This first section offers an introduction to essential networking concepts, with a strong focus on the TCP/IP stack.

The following discussion is based on Internet Protocol version 4 (IPv4). Since the internet has run out of IPv4 addresses, a new version, IPv6, has been developed, which is intended to resolve this situation. However, although IPv6 is being used in a few areas, its deployment is progressing slowly and the majority of the internet will likely be using IPv4 for a while longer. We'll focus on IPv4 in this section, and then we will discuss the relevant changes in the IPv6 section of this chapter.