Networking 102:
THE OSI MODEL BREAKDOWN

The OSI model, short for Open Systems Interconnection Model, is a standardized framework created by the International Organization for Standardization (ISO) in 1984. It was designed to help engineers, developers, and vendors understand, design, and troubleshoot network systems by breaking down the complex process of communication into seven clear, functional layers.

The Physical Layer is the lowest layer and is responsible for the actual transmission of raw bits over physical media like wires, fiber optics, or radio waves. It converts digital data into electrical, optical, or radio signals.

The Data Link Layer handles communication between two devices on the same physical link. It formats data into frames, applies MAC addressing, performs error detection, and manages flow control to ensure reliable transmission.

The Network Layer oversees the delivery of packets between different networks using logical addressing (IP). It decides the best path for data to travel from source to destination, even across multiple networks.

The Transport Layer ensures complete and accurate end-to-end delivery of data between applications. It breaks data into segments, handles error detection and correction, flow control, and chooses between TCP (reliable) or UDP (fast, no guarantee).

The Session Layer is responsible for managing and maintaining sessions between devices. It creates, maintains, and terminates communication sessions between endpoints, keeping track of dialog and recovering interruptions if needed.

The Presentation Layer acts as a translator and formatter between the application and the network. It ensures that data sent by the application layer of one system can be properly interpreted by the application layer of another.

The Application Layer is the topmost layer of the OSI model. It acts as the interface between the user's application (like a browser or email client) and the underlying network. This layer isn't the app itself, but part of the network stack that supports the app in communicating over the network.

The OSI model gives us a structured way to understand how data travels from one device to another across applications, systems, and networks. Each of the seven layers plays a specific role, from the physical transmission of bits to the interpretation of complex data formats.

We've now unpacked the model that defines how everything on the internet, from emails to video calls, moves. This isn't just theory; it's the framework behind every digital interaction you encounter.

See you soon in the next blog, where we'll continue building on this foundation.