TCP and UDP are the main protocols in layer 4 that provide connectivity between end applications. Whenever you start an application from one side to another, you start the session from a source port, usually a random number equal to or higher than 1,024, and connect to a destination port, which is a well-known or registered port that waits for the session on the other side. These are the port numbers that identify the application that works over the session.
Other types of filters refer to other fields in the UDP and TCP headers. In UDP, we have a very simple header with very basic data, while in TCP we have a more complex header that we can get much more information from.
In this recipe, we will concentrate on the possibilities while configuring TCP and UDP display filters.