utage predictively. How is the network going to be scaled in or out? Network scaling is largely an automated task nowadays. It is possible to automate a network controller that can proactively determine the usage of each of the network applications and hardware, and when the usage is above a certain threshold, it can spawn new nodes. At the same time, if a certain application is underutilized, it can scale down to free up computes. Hence, scaling in and out can be an on-the-fly operation with some added manual inputs from operators in the final stages. How is the network going to be tested? It is a valuable investment to onboard a network-testing framework right from the time of an early proof of concept or lab testing. Such a testing framework can not only test the individual network component but the entire network as a whole. Performance and regression tests can be scheduled at predefined intervals SO that defects can be caught well before they are found in production. The answers to these questions will certainly iron out most of the design requirements. Next, we will go over the basic components needed to complete a call in a 5G SA network and how they interact with each other to register a device and establish a Protocol Data Unit (PDU) 5G session. 5G SA network components and end-to-end call flow The following diagram denotes the essential network functions that participate to establish a call between two users - in this example, John and Jane: 5G Standalone Networks P-CSCF Internet Figure 11.3 - Essential 5G network functions In the preceding figure, we have depicted two mobile phone users, John and Jane. Both have the latest 5G handsets and are ready to make a call to each other. In Chapter 2, End-to-End Architecture Components, Concepts, Security, and Transport, we learned about the functionality of each of these NFs in detail. Now, let us go over the high-level steps that will take us through the procedure of a data call after the UE has been powered on. Phase 1 - UE registration process The UE registr