Layer 1 is the Physical Layer. It deals with the physical connection between devices, like cables and switches. In my experience, this is where you'll find issues related to cabling, like loose connections or damaged wires.
Layer 2 is the Data Link Layer. It's responsible for creating a reliable link between two directly connected devices. This layer uses MAC addresses to identify devices and ensures data is delivered error-free. A useful analogy I like to remember is that it's like a postal worker ensuring that a letter is delivered to the right mailbox.
Layer 3 is the Network Layer. It's responsible for routing data between different networks. It uses IP addresses to identify devices and determines the best path for data to travel. I've found that this layer is crucial for understanding how data moves across the internet.
Layer 4 is the Transport Layer. This layer is responsible for end-to-end communication between devices, ensuring data is delivered reliably and in the correct order. It uses protocols like TCP and UDP to manage data transmission.
Layer 5 is the Session Layer. It establishes, maintains, and terminates connections between devices. In my experience, this layer is like a traffic cop, coordinating communication between applications on different devices.
Layer 6 is the Presentation Layer. It deals with the presentation of data, including encryption, compression, and data formatting. I like to think of this layer as a translator, ensuring that data is readable by both the sender and receiver.
Layer 7 is the Application Layer. It's the interface between the user and the network, providing access to various network services. From what I've seen, this layer is where you'll find your email client, web browser, and other applications that interact with the network.