OSI Models and How They Work

An OSI Model is an Open Systems Interconnection core standard that defines the different levels that data passes through to reach the end user on a network. An OSI model defines a set of seven layers that are designed with specific responsibilities for transmitting data over a network through a set of network protocols.

OSI Model Layers

An OSI Model is designed to transmit data through the use of layers which is a design that was developed in the early 1980s for networks and network applications. Each layer in the OSI Model is responsible for supplying a specific protocol of services to the layer located above it.

  • Layers 1 and 2: A physical layer provides physical hardware for the data link layer to be able to transfer data. The physical layer is the first layer in the network and the data link layer is the second layer.
  • Layer 3: The third layer is the Network layer which is responsible for establishing the protocols and addressing to the data that is provided by the data link layer. The network layer determines how the data from the data link layer will be sent to the end user's device.
  • Layer 4: The fourth layer is the Transport layer that controls the flow of data from the Network layer. If the data is coming from more than one protocol then the Transport layer is responsible for translating the data into a single tributary to enable efficiency during transmission over the network to the receiving device.
  • Layer 5: The fifth layer is the Session layer which is responsible for taking the data from the Transport layer and establishing a connection with the end user's device. It is also responsible for maintaining the communication and then terminating communication when the data has been transported.
  • Layer 6: The sixth layer is the Presentation layer and is responsible for data translation by changing it into a standard format that is understood by the other layers of the network. It is also responsible for data encryption and representation on the network.
  • Layer 7: The seventh layer is the Application layer and is the final layer of the network which works with the operating system and the end user that is transferring files and data over the network. The application layer is the actual layer that end users interact with to perform computer related tasks and data file transfers.

The OSI Model is the primary format for the structure of a network; however, there are other models that are also used depending upon the purpose and use of the network infrastructure.

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