The fundamentals

We have already talked about the OSI model. But just as a quick refresher, the OSI model defines the layers that make up the system, allowing us to communicate with other systems. The layers span from the lowest layer, which describes the voltages a network adapter should be able to handle, up to the highest level, which describes the application that uses networking.

A walk down the OSI layers

I want to walk you through all the layers again, detailing what happens in each. To do this, I want to discuss a user using FTP to send data. FTP, which stands for File Transfer Protocol, is an older, hardly used technique to send data to remote machines or to get data from those remote machines.

FTP used to be the best way to achieve that, but the lack of security features made people move to other means. We will discuss some of those later, but we can still use FTP for our walk-down of the OSI model. It makes things a bit easier to understand.

An FTP client can...