Have you ever wondered how our computers communicate with each other? From the screen you see for the 1’s and 0’s sent across the Internet, there are lots of processes and protocols used. The OSI Model is a way to better understand and visualize how your computer packages and processes information across a network.
What is the OSI Model?
The Open Systems Interconnection (OSI) Model is a conceptual model that divides computer and network communication into 7 layers. Each layer represents a different level of functionality that is handled by different components of the computer and network. These layers work together to form network communication we use every day.
While not implemented directly, the model is useful for providing a structural approach to designing a network, whether it is a small office LAN (Local Area Network) or a large-scale global network (IBM, 2024).
The 7 Layers
The layers of the OSI Model are arranged in a “top-down” manner to illustrate the different levels of abstraction in the process of transmitting information.
Layer 7: Application
The top layer is the Application layer, where data is displayed in a human-readable format on a screen. This is also where information is collected from the emails we type or forms we fill out.
Layer 6: Presentation
The data collected from the Application layer is then formatted and encrypted to ensure its security and integrity.
Layer 5: Session
The session layer is responsible for maintaining a connection with the receiving device, and carrying out authentication of both ends to ensure that the connection is secure.
Layer 4: Network
This layer handles end-to-end delivery of data by breaking down the data to be sent into smaller segments for the next layer. Verification that the data transmission was successful also occurs here.
Layer 3: Transport
The Transport layer is where segments from the previous layers are packaged into packets with the destination IP address. The route across the network is also determined here.
Layer 2: Data link
In the Data Link layer, packets are encapsulated into frames with the destination MAC address (GeeksForGeeks, 2024), in order for the data to be delivered to the correct physical device.
Layer 1: Physical
The Physical layer is where data is sent across wires in the form of electric signals.
The layout of devices in the network, or the network topology, is determined as part of the Physical layer (GeeksForGeeks, 2024).
Other Classifications: TCP/IP
The TCP/IP model is similar to the OSI model, but with fewer layers.
(GeeksForGeeks, 2024)
Although the TCP/IP model only has 4 layers, it is still useful in understanding networks and their structures. Each layer is associated with network protocols such as TCP (Transmission Control Protocol) and HTTP (Hypertext Transfer Protocol). This gives a full picture of where these protocols lie in the process of transmitting data across a network.
Works Cited
China, C.R. and Goodwin, M. (2024). OSI model. [online] Ibm.com. Available at: https://www.ibm.com/think/topics/osi-model#:~:text=The%20Open%20Systems%20Interconnection%20 [Accessed 22 Sep. 2024].
GeeksforGeeks (2017a). TCP/IP Model. [online] GeeksforGeeks. Available at: https://geeksforgeeks.org/tcp-ip-model/ [Accessed 22 Sep. 2024].
GeeksforGeeks (2017b). What is OSI Model | 7 Layers Explained. [online] GeeksforGeeks. Available at: https://www.geeksforgeeks.org/open-systems-interconnection-model-osi/ [Accessed 22 Sep. 2024].
GeeksforGeeks (2020). Difference between segments, packets and frames. [online] GeeksforGeeks. Available at: https://www.geeksforgeeks.org/difference-between-segments-packets-and-frames/ [Accessed 22 Sep. 2024].
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