example in diagram, the operator will have an initial slice eMBB, for example, which aims to offer high-speed access. The functions are primarily deployed on the standard computer, which is upstream in the network. This allows economies of scale to come into play. However, when the aim is to provide low latency, we can imagine that for URLLC slice, all the functions will be carried out on a computer, which is much closer to the terminal. This way, we get much more reactive network. So here, the UPF will be carried out on a local computer. And finally, we can have a slice for massive machine-type communication with processing occurring higher up in the network. Some functions are shared. For example, the AMF is shared, and will be able to inform the terminal which slice it should be positioned on. To manage the different slices, we use a new function called NSSF or network slicing selection function. This function will be able to select the different slices and organize them. In conclusion, the 5G network is a set of network functions. A network function is a coherent group of tasks, which can be carried out on virtual machines using generic hardware. The instance of a given function can be launched and released, depending on the environment. The interfaces between the different functions are called SBIs or service-based interfaces. With network slicing, an operator can deploy multiple virtual networks, each with specific KPIs objectives, on the same physical infrastructure. [MUSIC]
