OSI Model

Understanding how data flows through a network


+ What is the OSI Model?

The OSI (Open Systems Interconnection) model is a conceptual framework that explains how data is transmitted between systems using seven logical layers.

+ Why do we need the OSI Model?

It helps engineers design, understand, and troubleshoot networks by isolating problems layer by layer.

+ Layer 7 – Application

Provides network services directly to user applications like browsers, email, and FTP.

+ Layer 6 – Presentation

Handles data formatting, encryption, and compression.

+ Layer 5 – Session

Manages sessions between communicating devices.

+ Layer 4 – Transport

Ensures reliable delivery using TCP or best-effort using UDP.

+ Layer 3 – Network

Handles routing and logical IP addressing. Routers operate here.

+ Layer 2 – Data Link

Responsible for MAC addressing, framing, and error detection.

+ Layer 1 – Physical

Deals with cables, signals, connectors, and transmission media.