The OSI Model...

One of the first things that you begin to learn about in the CCNA course is the OSI model. Up until recently I’d never heard of the layers of the OSI model and so it’s taken a some time to become familiar with what each layer of the model does.

The OSI (Open Systems Interconnection) was created by the International Organisation for Standardisation (ISO) as a framework used to describe how data is transferred over a medium from one networked device to another. It is made up of 7 layers:

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

The 4 main advantages of the OSI are:

1. It divides the communication process into simpler components, aiding component development, design, and troubleshooting.
2. It encourages industry standardization by defining what functions occur at each layer of the model.
3. It prevents changes in one layer from affecting other layers, so that it does not hamper development.
4. It allows various types of network hardware and software to communicate.

Below is my summary chart of the OSI model...