OSI Model Layers Overview

OSI Model

The Open Systems Interconnection model is a framework used by network engineers, computer scientists, and researchers to understand how data moves between devices over networks. It divides communication into seven distinct layers, each with specific functions. These layers are named from zero (Layer Zero) to six (Layer Six), although Layer Zero is sometimes referred to as the physical medium layer. Here's a brief overview of what each layer does:

Session Layer (Layer Five)

The session layer establishes, maintains, and terminates connections between machines. When computers communicate, they need to establish a connection before they can send information back and forth. This process ensures that both sides agree on what kind of connections will be made and how they will be managed.

Transport Layer (Layer Four)

The transport layer provides end-to-end communication services. It breaks large messages into smaller packets and makes sure these packets get to their destination reliably. It also controls the flow of these packets to avoid overwhelming the receiving machine.

Data Link Layer (Layer Two)

The data link layer takes care of moving bits across the physical media. It adds error checking codes to ensure that only correct data gets transmitted. If errors occur during transmission, the data link layer helps retransmit damaged packets.

Physical Layer (Layer One)

The physical layer defines the electrical characteristics of the wire or radio. It determines whether you use Ethernet cables, fiber optic cables, or wireless signals like Bluetooth or Wi-Fi. It also decides how fast the data will move along these wires or through the air.

Network Layer (Layer Three)

The network layer handles routing and addressing. As data travels from one device to another, it needs to know where to go next and how to get there. The network layer uses IP addresses to find the best route between two points and delivers the packet to its intended location.