The first layer of the OSI model is the physical layer. This layer is the most easily-identifiable layer, as it comprises of everything you can see–from your computer to its hardware to the cables connecting the computers. Anything that you can see is in the physical layer.
Even without studying networking, you probably understand the importance of the physical layer. Though you may think of it in other terms. For example, even if you aren’t thinking about exactly how your router allows for you to connect to the Internet, you know that without it, you won’t be able to get online and connect with your friends.
This makes the physical layer unique in that it provides concrete visuals for the otherwise abstract concepts of networking. If you look a little deeper into this basic stage of networking, however, you will encounter one of the more difficult concepts in networking–binary code. For those who haven’t extensively studied networking and coding, binary code can feel a bit confusing.
Binary code is the language in which computers speak, and it is made up of only different combinations of zeroes and ones. It can be very difficult to imagine how anything can read and speak this language, but at the physical layer stage, all the information is still at this basic level.
This means that while the physical layer is easy to identify and can be pointed out even by people with little to no education in networking, it can still be a bit challenging to fully understand. We’ll break it down the best we can:
Information is read in one of two different types of signals: analog (think: radio) or digital. You have probably encountered analog cables before. These cables belong to the physical layer of the OSI model and help in the transmission of information across a network by sending voltages across the network. Analog waves have long been used, being seen both in radio and TV.
A more modern form of transmission is in digital transmission. Digital transmission is another way in which computers can read and interpret binary code in order to read information that is being sent or received.
In short, the physical layer of the OSI model is everything that you can see–from your computer to your cables to your router. This layer is very basic, with the information still being in binary code. The following layer is the data link layer.