rations are End-to-End Architecture Components, Concepts, Security, and Transport possible. It is the operator's choice to select the appropriate combination. The general idea is that closer proximity of these radio components to the UPF will reduce the latency and hence be more appropriate for delay-sensitive applications. The CU is then connected to the mobile packet core by optical fiber. The mobile packet core can be centrally located. It is also possible to regionalize the packet core in cases where the geographical area of a country is large. In this case, there can be multiple regions - for example, least, west, north, south, and central - that cater to the traffic and subscribers in proximity in order to reduce latency. Hence, the determining factor for the design choice is also the geographical area of coverage. Often, the connectivity of the CU to the packet core is via leased lines, SO it is important to ensure the lines are secure and use security protocols to avoid malicious snooping and attacks that can cause denial-of-service. 5G network concepts Multiple NFs come together to make the 5G System (5GS). Each of these NFs has a designated function and is connected to one or more other NFs to provide its services or consume services provided by another NF. 5G almost entirely ushers in the adaptation of virtualized infrastructure. The NFs have been designed to operate over Commercial Off-The-Shelf (COTS) hardware and are no longer complicated or expensive. These NFs are therefore virtualized. They can be virtual machine-based or use microservices- based or bare-metal-based software capable of running microservices directly, bypassing the need for a VM. The 3GPP standards on 5G have been written keeping this microservices-based virtualized infrastructure in mind. Hence, 5G completes the cycle of telecom virtualization that started with 4G and comes full circle with 5G. 3GPP has defined each of these connections between any two NFs, as shown by the reference point architecture diagram in Figure 2.3. Each 