The OSI model is a conceptual framework that is used to describe how a network functions. It identifies seven fundamental networking layers, from the physical hardware up to high-level software applications.
Each layer in the model handles a specific networking function. The standard helps administrators to visualize networks, isolate problems, and understand the use cases for new technologies.
| Layer | Name | Function |
|---|---|---|
| 7 | Application | Provides services to user applications, such as web browsers, email clients, file transfer programs, etc. For example, HTTP/HTTPS, SMTP, FTP, and DNS. |
| 6 | Presentation | Translates data into a format that can be understood by the application layer. Handles encryption, compression, and character encoding. For example, SSL, SCP, and NetBIOS. |
| 5 | Session | Establishes, maintains, and terminates sessions between nodes. Manages authentication and authorization. For example, RPC and NFS. |
| 4 | Transport | Provides reliable data transfer between nodes. Handles error detection, correction, and flow control. Uses protocols such as TCP and UDP. |
| 3 | Network | Routes data packets across different networks. Handles addressing and routing. Uses protocols such as IP and ICMP. |
| 2 | Data Link | Communicates between nodes that are directly connected in the same network. Handles frame synchronization and error detection. Uses protocols such as Ethernet and WiFi. |
| 1 | Physical | Transfers data as a stream of bits over a physical medium, such as a cable or wireless signal. Handles electrical signals and bit encoding. For example, Bluetooth, USB, DSL, and GSM. |
