Summary

The most common protocols, organized by the TCP/IP layer they operate at, are presented in Table 5.2 below:

Table 5.2 – TCP/IP Layers and Their Protocols

Port numbers are assigned to different protocols and services so that a user will know how and what to access at the other end and to identify specific applications. They are also used to track the session associated with that protocol.

Well-known port numbers are non-ephemeral ports, meaning they are permanently assigned to a protocol or a service. They can be used as a destination port by any network-enabled machine to reach specific protocols. Temporary port numbers are ephemeral ports that are usually used as source ports in a two-way communication process. They are determined in real-time by the client workstation and are usually numbers above 1024.