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OSI model

It is a reference model that makes it possible to describe the communication protocols used by computer networks. It is made up of 7 layers from top to bottom.

Of course, here is the list of layers of the reversed OSI model, starting with the topmost layer

Application layer (Layer number 7)

  • Direct interface for software applications.
  • Provides specific network services, such as email, file transfer and web browsing.

Presentation Layer (Layer number 6)

  • Translates data between network format and the format the application can understand.
  • Handles encryption, compression and other data transformations.

Session Layer(Layer number 5)

  • Manages communication sessions between applications.
  • Responsible for establishing, managing and terminating sessions.

Transport Layer (Layer number 4)

  • Responsible for data delivery between two hosts.
  • Manages segmentation, flow control and error correction (TCP/UDP).

Network Layer (Layer number 3)

  • Manages the routing of data packets from one node to another.
  • Uses IP addresses to identify devices on the network.

Data Link Layer (Layer number 2)

  • Responsible for reliable data transmission between two physically connected nodes.
  • Manages MAC addresses, errors, and flow control.

Physical Layer (Layer number 1)

  • Manages the transmission and reception of raw data on physical media, such as cables, optical fiber, etc.

Starting from the Application layer to the Physical layer, we travel the path from the user interface to the hardware and physical aspects of the network. It's a concept that we see in professional baccalaureate / BTS network in general, always good to know.

A simplified course and image here: https://openclassrooms.com/fr/courses/6944606-concevez-votre-reseau-tcp-ip/7236472-prenez-du-recul-sur-votre-pratique-grace-au-modele-osi