The 7 layers of the OSI (Open Systems Interconnection) model, from bottom to top, are: Physical, Data Link, Network, Transport, Session, Presentation, and Application. This model is a conceptual framework used to understand how data moves across a network. Each layer performs specific functions, contributing to the overall communication process.
Here's a breakdown of each layer:
- Physical Layer: This is the foundation. It defines the physical characteristics of the network, such as cables, voltage levels, and data rates. It's responsible for transmitting raw bit streams over a physical medium.
- Data Link Layer: This layer provides error-free transmission of data frames between two directly connected nodes. It handles addressing, error detection, and flow control. Key protocols include Ethernet and Wi-Fi.
- Network Layer: This layer is responsible for routing data packets between different networks. It uses logical addresses (IP addresses) to determine the best path for data to travel.
- Transport Layer: This layer provides reliable and ordered delivery of data between applications. It handles segmentation, error recovery, and flow control. TCP and UDP are common protocols used at this layer.
- Session Layer: This layer manages and controls connections between applications. It establishes, maintains, and terminates sessions, handling authentication and authorization.
- Presentation Layer: This layer handles data representation and encryption/decryption. It ensures that data is presented in a format that applications can understand, regardless of the underlying system.
- Application Layer: This is the layer closest to the end user. It provides network services to applications, such as email, file transfer, and web browsing. Examples include HTTP, FTP, and SMTP.
In short, the OSI model provides a structured approach to understanding and troubleshooting network communication, breaking down the complex process into manageable layers.
