Our smart devices and computers seem to be able to communicate so easily, but in reality, this is because they've been designed for this. Our devices can have hundreds of specifications and these are all allocated logically to different layers of the OSI seven-layer model. 

Imagine that Nicola wants to send a postcard to her sister who is across the world to tell her about her holiday. Nicola buys the postcard, writes a quick message, and then hands the postcard in to the reception at her hotel. The hotel then provides a stamp and delivers the postcard to the post office along with all their other guests' letters and postcards. 

The post office then sorts her postcard into a group with all the other mail that needs to go to the same region and sent off. Once the postcard arrives at its destination, the post office moves it from the incoming mail area to the appropriate holding area. Next, they deliver it to Nicola's mom's house with the rest of their mail. 

When Nicola's mom fetches the post, she finds the postcard waiting for her along with all her other mail. She sorts her mail and leaves the postcard on Nicola's sister's desk. Each step in the process of getting the postcard to Nicolas' sister is important and had its own role to play. 

The OSI seven-layer model works in the exact same way. When you want to send information to another device, it will move down through each of the layers being tagged and encoded along the way with different information. It will then be sent via layer one, the physical layer, over to the target device. 

Once it reaches the target device, it moves up through the layers, where the information will be verified before it finally reaches the user. The important thing for you to remember at this point is that each of the layers in the OSI seven-layer model has an important role to play. Layers always follow a protocol. Each layer expects to receive services from the layers below them and provides services to the layers above, basically, each layer has its own job description.

Lectures

What is The Cloud? - DHCP and DNS - Firewall - Encryption - Hubs, Switches and Routers - Unicast, Multicast and Broadcast