OSI model

· Updated · 1 min read · Networking and Delivery · Concept

The 7 layers of the OSI model #

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, TLS, MIME, JPEG, and ASCII.
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.

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