The Complete Guide to the OSI Model

This complete guide isn’t yet finished or published. This is a preview.

Computer Networking is a very complex area to study. In courses, people often find themselves struggling more over networking than they do architecture. Ironically this is because it is easier, and is explored more in depth in intermediate to advanced courses. Commonly “The OSI Model” will be used to illustrate the structure of computer networking. This series of articles explores what the OSI Model actually is, and why it is necessary. It will also provide an example for each layer using a non-computing based approach.

What is the OSI Model?

The OSI Model is a standard developed by ISO (one of their jobs is to create international standards for all fields, not only computing) to ensure that all types of different computing devices can communicate with each other. When I say “devices” I mean all aspects of each device (for example)…

  • Hardware:- Routers from different manufacturers must be able to communicate with each other otherwise we would have millions of networks unable to communicate and transmit data to one another. The internet certainly wouldn’t be possible without every network being able to communicate.
  • Software:- For example, the predominant client operating system, Windows, must be able to communicate with the predominant server operating system, Linux. Otherwise we’d have Linux web servers unable to send websites to Windows clients!

So the OSI Model crosses both the software and hardware divide and creates clear standards that developers must follow if they want their technology to communicate successfully with other gadgets!

Lego House

James May wants to send his lego house to a friend.

James May wants to send his lego house to a friend.

At Linux Student, we like to always remember how similar the OSI Model is to something physical like packages being sent through the mail. There are various similarities, and this helps us to make the connection between layers.

Click here to read our Lego House Example >>

Layers of the OSI Model

Layers can be difficult to understand. As we work our way down the different layers to transmit information, each layer will add it’s own information to our packet.

Tip:- An easy way to learn the order of the layers from 1 – 7: “Please do not touch Steve’s pet alligator”

7. Application Layer
6. Presentation Layer
5. Session Layer
4. Transport Layer
3. Network Layer
2. Data Link Layer
1. Physical Layer

Tip:- For learning purposes, working backwards is recommended as it’s easier to understand what’s happening (Layer 7 first).


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