Let me start this chapter with a question. If IPv4 is so widespread and works well, why has IPv6 been released? Quite simply, we've run out (or are running out) of IPv4 addresses. Yes, you read that right. We have run out of 4.2 billion addresses. You might be wondering how this is possible, so let's have a look at some figures.
As of June 2019, Internet World Stats published figures that stated the world population was 7.7 billion (sourced from the United Nations Population Division), and of those, 4.4 billion people were internet users (sourced from the International Telecommunications Union (ITU)). Admittedly, quite a number of those 4.4 billion will be sharing an internet-connected device, such as a home PC, and that will be their only means of connection. But if we flip that, there will be a large number of people who have multiple devices that...