First Thing's First
Learn the OSI model below. This is the best place to start for ANYONE transitioning into tech. Even though it is listed 1-7, visually it is bottom up. A great way to remember it is PLEASE DO NOT TOUCH STEVE'S PET ALLIGATOR.
Physical
The physical layer is the lowest layer of the OSI model. Its key responsibility is to carry the data across the physical hardware such as an Ethernet cable to the destination.
Data Link
At this layer the physical address (MAC Address) is added to the data, this includes the source and destination MAC address.
Network
The network layer handles IP address routing. At this stage of the OSI model the source and destination IP address is added to the data.
Transport
The transport layer of OSI Model is used for error handling and sequencing to unsure no data is lost. This layer also adds source and destination port numbers
Session
This layer is responsible for establishing and terminating of connections between devices.
Presentation
This layer formats the data in a way that the receiving application can understand it. This layer is also able to encrypt and decrypt date if needed.
Application
This layer is where the application and user communicate. Application specific protocols are used here such as SMTP (simple mail transfer protocol) for sending emails from Outlook.
Here's a video further breaking down the OSI
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